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Illumos 4753 - increase number of outstanding async writes when sync task is waiting 

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
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: Dan McDonald <danmcd@omniti.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
    https://www.illumos.org/issues/4753
    https://github.com/illumos/illumos-gate/commit/73527f4

Comments by Matt Ahrens from the issue tracker:
    When a sync task is waiting for a txg to complete, we should hurry
    it along by increasing the number of outstanding async writes
    (i.e. make vdev_queue_max_async_writes() return a larger number).
    Initially we might just have a tunable for "minimum async writes
    while a synctask is waiting" and set it to 3.

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2716
This commit is contained in:
Alex Reece 2014-07-18 07:08:31 -08:00 committed by Brian Behlendorf
parent 1f6f97f304
commit acbad6ff67
5 changed files with 46 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/sys/spa.h
View File

@ -822,6 +822,7 @@ extern uint64_t bp_get_dsize(spa_t *spa, const blkptr_t *bp);
extern boolean_t spa_has_slogs(spa_t *spa);
extern boolean_t spa_is_root(spa_t *spa);
extern boolean_t spa_writeable(spa_t *spa);
extern boolean_t spa_has_pending_synctask(spa_t *spa);
extern int spa_mode(spa_t *spa);
extern uint64_t strtonum(const char *str, char **nptr);

3
include/sys/txg.h
View File

@ -23,7 +23,7 @@
* Use is subject to license terms.
*/
/*
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2012, 2014 by Delphix. All rights reserved.
*/
#ifndef _SYS_TXG_H
@ -118,6 +118,7 @@ extern void txg_wait_callbacks(struct dsl_pool *dp);
extern void txg_list_create(txg_list_t *tl, size_t offset);
extern void txg_list_destroy(txg_list_t *tl);
extern boolean_t txg_list_empty(txg_list_t *tl, uint64_t txg);
extern boolean_t txg_all_lists_empty(txg_list_t *tl);
extern boolean_t txg_list_add(txg_list_t *tl, void *p, uint64_t txg);
extern boolean_t txg_list_add_tail(txg_list_t *tl, void *p, uint64_t txg);
extern void *txg_list_remove(txg_list_t *tl, uint64_t txg);

10
module/zfs/spa_misc.c
View File

@ -1756,6 +1756,16 @@ spa_writeable(spa_t *spa)
return (!!(spa->spa_mode & FWRITE));
}
/*
* Returns true if there is a pending sync task in any of the current
* syncing txg, the current quiescing txg, or the current open txg.
*/
boolean_t
spa_has_pending_synctask(spa_t *spa)
{
return (!txg_all_lists_empty(&spa->spa_dsl_pool->dp_sync_tasks));
}
int
spa_mode(spa_t *spa)
{

22
module/zfs/txg.c
View File

@ -21,7 +21,7 @@
/*
* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Portions Copyright 2011 Martin Matuska
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2012, 2014 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
@ -786,6 +786,26 @@ txg_list_empty(txg_list_t *tl, uint64_t txg)
return (tl->tl_head[txg & TXG_MASK] == NULL);
}
/*
* Returns true if all txg lists are empty.
*
* Warning: this is inherently racy (an item could be added immediately
* after this function returns). We don't bother with the lock because
* it wouldn't change the semantics.
*/
boolean_t
txg_all_lists_empty(txg_list_t *tl)
{
int i;
for (i = 0; i < TXG_SIZE; i++) {
if (!txg_list_empty(tl, i)) {
return (B_FALSE);
}
}
return (B_TRUE);
}
/*
* Add an entry to the list (unless it's already on the list).
* Returns B_TRUE if it was actually added.

16
module/zfs/vdev_queue.c
View File

@ -24,7 +24,7 @@
*/
/*
* Copyright (c) 2013 by Delphix. All rights reserved.
* Copyright (c) 2012, 2014 by Delphix. All rights reserved.
*/
#include <sys/zfs_context.h>
@ -230,14 +230,23 @@ vdev_queue_class_min_active(zio_priority_t p)
}
static int
vdev_queue_max_async_writes(uint64_t dirty)
vdev_queue_max_async_writes(spa_t *spa)
{
int writes;
uint64_t dirty = spa->spa_dsl_pool->dp_dirty_total;
uint64_t min_bytes = zfs_dirty_data_max *
zfs_vdev_async_write_active_min_dirty_percent / 100;
uint64_t max_bytes = zfs_dirty_data_max *
zfs_vdev_async_write_active_max_dirty_percent / 100;
/*
* Sync tasks correspond to interactive user actions. To reduce the
* execution time of those actions we push data out as fast as possible.
*/
if (spa_has_pending_synctask(spa)) {
return (zfs_vdev_async_write_max_active);
}
if (dirty < min_bytes)
return (zfs_vdev_async_write_min_active);
if (dirty > max_bytes)
@ -270,8 +279,7 @@ vdev_queue_class_max_active(spa_t *spa, zio_priority_t p)
case ZIO_PRIORITY_ASYNC_READ:
return (zfs_vdev_async_read_max_active);
case ZIO_PRIORITY_ASYNC_WRITE:
return (vdev_queue_max_async_writes(
spa->spa_dsl_pool->dp_dirty_total));
return (vdev_queue_max_async_writes(spa));
case ZIO_PRIORITY_SCRUB:
return (zfs_vdev_scrub_max_active);
default: