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ca5777793e
12 Commits
| Author | SHA1 | Message | Date | |
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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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John Gallagher
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e60e158eff |
Add subcommand to wait for background zfs activity to complete
Currently the best way to wait for the completion of a long-running
operation in a pool, like a scrub or device removal, is to poll 'zpool
status' and parse its output, which is neither efficient nor convenient.
This change adds a 'wait' subcommand to the zpool command. When invoked,
'zpool wait' will block until a specified type of background activity
completes. Currently, this subcommand can wait for any of the following:
- Scrubs or resilvers to complete
- Devices to initialized
- Devices to be replaced
- Devices to be removed
- Checkpoints to be discarded
- Background freeing to complete
For example, a scrub that is in progress could be waited for by running
zpool wait -t scrub <pool>
This also adds a -w flag to the attach, checkpoint, initialize, replace,
remove, and scrub subcommands. When used, this flag makes the operations
kicked off by these subcommands synchronous instead of asynchronous.
This functionality is implemented using a new ioctl. The type of
activity to wait for is provided as input to the ioctl, and the ioctl
blocks until all activity of that type has completed. An ioctl was used
over other methods of kernel-userspace communiction primarily for the
sake of portability.
Porting Notes:
This is ported from Delphix OS change DLPX-44432. The following changes
were made while porting:
- Added ZoL-style ioctl input declaration.
- Reorganized error handling in zpool_initialize in libzfs to integrate
better with changes made for TRIM support.
- Fixed check for whether a checkpoint discard is in progress.
Previously it also waited if the pool had a checkpoint, instead of
just if a checkpoint was being discarded.
- Exposed zfs_initialize_chunk_size as a ZoL-style tunable.
- Updated more existing tests to make use of new 'zpool wait'
functionality, tests that don't exist in Delphix OS.
- Used existing ZoL tunable zfs_scan_suspend_progress, together with
zinject, in place of a new tunable zfs_scan_max_blks_per_txg.
- Added support for a non-integral interval argument to zpool wait.
Future work:
ZoL has support for trimming devices, which Delphix OS does not. In the
future, 'zpool wait' could be extended to add the ability to wait for
trim operations to complete.
Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: John Gallagher <john.gallagher@delphix.com>
Closes #9162
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Matthew Macy
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03fdcb9adc |
Make module tunables cross platform
Adds ZFS_MODULE_PARAM to abstract module parameter setting to operating systems other than Linux. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Igor Kozhukhov <igor@dilos.org> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Matt Macy <mmacy@FreeBSD.org> Signed-off-by: Ryan Moeller <ryan@ixsystems.com> Closes #9230 |
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Andrea Gelmini
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e1cfd73f7f |
Fix typos in module/zfs/
Reviewed-by: Matt Ahrens <matt@delphix.com> Reviewed-by: Ryan Moeller <ryan@ixsystems.com> Reviewed-by: Richard Laager <rlaager@wiktel.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net> Closes #9240 |
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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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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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Brian Behlendorf
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dd785b5b86
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Fix vdev_initialize_restart / removal race
Resolve a vdev_initialize crash uncovered by ztest. Similar to when starting a new initialization verify that a removal is not in progress. Additionally, do not restart when the thread already exists. This check is now congruent with the POOL_INITIALIZE_DO handling in spa_vdev_initialize_impl(). Reviewed-by: Tom Caputi <tcaputi@datto.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8477 |
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Brian Behlendorf
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96ebc5a1a4
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Fix race in vdev_initialize_thread
Before allowing new allocations to the metaslab we need to ensure that any issued initializing writes have been synced. Otherwise, it's possible for metaslab_block_alloc() to allocate a range which is about to be overwritten by an initializing IO. Serapheim Dimitropoulos <serapheim@delphix.com> Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com> Reviewed-by: Tim Chase <tim@chase2k.com> Reviewed-by: George Wilson <george.wilson@delphix.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #8461 |
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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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c10d37dd9f |
zfs initialize performance enhancements
PROBLEM ======== When invoking "zpool initialize" on a pool the command will create a thread to initialize each disk. Unfortunately, it does this serially across many transaction groups which can result in commands taking a long time to return to the user and may appear hung. The same thing is true when trying to suspend/cancel the operation. SOLUTION ========= This change refactors the way we invoke the initialize interface to ensure we can start or stop the intialization in just a few transaction groups. When stopping or cancelling a vdev initialization perform it in two phases. First signal each vdev initialization thread that it should exit, then after all threads have been signaled wait for them to exit. On a pool with 40 leaf vdevs this reduces the vdev initialize stop/cancel time from ~10 minutes to under a second. The reason for this is spa_vdev_initialize() no longer needs to wait on multiple full TXGs per leaf vdev being stopped. This commit additionally adds some missing checks for the passed "initialize_vdevs" input nvlist. The contents of the user provided input "initialize_vdevs" nvlist must be validated to ensure all values are uint64s. This is done in zfs_ioc_pool_initialize() in order to keep all of these checks in a single location. Updated the innvl and outnvl comments to match the formatting used for all other new sytle ioctls. Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed-by: loli10K <ezomori.nozomu@gmail.com> Reviewed-by: Tim Chase <tim@chase2k.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: George Wilson <george.wilson@delphix.com> Closes #8230 |
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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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