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30 Commits
| Author | SHA1 | Message | Date | |
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Alexander Motin
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f8020c9363
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Make metaslab class rotor and aliquot per-allocator.
Metaslab rotor and aliquot are used to distribute workload between vdevs while keeping some locality for logically adjacent blocks. Once multiple allocators were introduced to separate allocation of different objects it does not make much sense for different allocators to write into different metaslabs of the same metaslab group (vdev) same time, competing for its resources. This change makes each allocator choose metaslab group independently, colliding with others only sporadically. Test including simultaneous write into 4 files with recordsize of 4KB on a striped pool of 30 disks on a system with 40 logical cores show reduction of vdev queue lock contention from 54 to 27% due to better load distribution. Unfortunately it won't help much ZVOLs yet since only one dataset/ZVOL is synced at a time, and so for the most part only one allocator is used, but it may improve later. While there, to reduce the number of pointer dereferences change per-allocator storage for metaslab classes and groups from several separate malloc()'s to variable length arrays at the ends of the original class and group structures. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Alexander Motin <mav@FreeBSD.org> Closes #11288 |
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Matthew Ahrens
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32d805c3e2
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Use a struct to organize metaslab-group-allocator fields
Each metaslab group (of which there is one per top-level vdev) has several (4, by default) "metaslab group allocators". Each "allocator" has its own metaslab that it prefers to allocate from (the "primary" allocator), and each can perform allocations concurrently with the other allocators. In addition to the primary metaslab, there are several other fields that need to be tracked separately for each allocator. These are currently stored as several arrays in the metaslab_group_t, each array indexed by allocator number. This change organizes all the metaslab-group-allocator-specific fields into a new struct, metaslab_group_allocator_t. The metaslab_group_t now needs only one array indexed by the allocator number - which contains the metaslab_group_allocator_t's. Reviewed-by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10213 |
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Paul Dagnelie
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ca5777793e |
Reduce loaded range tree memory usage
This patch implements a new tree structure for ZFS, and uses it to
store range trees more efficiently.
The new structure is approximately a B-tree, though there are some
small differences from the usual characterizations. The tree has core
nodes and leaf nodes; each contain data elements, which the elements
in the core nodes acting as separators between its children. The
difference between core and leaf nodes is that the core nodes have an
array of children, while leaf nodes don't. Every node in the tree may
be only partially full; in most cases, they are all at least 50% full
(in terms of element count) except for the root node, which can be
less full. Underfull nodes will steal from their neighbors or merge to
remain full enough, while overfull nodes will split in two. The data
elements are contained in tree-controlled buffers; they are copied
into these on insertion, and overwritten on deletion. This means that
the elements are not independently allocated, which reduces overhead,
but also means they can't be shared between trees (and also that
pointers to them are only valid until a side-effectful tree operation
occurs). The overhead varies based on how dense the tree is, but is
usually on the order of about 50% of the element size; the per-node
overheads are very small, and so don't make a significant difference.
The trees can accept arbitrary records; they accept a size and a
comparator to allow them to be used for a variety of purposes.
The new trees replace the AVL trees used in the range trees today.
Currently, the range_seg_t structure contains three 8 byte integers
of payload and two 24 byte avl_tree_node_ts to handle its storage in
both an offset-sorted tree and a size-sorted tree (total size: 64
bytes). In the new model, the range seg structures are usually two 4
byte integers, but a separate one needs to exist for the size-sorted
and offset-sorted tree. Between the raw size, the 50% overhead, and
the double storage, the new btrees are expected to use 8*1.5*2 = 24
bytes per record, or 33.3% as much memory as the AVL trees (this is
for the purposes of storing metaslab range trees; for other purposes,
like scrubs, they use ~50% as much memory).
We reduced the size of the payload in the range segments by teaching
range trees about starting offsets and shifts; since metaslabs have a
fixed starting offset, and they all operate in terms of disk sectors,
we can store the ranges using 4-byte integers as long as the size of
the metaslab divided by the sector size is less than 2^32. For 512-byte
sectors, this is a 2^41 (or 2TB) metaslab, which with the default
settings corresponds to a 256PB disk. 4k sector disks can handle
metaslabs up to 2^46 bytes, or 2^63 byte disks. Since we do not
anticipate disks of this size in the near future, there should be
almost no cases where metaslabs need 64-byte integers to store their
ranges. We do still have the capability to store 64-byte integer ranges
to account for cases where we are storing per-vdev (or per-dnode) trees,
which could reasonably go above the limits discussed. We also do not
store fill information in the compact version of the node, since it
is only used for sorted scrub.
We also optimized the metaslab loading process in various other ways
to offset some inefficiencies in the btree model. While individual
operations (find, insert, remove_from) are faster for the btree than
they are for the avl tree, remove usually requires a find operation,
while in the AVL tree model the element itself suffices. Some clever
changes actually caused an overall speedup in metaslab loading; we use
approximately 40% less cpu to load metaslabs in our tests on Illumos.
Another memory and performance optimization was achieved by changing
what is stored in the size-sorted trees. When a disk is heavily
fragmented, the df algorithm used by default in ZFS will almost always
find a number of small regions in its initial cursor-based search; it
will usually only fall back to the size-sorted tree to find larger
regions. If we increase the size of the cursor-based search slightly,
and don't store segments that are smaller than a tunable size floor
in the size-sorted tree, we can further cut memory usage down to
below 20% of what the AVL trees store. This also results in further
reductions in CPU time spent loading metaslabs.
The 16KiB size floor was chosen because it results in substantial memory
usage reduction while not usually resulting in situations where we can't
find an appropriate chunk with the cursor and are forced to use an
oversized chunk from the size-sorted tree. In addition, even if we do
have to use an oversized chunk from the size-sorted tree, the chunk
would be too small to use for ZIL allocations, so it isn't as big of a
loss as it might otherwise be. And often, more small allocations will
follow the initial one, and the cursor search will now find the
remainder of the chunk we didn't use all of and use it for subsequent
allocations. Practical testing has shown little or no change in
fragmentation as a result of this change.
