Commit Graph

8 Commits

Author SHA1 Message Date
Tino Reichardt
1d3ba0bf01
Replace dead opensolaris.org license link
The commit replaces all findings of the link:
http://www.opensolaris.org/os/licensing with this one:
https://opensource.org/licenses/CDDL-1.0

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tino Reichardt <milky-zfs@mcmilk.de>
Closes #13619
2022-07-11 14:16:13 -07:00
Andrea Gelmini
cf7c5a030e Fix typos in include/
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 #9238
2019-08-30 09:53:15 -07:00
Serapheim Dimitropoulos
e48afbc4eb OpenZFS 9464 - txg_kick() fails to see that we are quiescing
txg_kick() fails to see that we are quiescing, forcing transactions to
their next stages without leaving them accumulate changes

Creating a fragmented pool in a DCenter VM and continuously writing to it with
multiple instances of randwritecomp, we get the following output from txg.d:

    0ms   311MB in  4114ms (95% p1)  75MB/s  544MB (76%)  336us   153ms     0ms
    0ms     8MB in    51ms ( 0% p1) 163MB/s  474MB (66%)  129us    34ms     0ms
    0ms   366MB in  4454ms (93% p1)  82MB/s  572MB (79%)  498us    20ms     0ms
    0ms   406MB in  5212ms (95% p1)  77MB/s  591MB (82%)  661us    37ms     0ms
    0ms   340MB in  5110ms (94% p1)  66MB/s  622MB (86%) 1048us    41ms     1ms
    0ms     3MB in    61ms ( 0% p1)  51MB/s  419MB (58%)   33us     0ms     0ms
    0ms   361MB in  3555ms (88% p1) 101MB/s  542MB (75%)  335us    40ms     0ms
    0ms   356MB in  4592ms (92% p1)  77MB/s  561MB (78%)  430us    89ms     1ms
    0ms    11MB in   129ms (13% p1)  90MB/s  507MB (70%)  222us    15ms     0ms
    0ms   281MB in  2520ms (89% p1) 111MB/s  542MB (75%)  334us    42ms     0ms
    0ms   383MB in  3666ms (91% p1) 104MB/s  557MB (77%)  411us   133ms     0ms
    0ms   404MB in  5757ms (94% p1)  70MB/s  635MB (88%) 1274us   123ms     2ms
    4ms   367MB in  4172ms (89% p1)  88MB/s  556MB (77%)  401us    51ms     0ms
    0ms    42MB in   470ms (44% p1)  90MB/s  557MB (77%)  412us    43ms     0ms
    0ms   261MB in  2273ms (88% p1) 114MB/s  556MB (77%)  407us    27ms     0ms
    0ms   394MB in  3646ms (85% p1) 108MB/s  552MB (77%)  393us   304ms     0ms
    0ms   275MB in  2416ms (89% p1) 113MB/s  510MB (71%)  200us    53ms     0ms
    0ms     9MB in    53ms ( 0% p1) 169MB/s  483MB (67%)  140us   100ms     1ms

The TXGs that are getting synced and don't have lots of changes are pushed by
txg_kick() which basically forces the current open txg to get to the quiesced
state:

        if (tx->tx_syncing_txg == 0 &&
        tx->tx_quiesce_txg_waiting <= tx->tx_open_txg &&
        tx->tx_sync_txg_waiting <= tx->tx_synced_txg &&
        tx->tx_quiesced_txg <= tx->tx_synced_txg) {
        tx->tx_quiesce_txg_waiting = tx->tx_open_txg + 1;
        cv_broadcast(&tx->tx_quiesce_more_cv);
    }

The problem is that the above code doesn't check if we are currently quiescing
anything (only if a quiesce or a sync has been requested, ..etc) so the
following scenario can happen:

1] We have an open txg A that had enough dirty data (more than
   zfs_dirty_data_sync) and it was pushed to the quiesced state, and opened
   a new txg B. No txg is currently being synced.
2] Immediately after the opening of B, txg_kick() was run by some other write
   (and because of A's dirty data) and saw that we are not currently syncing
   any txg and no one has requested quiescing so it requests one by bumping
   tx_quiesce_txg_waiting and broadcasts the quiesce thread.
3] The quiesce thread just passed txg A to be synced and sees that a quiescing
   request has been sent to it so it immediately grabs B without letting it
   gather enough data, putting it in a quiesced state and opening a new txg C.