If the size-sorted tree becomes empty while the offset sorted one still
has entries, it will load all the entries from the offset sorted tree
and disregard the size floor until it is unloaded again. This operation
occurs rarely with the default setting, only on incredibly thoroughly
fragmented pools.
There are some other small changes to zdb to teach it to handle btrees,
but nothing major.
Reviewed-by: George Wilson <gwilson@delphix.com>
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed by: Sebastien Roy seb@delphix.com
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #9181
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Paul Dagnelie
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eef0f4d84e |
Keep more metaslabs loaded
With the other metaslab changes loaded onto a system, we can significantly reduce the memory usage of each loaded metaslab and unload them on demand if there is memory pressure. However, none of those changes actually result in us keeping more metaslabs loaded. If we don't keep more metaslabs loaded, we will still have to wait for demand-loading to finish when no loaded metaslab can satisfy our allocation, which can cause ZIL performance issues. In addition, performance is traditionally measured by IOs per unit time, while unloading is currently done on a txg-count basis. Txgs can take a widely varying range of times, from tenths of a second to several seconds. This can result in confusing, hard to predict behavior. This change simply adds a time-based component to metaslab unloading. A metaslab will remain loaded for one minute and 8 txgs (by default) after it was last used, unless it is evicted due to memory pressure. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Paul Dagnelie <pcd@delphix.com> External-issue: DLPX-65016 External-issue: DLPX-65047 Closes #9197 |
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Paul Dagnelie
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f09fda5071 |
Cap metaslab memory usage
On systems with large amounts of storage and high fragmentation, a huge amount of space can be used by storing metaslab range trees. Since metaslabs are only unloaded during a txg sync, and only if they have been inactive for 8 txgs, it is possible to get into a state where all of the system's memory is consumed by range trees and metaslabs, and txgs cannot sync. While ZFS knows how to evict ARC data when needed, it has no such mechanism for range tree data. This can result in boot hangs for some system configurations. First, we add the ability to unload metaslabs outside of syncing context. Second, we store a multilist of all loaded metaslabs, sorted by their selection txg, so we can quickly identify the oldest metaslabs. We use a multilist to reduce lock contention during heavy write workloads. Finally, we add logic that will unload a metaslab when we're loading a new metaslab, if we're using more than a certain fraction of the available memory on range trees. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Sebastien Roy <sebastien.roy@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #9128 |
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Paul Dagnelie
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c81f1790e2 |
Metaslab max_size should be persisted while unloaded
When we unload metaslabs today in ZFS, the cached max_size value is discarded. We instead use the histogram to determine whether or not we think we can satisfy an allocation from the metaslab. This can result in situations where, if we're doing I/Os of a size not aligned to a histogram bucket, a metaslab is loaded even though it cannot satisfy the allocation we think it can. For example, a metaslab with 16 entries in the 16k-32k bucket may have entirely 16kB entries. If we try to allocate a 24kB buffer, we will load that metaslab because we think it should be able to handle the allocation. Doing so is expensive in CPU time, disk reads, and average IO latency. This is exacerbated if the write being attempted is a sync write. This change makes ZFS cache the max_size after the metaslab is unloaded. If we ever get a free (or a coalesced group of frees) larger than the max_size, we will update it. Otherwise, we leave it as is. When attempting to allocate, we use the max_size as a lower bound, and respect it unless we are in try_hard. However, we do age the max_size out at some point, since we expect the actual max_size to increase as we do more frees. A more sophisticated algorithm here might be helpful, but this works reasonably well. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #9055 |
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Serapheim Dimitropoulos
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93e28d661e |
Log Spacemap Project
= Motivation At Delphix we've seen a lot of customer systems where fragmentation is over 75% and random writes take a performance hit because a lot of time is spend on I/Os that update on-disk space accounting metadata. Specifically, we seen cases where 20% to 40% of sync time is spend after sync pass 1 and ~30% of the I/Os on the system is spent updating spacemaps. The problem is that these pools have existed long enough that we've touched almost every metaslab at least once, and random writes scatter frees across all metaslabs every TXG, thus appending to their spacemaps and resulting in many I/Os. To give an example, assuming that every VDEV has 200 metaslabs and our writes fit within a single spacemap block (generally 4K) we have 200 I/Os. Then if we assume 2 levels of indirection, we need 400 additional I/Os and since we are talking about metadata for which we keep 2 extra copies for redundancy we need to triple that number, leading to a total of 1800 I/Os per VDEV every TXG. We could try and decrease the number of metaslabs so we have less I/Os per TXG but then each metaslab would cover a wider range on disk and thus would take more time to be loaded in memory from disk. In addition, after it's loaded, it's range tree would consume more memory. Another idea would be to just increase the spacemap block size which would allow us to fit more entries within an I/O block resulting in fewer I/Os per metaslab and a speedup in loading time. The problem is still that we don't deal with the number of I/Os going up as the number of metaslabs is increasing and the fact is that we generally write a lot to a few metaslabs and a little to the rest of them. Thus, just increasing the block size would actually waste bandwidth because we won't be utilizing our bigger block size. = About this patch This patch introduces the Log Spacemap project which provides the solution to the above problem while taking into account all the aforementioned tradeoffs. The details on how it achieves that can be found in the references sections below and in the code (see Big Theory Statement in spa_log_spacemap.c). Even though the change is fairly constraint within the metaslab and lower-level SPA codepaths, there is a side-change that is user-facing. The change is that VDEV IDs from VDEV holes will no longer be reused. To give some background and reasoning for this, when a log device is removed and its VDEV structure was replaced with a hole (or was compacted; if at the end of the vdev array), its vdev_id could be reused by devices added after that. Now with the pool-wide space maps recording the vdev ID, this behavior can cause problems (e.g. is this entry referring to a segment in the new vdev or the removed log?). Thus, to simplify things the ID reuse behavior is gone and now vdev IDs for top-level vdevs are truly unique within a pool. = Testing The illumos implementation of this feature has been used internally for a year and has been in production for ~6 months. For this patch specifically there don't seem to be any regressions introduced to ZTS and I have been running zloop for a week without any related problems. = Performance Analysis (Linux Specific) All performance results and analysis for illumos can be found in the links of the references. Redoing the same experiments in Linux gave similar results. Below are the specifics of the Linux run. After the pool reached stable state the percentage of the time spent in pass 1 per TXG was 64% on average for the stock bits while the log spacemap bits stayed at 95% during the experiment (graph: sdimitro.github.io/img/linux-lsm/PercOfSyncInPassOne.png). Sync times per TXG were 37.6 seconds on average for the stock bits and 22.7 seconds for the log spacemap bits (related graph: sdimitro.github.io/img/linux-lsm/SyncTimePerTXG.png). As a result the log spacemap bits were able to push more TXGs, which is also the reason why all graphs quantified per TXG have more entries for the log spacemap bits. Another interesting aspect in terms of txg syncs is that the stock bits had 22% of their TXGs reach sync pass 7, 55% reach sync pass 8, and 20% reach 9. The log space map bits reached sync pass 4 in 79% of their TXGs, sync pass 7 in 19%, and sync pass 8 at 1%. This emphasizes the fact that not only we spend less time on metadata but we also iterate less times to convergence in spa_sync() dirtying objects. [related graphs: stock- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGStock.png lsm- sdimitro.github.io/img/linux-lsm/NumberOfPassesPerTXGLSM.png] Finally, the improvement in IOPs that the userland gains from the change is approximately 40%. There is a consistent win in IOPS as you can see from the graphs below but the absolute amount of improvement that the log spacemap gives varies within each minute interval. sdimitro.github.io/img/linux-lsm/StockVsLog3Days.png sdimitro.github.io/img/linux-lsm/StockVsLog10Hours.png = Porting to Other Platforms For people that want to port this commit to other platforms below is a list of ZoL commits that this patch depends on: Make zdb results for checkpoint tests consistent |
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Brian Behlendorf
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1b939560be
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Add TRIM support
UNMAP/TRIM support is a frequently-requested feature to help prevent performance from degrading on SSDs and on various other SAN-like storage back-ends. By issuing UNMAP/TRIM commands for sectors which are no longer allocated the underlying device can often more efficiently manage itself. This TRIM implementation is modeled on the `zpool initialize` feature which writes a pattern to all unallocated space in the pool. The new `zpool trim` command uses the same vdev_xlate() code to calculate what sectors are unallocated, the same per- vdev TRIM thread model and locking, and the same basic CLI for a consistent user experience. The core difference is that instead of writing a pattern it will issue UNMAP/TRIM commands for those extents. The zio pipeline was updated to accommodate this by adding a new ZIO_TYPE_TRIM type and associated spa taskq. This new type makes is straight forward to add the platform specific TRIM/UNMAP calls to vdev_disk.c and vdev_file.c. These new ZIO_TYPE_TRIM zios are handled largely the same way as ZIO_TYPE_READs or ZIO_TYPE_WRITEs. This makes it possible to largely avoid changing the pipieline, one exception is that TRIM zio's may exceed the 16M block size limit since they contain no data. In addition to the manual `zpool trim` command, a background automatic TRIM was added and is controlled by the 'autotrim' property. It relies on the exact same infrastructure as the manual TRIM. However, instead of relying on the extents in a metaslab's ms_allocatable range tree, a ms_trim tree is kept per metaslab. When 'autotrim=on', ranges added back to the ms_allocatable tree are also added to the ms_free tree. The ms_free tree is then periodically consumed by an autotrim thread which systematically walks a top level vdev's metaslabs. Since the automatic TRIM will skip ranges it considers too small there is value in occasionally running a full `zpool trim`. This may occur when the freed blocks are small and not enough time was allowed to aggregate them. An automatic TRIM and a manual `zpool trim` may be run concurrently, in which case the automatic TRIM will yield to the manual TRIM. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Contributions-by: Saso Kiselkov <saso.kiselkov@nexenta.com> Contributions-by: Tim Chase <tim@chase2k.com> Contributions-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8419 Closes #598 |
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Serapheim Dimitropoulos
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928e8ad47d |
Introduce auxiliary metaslab histograms
This patch introduces 3 new histograms per metaslab. These histograms track segments that have made it to the metaslab's space map histogram (and are part of the spacemap) but have not yet reached the ms_allocatable tree on loaded metaslab's because these metaslab's are currently syncing and haven't gone through metaslab_sync_done() yet. The histograms help when we decide whether to load an unloaded metaslab in-order to allocate from it. When calculating the weight of an unloaded metaslab traditionally, we look at the highest bucket of its spacemap's histogram. The problem is that we are not guaranteed to be able to allocated that segment when we load the metaslab because it may still be at the freeing, freed, or defer trees. The new histograms are used when we try to calculate an unloaded metaslab's weight to deal with this issue by removing segments that have would not be in the allocatable tree at runtime. Note, that this method of dealing with this is not completely accurate as adjacent segments are not always consolidated in the space map histogram of a metaslab. In addition and to make things deterministic, we always reset the weight of unloaded metaslabs based on their space map weight (instead of doing that on a need basis). Thus, every time a metaslab is loaded and its weight is reset again (from the weight based on its space map to the one based on its allocatable range tree) we expect (and assert) that this change in weight can only get better if it doesn't stay the same. Reviewed by: Paul Dagnelie <pcd@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Matt Ahrens <mahrens@delphix.com> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8358 |
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Serapheim Dimitropoulos