In this scenario txg B, is an example of how the entries of interest show up in
the txg.d output.

Ideally we would like txg_kick() to get triggered only when we are sure that
we are not syncing AND not quiescing any txg. This way we can kick an open TXG
to the quiescing state when we are sure that there is nothing going on and we
would benefit from the different states running concurrently.

Authored by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Andriy Gapon <avg@FreeBSD.org>
Approved by: Dan McDonald <danmcd@joyent.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>

OpenZFS-issue: https://illumos.org/issues/9464
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/1cd7635b
Closes #7587
2018-06-04 14:56:06 -07:00
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
2017-01-03 11:31:18 -06:00
Matthew Ahrens
e8b96c6007 Illumos #4045 write throttle & i/o scheduler performance work
4045 zfs write throttle & i/o scheduler performance work

1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync
read, sync write, async read, async write, and scrub/resilver.  The scheduler
issues a number of concurrent i/os from each class to the device.  Once a class
has been selected, an i/o is selected from this class using either an elevator
algorithem (async, scrub classes) or FIFO (sync classes).  The number of
concurrent async write i/os is tuned dynamically based on i/o load, to achieve
good sync i/o latency when there is not a high load of writes, and good write
throughput when there is.  See the block comment in vdev_queue.c (reproduced
below) for more details.

2. The write throttle (dsl_pool_tempreserve_space() and
txg_constrain_throughput()) is rewritten to produce much more consistent delays
when under constant load.  The new write throttle is based on the amount of
dirty data, rather than guesses about future performance of the system.  When
there is a lot of dirty data, each transaction (e.g. write() syscall) will be
delayed by the same small amount.  This eliminates the "brick wall of wait"
that the old write throttle could hit, causing all transactions to wait several
seconds until the next txg opens.  One of the keys to the new write throttle is
decrementing the amount of dirty data as i/o completes, rather than at the end
of spa_sync().  Note that the write throttle is only applied once the i/o
scheduler is issuing the maximum number of outstanding async writes.  See the
block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for
more details.

This diff has several other effects, including:

 * the commonly-tuned global variable zfs_vdev_max_pending has been removed;
use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead.

 * the size of each txg (meaning the amount of dirty data written, and thus the
time it takes to write out) is now controlled differently.  There is no longer
an explicit time goal; the primary determinant is amount of dirty data.
Systems that are under light or medium load will now often see that a txg is
always syncing, but the impact to performance (e.g. read latency) is minimal.
Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this.

 * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression,
checksum, etc.  This improves latency by not allowing these CPU-intensive tasks
to consume all CPU (on machines with at least 4 CPU's; the percentage is
rounded up).

--matt

APPENDIX: problems with the current i/o scheduler

The current ZFS i/o scheduler (vdev_queue.c) is deadline based.  The problem
with this is that if there are always i/os pending, then certain classes of
i/os can see very long delays.

For example, if there are always synchronous reads outstanding, then no async
writes will be serviced until they become "past due".  One symptom of this
situation is that each pass of the txg sync takes at least several seconds
(typically 3 seconds).

If many i/os become "past due" (their deadline is in the past), then we must
service all of these overdue i/os before any new i/os.  This happens when we
enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in
the future.  If we can't complete all the i/os in 2.5 seconds (e.g. because
there were always reads pending), then these i/os will become past due.  Now we
must service all the "async" writes (which could be hundreds of megabytes)
before we service any reads, introducing considerable latency to synchronous
i/os (reads or ZIL writes).

Notes on porting to ZFS on Linux:

- zio_t gained new members io_physdone and io_phys_children.  Because
  object caches in the Linux port call the constructor only once at
  allocation time, objects may contain residual data when retrieved
  from the cache. Therefore zio_create() was updated to zero out the two
  new fields.

- vdev_mirror_pending() relied on the depth of the per-vdev pending queue
  (vq->vq_pending_tree) to select the least-busy leaf vdev to read from.
  This tree has been replaced by vq->vq_active_tree which is now used
  for the same purpose.

- vdev_queue_init() used the value of zfs_vdev_max_pending to determine
  the number of vdev I/O buffers to pre-allocate.  That global no longer
  exists, so we instead use the sum of the *_max_active values for each of
  the five I/O classes described above.