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425d3237ee |
Get rid of space_map_update() for ms_synced_length
Initially, metaslabs and space maps used to be the same thing in ZFS. Later, we started differentiating them by referring to the space map as the on-disk state of the metaslab, making the metaslab a higher-level concept that is metadata that deals with space accounting. Today we've managed to split that code furthermore, with the space map being its own on-disk data structure used in areas of ZFS besides metaslabs (e.g. the vdev-wide space maps used for zpool checkpoint or vdev removal features). This patch refactors the space map code to further split the space map code from the metaslab code. It does so by getting rid of the idea that the space map can have a different in-core and on-disk length (sm_length vs smp_length) which is something that is only used for the metaslab code, and other consumers of space maps just have to deal with. Instead, this patch introduces changes that move the old in-core length of the metaslab's space map to the metaslab structure itself (see ms_synced_length field) while making the space map code only care about the actual space map's length on-disk. The result of this is that space map consumers no longer have to deal with syncing two different lengths for the same structure (e.g. space_map_update() goes away) while metaslab specific behavior stays within the metaslab code. Specifically, the ms_synced_length field keeps track of the amount of data metaslab_load() can read from the metaslab's space map while working concurrently with metaslab_sync() that may be appending to that same space map. As a side note, the patch also adds a few comments around the metaslab code documenting some assumptions and expected behavior. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8328 |
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Serapheim Dimitropoulos
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b194fab0fb |
Factor metaslab_load_wait() in metaslab_load()
Most callers that need to operate on a loaded metaslab, always call metaslab_load_wait() before loading the metaslab just in case someone else is already doing the work. Factoring metaslab_load_wait() within metaslab_load() makes the later more robust, as callers won't have to do the load-wait check explicitly every time they need to load a metaslab. Reviewed-by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Serapheim Dimitropoulos <serapheim@delphix.com> Closes #8290 |
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George Wilson
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619f097693 |
OpenZFS 9102 - zfs should be able to initialize storage devices
PROBLEM
========
The first access to a block incurs a performance penalty on some platforms
(e.g. AWS's EBS, VMware VMDKs). Therefore we recommend that volumes are
"thick provisioned", where supported by the platform (VMware). This can
create a large delay in getting a new virtual machines up and running (or
adding storage to an existing Engine). If the thick provision step is
omitted, write performance will be suboptimal until all blocks on the LUN
have been written.
SOLUTION
=========
This feature introduces a way to 'initialize' the disks at install or in the
background to make sure we don't incur this first read penalty.
When an entire LUN is added to ZFS, we make all space available immediately,
and allow ZFS to find unallocated space and zero it out. This works with
concurrent writes to arbitrary offsets, ensuring that we don't zero out
something that has been (or is in the middle of being) written. This scheme
can also be applied to existing pools (affecting only free regions on the
vdev). Detailed design:
- new subcommand:zpool initialize [-cs] <pool> [<vdev> ...]
- start, suspend, or cancel initialization
- Creates new open-context thread for each vdev
- Thread iterates through all metaslabs in this vdev
- Each metaslab:
- select a metaslab
- load the metaslab
- mark the metaslab as being zeroed
- walk all free ranges within that metaslab and translate
them to ranges on the leaf vdev
- issue a "zeroing" I/O on the leaf vdev that corresponds to
a free range on the metaslab we're working on
- continue until all free ranges for this metaslab have been
"zeroed"
- reset/unmark the metaslab being zeroed
- if more metaslabs exist, then repeat above tasks.
- if no more metaslabs, then we're done.
- progress for the initialization is stored on-disk in the vdev’s
leaf zap object. The following information is stored:
- the last offset that has been initialized
- the state of the initialization process (i.e. active,
suspended, or canceled)
- the start time for the initialization
- progress is reported via the zpool status command and shows
information for each of the vdevs that are initializing
Porting notes:
- Added zfs_initialize_value module parameter to set the pattern
written by "zpool initialize".
- Added zfs_vdev_{initializing,removal}_{min,max}_active module options.
Authored by: George Wilson <george.wilson@delphix.com>
Reviewed by: John Wren Kennedy <john.kennedy@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: loli10K <ezomori.nozomu@gmail.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Richard Lowe <richlowe@richlowe.net>
Signed-off-by: Tim Chase <tim@chase2k.com>
Ported-by: Tim Chase <tim@chase2k.com>
OpenZFS-issue: https://www.illumos.org/issues/9102
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/c3963210eb
Closes #8230
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Tim Schumacher
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c13060e478 |
Linux 4.19-rc3+ compat: Remove refcount_t compat
torvalds/linux@59b57717f ("blkcg: delay blkg destruction until after writeback has finished") added a refcount_t to the blkcg structure. Due to the refcount_t compatibility code, zfs_refcount_t was used by mistake. Resolve this by removing the compatibility code and replacing the occurrences of refcount_t with zfs_refcount_t. Reviewed-by: Franz Pletz <fpletz@fnordicwalking.de> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tim Schumacher <timschumi@gmx.de> Closes #7885 Closes #7932 |
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Paul Dagnelie
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492f64e941 |
OpenZFS 9112 - Improve allocation performance on high-end systems
Overview ======== We parallelize the allocation process by creating the concept of "allocators". There are a certain number of allocators per metaslab group, defined by the value of a tunable at pool open time. Each allocator for a given metaslab group has up to 2 active metaslabs; one "primary", and one "secondary". The primary and secondary weight mean the same thing they did in in the pre-allocator world; primary metaslabs are used for most allocations, secondary metaslabs are used for ditto blocks being allocated in the same metaslab group. There is also the CLAIM weight, which has been separated out from the other weights, but that is less important to understanding the patch. The active metaslabs for each allocator are moved from their normal place in the metaslab tree for the group to the back of the tree. This way, they will not be selected for use by other allocators searching for new metaslabs unless all the passive metaslabs are unsuitable for allocations. If that does happen, the allocators will "steal" from each other to ensure that IOs don't fail until there is truly no space left to perform allocations. In addition, the alloc queue for each metaslab group has been broken into a separate queue for each allocator. We don't want to dramatically increase the number of inflight IOs on low-end systems, because it can significantly increase txg times. On the other hand, we want to ensure that there are enough IOs for each allocator to allow for good coalescing before sending the IOs to the disk. As a result, we take a compromise path; each allocator's alloc queue max depth starts at a certain value for every txg. Every time an IO completes, we increase the max depth. This should hopefully provide a good balance between the two failure modes, while not dramatically increasing complexity. We also parallelize the spa_alloc_tree and spa_alloc_lock, which cause very similar contention when selecting IOs to allocate. This parallelization uses the same allocator scheme as metaslab selection. Performance Results =================== Performance improvements from this change can vary significantly based on the number of CPUs in the system, whether or not the system has a NUMA architecture, the speed of the drives, the values for the various tunables, and the workload being performed. For an fio async sequential write workload on a 24 core NUMA system with 256 GB of RAM and 8 128 GB SSDs, there is a roughly 25% performance improvement. Future Work =========== Analysis of the performance of the system with this patch applied shows that a significant new bottleneck is the vdev disk queues, which also need to be parallelized. Prototyping of this change has occurred, and there was a performance improvement, but more work needs to be done before its stability has been verified and it is ready to be upstreamed. Authored by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com> Reviewed by: Alexander Motin <mav@FreeBSD.org> Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov> Approved by: Gordon Ross <gwr@nexenta.com> Ported-by: Paul Dagnelie <pcd@delphix.com> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Porting Notes: * Fix reservation test failures by increasing tolerance. OpenZFS-issue: https://illumos.org/issues/9112 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/3f3cc3c3 Closes #7682 |
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Serapheim Dimitropoulos
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d2734cce68 |
OpenZFS 9166 - zfs storage pool checkpoint
Details about the motivation of this feature and its usage can
be found in this blogpost:
https://sdimitro.github.io/post/zpool-checkpoint/
A lightning talk of this feature can be found here:
https://www.youtube.com/watch?v=fPQA8K40jAM
Implementation details can be found in big block comment of
spa_checkpoint.c
Side-changes that are relevant to this commit but not explained
elsewhere:
* renames members of "struct metaslab trees to be shorter without
losing meaning
* space_map_{alloc,truncate}() accept a block size as a
parameter. The reason is that in the current state all space
maps that we allocate through the DMU use a global tunable
(space_map_blksz) which defauls to 4KB. This is ok for metaslab
space maps in terms of bandwirdth since they are scattered all
over the disk. But for other space maps this default is probably
not what we want. Examples are device removal's vdev_obsolete_sm
or vdev_chedkpoint_sm from this review. Both of these have a
1:1 relationship with each vdev and could benefit from a bigger
block size.
Porting notes:
* The part of dsl_scan_sync() which handles async destroys has
been moved into the new dsl_process_async_destroys() function.
* Remove "VERIFY(!(flags & FWRITE))" in "kernel.c" so zhack can write
to block device backed pools.
* ZTS:
* Fix get_txg() in zpool_sync_001_pos due to "checkpoint_txg".
* Don't use large dd block sizes on /dev/urandom under Linux in
checkpoint_capacity.
* Adopt Delphix-OS's setting of 4 (spa_asize_inflation =
SPA_DVAS_PER_BP + 1) for the checkpoint_capacity test to speed
its attempts to fill the pool
* Create the base and nested pools with sync=disabled to speed up
the "setup" phase.
* Clear labels in test pool between checkpoint tests to avoid
duplicate pool issues.
* The import_rewind_device_replaced test has been marked as "known
to fail" for the reasons listed in its DISCLAIMER.
* New module parameters:
zfs_spa_discard_memory_limit,
zfs_remove_max_bytes_pause (not documented - debugging only)
vdev_max_ms_count (formerly metaslabs_per_vdev)
vdev_min_ms_count
Authored by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Richard Lowe <richlowe@richlowe.net>
Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
OpenZFS-issue: https://illumos.org/issues/9166
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7159fdb8
Closes #7570
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Matthew Ahrens
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a1d477c24c |
OpenZFS 7614, 9064 - zfs device evacuation/removal
OpenZFS 7614 - zfs device evacuation/removal
OpenZFS 9064 - remove_mirror should wait for device removal to complete
This project allows top-level vdevs to be removed from the storage pool
with "zpool remove", reducing the total amount of storage in the pool.
This operation copies all allocated regions of the device to be removed
onto other devices, recording the mapping from old to new location.
After the removal is complete, read and free operations to the removed
(now "indirect") vdev must be remapped and performed at the new location
on disk. The indirect mapping table is kept in memory whenever the pool
is loaded, so there is minimal performance overhead when doing operations
on the indirect vdev.
The size of the in-memory mapping table will be reduced when its entries
become "obsolete" because they are no longer used by any block pointers
in the pool. An entry becomes obsolete when all the blocks that use
it are freed. An entry can also become obsolete when all the snapshots
that reference it are deleted, and the block pointers that reference it
have been "remapped" in all filesystems/zvols (and clones). Whenever an
indirect block is written, all the block pointers in it will be "remapped"
to their new (concrete) locations if possible. This process can be
accelerated by using the "zfs remap" command to proactively rewrite all
indirect blocks that reference indirect (removed) vdevs.
Note that when a device is removed, we do not verify the checksum of
the data that is copied. This makes the process much faster, but if it
were used on redundant vdevs (i.e. mirror or raidz vdevs), it would be
possible to copy the wrong data, when we have the correct data on e.g.
the other side of the mirror.
At the moment, only mirrors and simple top-level vdevs can be removed
and no removal is allowed if any of the top-level vdevs are raidz.
Porting Notes:
* Avoid zero-sized kmem_alloc() in vdev_compact_children().