- The Illumos implementation of dmu_tx_delay() delays a transaction by
  sleeping in condition variable embedded in the thread
  (curthread->t_delay_cv).  We do not have an equivalent CV to use in
  Linux, so this change replaced the delay logic with a wrapper called
  zfs_sleep_until(). This wrapper could be adopted upstream and in other
  downstream ports to abstract away operating system-specific delay logic.

- These tunables are added as module parameters, and descriptions added
  to the zfs-module-parameters.5 man page.

  spa_asize_inflation
  zfs_deadman_synctime_ms
  zfs_vdev_max_active
  zfs_vdev_async_write_active_min_dirty_percent
  zfs_vdev_async_write_active_max_dirty_percent
  zfs_vdev_async_read_max_active
  zfs_vdev_async_read_min_active
  zfs_vdev_async_write_max_active
  zfs_vdev_async_write_min_active
  zfs_vdev_scrub_max_active
  zfs_vdev_scrub_min_active
  zfs_vdev_sync_read_max_active
  zfs_vdev_sync_read_min_active
  zfs_vdev_sync_write_max_active
  zfs_vdev_sync_write_min_active
  zfs_dirty_data_max_percent
  zfs_delay_min_dirty_percent
  zfs_dirty_data_max_max_percent
  zfs_dirty_data_max
  zfs_dirty_data_max_max
  zfs_dirty_data_sync
  zfs_delay_scale

  The latter four have type unsigned long, whereas they are uint64_t in
  Illumos.  This accommodates Linux's module_param() supported types, but
  means they may overflow on 32-bit architectures.

  The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most
  likely to overflow on 32-bit systems, since they express physical RAM
  sizes in bytes.  In fact, Illumos initializes zfs_dirty_data_max_max to
  2^32 which does overflow. To resolve that, this port instead initializes
  it in arc_init() to 25% of physical RAM, and adds the tunable
  zfs_dirty_data_max_max_percent to override that percentage.  While this
  solution doesn't completely avoid the overflow issue, it should be a
  reasonable default for most systems, and the minority of affected
  systems can work around the issue by overriding the defaults.

- Fixed reversed logic in comment above zfs_delay_scale declaration.

- Clarified comments in vdev_queue.c regarding when per-queue minimums take
  effect.

- Replaced dmu_tx_write_limit in the dmu_tx kstat file
  with dmu_tx_dirty_delay and dmu_tx_dirty_over_max.  The first counts
  how many times a transaction has been delayed because the pool dirty
  data has exceeded zfs_delay_min_dirty_percent.  The latter counts how
  many times the pool dirty data has exceeded zfs_dirty_data_max (which
  we expect to never happen).

- The original patch would have regressed the bug fixed in
  zfsonlinux/zfs@c418410, which prevented users from setting the
  zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE.
  A similar fix is added to vdev_queue_aggregate().

- In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the
  heap instead of the stack.  In Linux we can't afford such large
  structures on the stack.

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Ned Bass <bass6@llnl.gov>
Reviewed by: Brendan Gregg <brendan.gregg@joyent.com>
Approved by: Robert Mustacchi <rm@joyent.com>

References:
  http://www.illumos.org/issues/4045
  illumos/illumos-gate@69962b5647

Ported-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1913
2013-12-06 09:32:43 -08:00
Adam Leventhal
63fd3c6cfd Illumos #3582, #3584
3582 zfs_delay() should support a variable resolution
3584 DTrace sdt probes for ZFS txg states

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Richard Elling <richard.elling@dey-sys.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
    https://www.illumos.org/issues/3582
    illumos/illumos-gate@0689f76

Ported by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775
2013-11-04 10:55:25 -08:00
George Wilson
2696dfafd9 Illumos #3642, #3643
3642 dsl_scan_active() should not issue I/O to determine if async
     destroying is active
3643 txg_delay should not hold the tc_lock
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Approved by: Gordon Ross <gwr@nexenta.com>

References:
  https://www.illumos.org/issues/3642
  https://www.illumos.org/issues/3643
  illumos/illumos-gate@4a92375985

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #1775

Porting Notes:

1. The alignment assumptions for the tx_cpu structure assume that
   a kmutex_t is 8 bytes.  This isn't true under Linux but tc_pad[]
   was adjusted anyway for consistency since this structure was
   never carefully aligned in ZoL.  If careful alignment does impact
   performance significantly this should be reworked to be portable.
2013-11-01 08:55:12 -07:00
Brian Behlendorf
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.
2010-09-08 12:38:56 -07:00