The device evacuation code adds a dependency that
vdev_compact_children() be able to properly empty the vdev_child
array by setting it to NULL and zeroing vdev_children. Under Linux,
kmem_alloc() and related functions return a sentinel pointer rather
than NULL for zero-sized allocations.
* Remove comment regarding "mpt" driver where zfs_remove_max_segment
is initialized to SPA_MAXBLOCKSIZE.
Change zfs_condense_indirect_commit_entry_delay_ticks to
zfs_condense_indirect_commit_entry_delay_ms for consistency with
most other tunables in which delays are specified in ms.
* ZTS changes:
Use set_tunable rather than mdb
Use zpool sync as appropriate
Use sync_pool instead of sync
Kill jobs during test_removal_with_operation to allow unmount/export
Don't add non-disk names such as "mirror" or "raidz" to $DISKS
Use $TEST_BASE_DIR instead of /tmp
Increase HZ from 100 to 1000 which is more common on Linux
removal_multiple_indirection.ksh
Reduce iterations in order to not time out on the code
coverage builders.
removal_resume_export:
Functionally, the test case is correct but there exists a race
where the kernel thread hasn't been fully started yet and is
not visible. Wait for up to 1 second for the removal thread
to be started before giving up on it. Also, increase the
amount of data copied in order that the removal not finish
before the export has a chance to fail.
* MMP compatibility, the concept of concrete versus non-concrete devices
has slightly changed the semantics of vdev_writeable(). Update
mmp_random_leaf_impl() accordingly.
* Updated dbuf_remap() to handle the org.zfsonlinux:large_dnode pool
feature which is not supported by OpenZFS.
* Added support for new vdev removal tracepoints.
* Test cases removal_with_zdb and removal_condense_export have been
intentionally disabled. When run manually they pass as intended,
but when running in the automated test environment they produce
unreliable results on the latest Fedora release.
They may work better once the upstream pool import refectoring is
merged into ZoL at which point they will be re-enabled.
Authored by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Alex Reece <alex@delphix.com>
Reviewed-by: George Wilson <george.wilson@delphix.com>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Richard Laager <rlaager@wiktel.com>
Reviewed by: Tim Chase <tim@chase2k.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Garrett D'Amore <garrett@damore.org>
Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Tim Chase <tim@chase2k.com>
OpenZFS-issue: https://www.illumos.org/issues/7614
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/f539f1eb
Closes #6900
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Tim Chase
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258553d3d7 |
OpenZFS 7613 - ms_freetree[4] is only used in syncing context
metaslab_t:ms_freetree[TXG_SIZE] is only used in syncing context. We should replace it with two trees: the freeing tree (ranges that we are freeing this syncing txg) and the freed tree (ranges which have been freed this txg). Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Tim Chase <tim@chase2k.com> OpenZFS-issue: https://www.illumos.org/issues/7613 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/a8698da2 Closes #5598 |
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Don Brady
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4e21fd060a |
OpenZFS 7303 - dynamic metaslab selection
This change introduces a new weighting algorithm to improve metaslab selection. The new weighting algorithm relies on the SPACEMAP_HISTOGRAM feature. As a result, the metaslab weight now encodes the type of weighting algorithm used (size-based vs segment-based). Porting Notes: The metaslab allocation tracing code is conditionally removed on linux (dependent on mdb debugger). Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Chris Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Pavel Zakharov pavel.zakharov@delphix.com Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Don Brady <don.brady@intel.com> OpenZFS-issue: https://www.illumos.org/issues/7303 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/d5190931bd Closes #5404 |
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ka7
|
4e33ba4c38 |
Fix spelling
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>> Reviewed-by: George Melikov <mail@gmelikov.ru> Reviewed-by: Haakan T Johansson <f96hajo@chalmers.se> Closes #5547 Closes #5543 |
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Don Brady
|
3dfb57a35e |
OpenZFS 7090 - zfs should throttle allocations
OpenZFS 7090 - zfs should throttle allocations Authored by: George Wilson <george.wilson@delphix.com> Reviewed by: Alex Reece <alex@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com> Reviewed by: Prakash Surya <prakash.surya@delphix.com> Reviewed by: Sebastien Roy <sebastien.roy@delphix.com> Approved by: Matthew Ahrens <mahrens@delphix.com> Ported-by: Don Brady <don.brady@intel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> When write I/Os are issued, they are issued in block order but the ZIO pipeline will drive them asynchronously through the allocation stage which can result in blocks being allocated out-of-order. It would be nice to preserve as much of the logical order as possible. In addition, the allocations are equally scattered across all top-level VDEVs but not all top-level VDEVs are created equally. The pipeline should be able to detect devices that are more capable of handling allocations and should allocate more blocks to those devices. This allows for dynamic allocation distribution when devices are imbalanced as fuller devices will tend to be slower than empty devices. The change includes a new pool-wide allocation queue which would throttle and order allocations in the ZIO pipeline. The queue would be ordered by issued time and offset and would provide an initial amount of allocation of work to each top-level vdev. The allocation logic utilizes a reservation system to reserve allocations that will be performed by the allocator. Once an allocation is successfully completed it's scheduled on a given top-level vdev. Each top-level vdev maintains a maximum number of allocations that it can handle (mg_alloc_queue_depth). The pool-wide reserved allocations (top-levels * mg_alloc_queue_depth) are distributed across the top-level vdevs metaslab groups and round robin across all eligible metaslab groups to distribute the work. As top-levels complete their work, they receive additional work from the pool-wide allocation queue until the allocation queue is emptied. OpenZFS-issue: https://www.illumos.org/issues/7090 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/4756c3d7 Closes #5258 Porting Notes: - Maintained minimal stack in zio_done - Preserve linux-specific io sizes in zio_write_compress - Added module params and documentation - Updated to use optimize AVL cmp macros |
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Richard Yao
|
b10695c8f1 |
Remove fastwrite mutex
The fast write mutex is intended to protect accounting, but it is redundant because all accounting is performed through atomic operations. It also serializes all metaslab IO behind a mutex, which introduces a theoretical scaling regression that the Illumos developers did not like when we showed this to them. Removing it makes the selection of the metaslab_group lock free as it is on Illumos. The selection is not quite the same without the lock because the loop races with IO completions, but any imbalances caused by this are likely to be corrected by subsequent metaslab group selections. Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3643 |
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George Wilson
|
f3a7f6610f |
Illumos 4976-4984 - metaslab improvements
4976 zfs should only avoid writing to a failing non-redundant top-level vdev 4978 ztest fails in get_metaslab_refcount() 4979 extend free space histogram to device and pool 4980 metaslabs should have a fragmentation metric 4981 remove fragmented ops vector from block allocator 4982 space_map object should proactively upgrade when feature is enabled 4983 need to collect metaslab information via mdb 4984 device selection should use fragmentation metric Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <adam.leventhal@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> References: https://www.illumos.org/issues/4976 https://www.illumos.org/issues/4978 https://www.illumos.org/issues/4979 https://www.illumos.org/issues/4980 https://www.illumos.org/issues/4981 https://www.illumos.org/issues/4982 https://www.illumos.org/issues/4983 https://www.illumos.org/issues/4984 https://github.com/illumos/illumos-gate/commit/2e4c998 Notes: The "zdb -M" option has been re-tasked to display the new metaslab fragmentation metric and the new "zdb -I" option is used to control the maximum number of in-flight I/Os. The new fragmentation metric is derived from the space map histogram which has been rolled up to the vdev and pool level and is presented to the user via "zpool list". Add a number of module parameters related to the new metaslab weighting logic. Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2595 |
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George Wilson
|
672692c7b7 |
Illumos 4754, 4755
4754 io issued to near-full luns even after setting noalloc threshold 4755 mg_alloc_failures is no longer needed Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Dan McDonald <danmcd@omniti.com> Approved by: Dan McDonald <danmcd@omniti.com> References: https://www.illumos.org/issues/4754 https://www.illumos.org/issues/4755 https://github.com/illumos/illumos-gate/commit/b6240e8 Ported by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #2533 |
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George Wilson
|
93cf20764a |
Illumos #4101, #4102, #4103, #4105, #4106
4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Sebastien Roy <seb@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Prior to this patch, space_maps were preferred solely based on the
amount of free space left in each. Unfortunately, this heuristic didn't
contain any information about the make-up of that free space, which
meant we could keep preferring and loading a highly fragmented space map
that wouldn't actually have enough contiguous space to satisfy the
allocation; then unloading that space_map and repeating the process.
This change modifies the space_map's to store additional information
about the contiguous space in the space_map, so that we can use this
information to make a better decision about which space_map to load.
This requires reallocating all space_map objects to increase their
bonus buffer size sizes enough to fit the new metadata.
The above feature can be enabled via a new feature flag introduced by
this change: com.delphix:spacemap_histogram
In addition to the above, this patch allows the space_map block size to
be increase. Currently the block size is set to be 4K in size, which has
certain implications including the following:
* 4K sector devices will not see any compression benefit
* large space_maps require more metadata on-disk
* large space_maps require more time to load (typically random reads)
Now the space_map block size can adjust as needed up to the maximum size
set via the space_map_max_blksz variable.
A bug was fixed which resulted in potentially leaking an object when
removing a mirrored log device. The previous logic for vdev_remove() did
not deal with removing top-level vdevs that are interior vdevs (i.e.
mirror) correctly. The problem would occur when removing a mirrored log
device, and result in the DTL space map object being leaked; because
top-level vdevs don't have DTL space map objects associated with them.
References:
https://www.illumos.org/issues/4101
https://www.illumos.org/issues/4102
https://www.illumos.org/issues/4103
https://www.illumos.org/issues/4105
https://www.illumos.org/issues/4106
https://github.com/illumos/illumos-gate/commit/0713e23
Porting notes:
A handful of kmem_alloc() calls were converted to kmem_zalloc(). Also,
the KM_PUSHPAGE and TQ_PUSHPAGE flags were used as necessary.
Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2488
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George Wilson
|
ac72fac3ea |
Illumos #3954, #4080, #4081
3954 metaslabs continue to load even after hitting zfs_mg_alloc_failure limit 4080 zpool clear fails to clear pool 4081 need zfs_mg_noalloc_threshold Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: https://www.illumos.org/issues/3954 https://www.illumos.org/issues/4080 https://www.illumos.org/issues/4081 illumos/illumos-gate@22e30981d8 Ported-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #1775 |
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George Wilson
|
e51be06697 |
Illumos #3552, #3564
3552 condensing one space map burns 3 seconds of CPU in spa_sync() thread 3564 spa_sync() spends 5-10% of its time in metaslab_sync() (when not condensing) Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Dan Kimmel <dan.kimmel@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Richard Lowe <richlowe@richlowe.net> References: illumos/illumos-gate@16a4a80742 https://www.illumos.org/issues/3552 https://www.illumos.org/issues/3564 Ported-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1513 |
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George Wilson
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55d85d5a8c |
Illumos #3329, #3330, #3331, #3335
3329 spa_sync() spends 10-20% of its time in spa_free_sync_cb() 3330 space_seg_t should have its own kmem_cache 3331 deferred frees should happen after sync_pass 1 3335 make SYNC_PASS_* constants tunable Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: Matt Ahrens <matthew.ahrens@delphix.com> Reviewed by: Christopher Siden <chris.siden@delphix.com> Reviewed by: Eric Schrock <eric.schrock@delphix.com> Reviewed by: Richard Lowe <richlowe@richlowe.net> Reviewed by: Dan McDonald <danmcd@nexenta.com> Approved by: Eric Schrock <eric.schrock@delphix.com> References: illumos/illumos-gate@01f55e48fb https://www.illumos.org/issues/3329 https://www.illumos.org/issues/3330 https://www.illumos.org/issues/3331 https://www.illumos.org/issues/3335 Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> |
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Etienne Dechamps
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920dd524fb |
Add FASTWRITE algorithm for synchronous writes.
Currently, ZIL blocks are spread over vdevs using hint block pointers managed by the ZIL commit code and passed to metaslab_alloc(). Spreading log blocks accross vdevs is important for performance: indeed, using mutliple disks in parallel decreases the ZIL commit latency, which is the main performance metric for synchronous writes. However, the current implementation suffers from the following issues: 1) It would be best if the ZIL module was not aware of such low-level details. They should be handled by the ZIO and metaslab modules; 2) Because the hint block pointer is managed per log, simultaneous commits from multiple logs might use the same vdevs at the same time, which is inefficient; 3) Because dmu_write() does not honor the block pointer hint, indirect writes are not spread. The naive solution of rotating the metaslab rotor each time a block is allocated for the ZIL or dmu_sync() doesn't work in practice because the first ZIL block to be written is actually allocated during the previous commit. Consequently, when metaslab_alloc() decides the vdev for this block, it will do so while a bunch of other allocations are happening at the same time (from dmu_sync() and other ZILs). This means the vdev for this block is chosen more or less at random. When the next commit happens, there is a high chance (especially when the number of blocks per commit is slightly less than the number of the disks) that one disk will have to write two blocks (with a potential seek) while other disks are sitting idle, which defeats spreading and increases the commit latency. This commit introduces a new concept in the metaslab allocator: fastwrites. Basically, each top-level vdev maintains a counter indicating the number of synchronous writes (from dmu_sync() and the ZIL) which have been allocated but not yet completed. When the metaslab is called with the FASTWRITE flag, it will choose the vdev with the least amount of pending synchronous writes. If there are multiple vdevs with the same value, the first matching vdev (starting from the rotor) is used. Once metaslab_alloc() has decided which vdev the block is allocated to, it updates the fastwrite counter for this vdev. The rationale goes like this: when an allocation is done with FASTWRITE, it "reserves" the vdev until the data is written. Until then, all future allocations will naturally avoid this vdev, even after a full rotation of the rotor. As a result, pending synchronous writes at a given point in time will be nicely spread over all vdevs. This contrasts with the previous algorithm, which is based on the implicit assumption that blocks are written instantaneously after they're allocated. metaslab_fastwrite_mark() and metaslab_fastwrite_unmark() are used to manually increase or decrease fastwrite counters, respectively. They should be used with caution, as there is no per-BP tracking of fastwrite information, so leaks and "double-unmarks" are possible. There is, however, an assert in the vdev teardown code which will fire if the fastwrite counters are not zero when the pool is exported or the vdev removed. Note that as stated above, marking is also done implictly by metaslab_alloc(). ZIO also got a new FASTWRITE flag; when it is used, ZIO will pass it to the metaslab when allocating (assuming ZIO does the allocation, which is only true in the case of dmu_sync). This flag will also trigger an unmark when zio_done() fires. A side-effect of the new algorithm is that when a ZIL stops being used, its last block can stay in the pending state (allocated but not yet written) for a long time, polluting the fastwrite counters. To avoid that, I've implemented a somewhat crude but working solution which unmarks these pending blocks in zil_sync(), thus guaranteeing that linguering fastwrites will get pruned at each sync event. The best performance improvements are observed with pools using a large number of top-level vdevs and heavy synchronous write workflows (especially indirect writes and concurrent writes from multiple ZILs). Real-life testing shows a 200% to 300% performance increase with indirect writes and various commit sizes. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #1013 |
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George Wilson
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6d974228ef |
Illumos #1051: zfs should handle imbalanced luns
Today zfs tries to allocate blocks evenly across all devices. This means when devices are imbalanced zfs will use lots of CPU searching for space on devices which tend to be pretty full. It should instead fail quickly on the full LUNs and move onto devices which have more availability. Reviewed by: Eric Schrock <Eric.Schrock@delphix.com> Reviewed by: Matt Ahrens <Matt.Ahrens@delphix.com> Reviewed by: Adam Leventhal <Adam.Leventhal@delphix.com> Reviewed by: Albert Lee <trisk@nexenta.com> Reviewed by: Gordon Ross <gwr@nexenta.com> Approved by: Garrett D'Amore <garrett@nexenta.com> References to Illumos issue and patch: - https://www.illumos.org/issues/510 - https://github.com/illumos/illumos-gate/commit/5ead3ed965 Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #340 |
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Brian Behlendorf
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6283f55ea1 |
Support custom build directories and move includes
One of the neat tricks an autoconf style project is capable of is allow configurion/building in a directory other than the source directory. The major advantage to this is that you can build the project various different ways while making changes in a single source tree. For example, this project is designed to work on various different Linux distributions each of which work slightly differently. This means that changes need to verified on each of those supported distributions perferably before the change is committed to the public git repo. Using nfs and custom build directories makes this much easier. I now have a single source tree in nfs mounted on several different systems each running a supported distribution. When I make a change to the source base I suspect may break things I can concurrently build from the same source on all the systems each in their own subdirectory. wget -c http://github.com/downloads/behlendorf/zfs/zfs-x.y.z.tar.gz tar -xzf zfs-x.y.z.tar.gz cd zfs-x-y-z ------------------------- run concurrently ---------------------- <ubuntu system> <fedora system> <debian system> <rhel6 system> mkdir ubuntu mkdir fedora mkdir debian mkdir rhel6 cd ubuntu cd fedora cd debian cd rhel6 ../configure ../configure ../configure ../configure make make make make make check make check make check make check This change also moves many of the include headers from individual incude/sys directories under the modules directory in to a single top level include directory. This has the advantage of making the build rules cleaner and logically it makes a bit more sense. |