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xfs: increase the default parallelism levels of pwork clients 

Increase the parallelism level for pwork clients to the workqueue
defaults so that we can take advantage of computers with a lot of CPUs
and a lot of hardware.  On fast systems this will speed up quotacheck by
a large factor, and the following posteof/cowblocks cleanup series will
use the functionality presented in this patch to run garbage collection
as quickly as possible.

We do this by switching the pwork workqueue to unbounded, since the
current user (quotacheck) runs lengthy scans for each work item and we
don't care about dispatching the work on a warm cpu cache or anything
like that.  Also set WQ_SYSFS so that we can monitor where the wq is
running.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
This commit is contained in:
Darrick J. Wong 2021-01-22 16:48:41 -08:00
parent a1a7d05a05
commit f83d436aef
4 changed files with 45 additions and 27 deletions
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38
Documentation/admin-guide/xfs.rst
View File

@ -495,3 +495,41 @@ the class and error context. For example, the default values for
"metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults
to "fail immediately" behaviour. This is done because ENODEV is a fatal,
unrecoverable error no matter how many times the metadata IO is retried.
Workqueue Concurrency
=====================
XFS uses kernel workqueues to parallelize metadata update processes. This
enables it to take advantage of storage hardware that can service many IO
operations simultaneously. This interface exposes internal implementation
details of XFS, and as such is explicitly not part of any userspace API/ABI
guarantee the kernel may give userspace. These are undocumented features of
the generic workqueue implementation XFS uses for concurrency, and they are
provided here purely for diagnostic and tuning purposes and may change at any
time in the future.
The control knobs for a filesystem's workqueues are organized by task at hand
and the short name of the data device. They all can be found in:
/sys/bus/workqueue/devices/${task}!${device}
================ ===========
Task Description
================ ===========
xfs_iwalk-$pid Inode scans of the entire filesystem. Currently limited to
mount time quotacheck.
================ ===========
For example, the knobs for the quotacheck workqueue for /dev/nvme0n1 would be
found in /sys/bus/workqueue/devices/xfs_iwalk-1111!nvme0n1/.
The interesting knobs for XFS workqueues are as follows:
============ ===========
Knob Description
============ ===========
max_active Maximum number of background threads that can be started to
run the work.
cpumask CPUs upon which the threads are allowed to run.
nice Relative priority of scheduling the threads. These are the
same nice levels that can be applied to userspace processes.

5
fs/xfs/xfs_iwalk.c
View File

@ -618,15 +618,12 @@ xfs_iwalk_threaded(
{
struct xfs_pwork_ctl pctl;
xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
unsigned int nr_threads;
int error;
ASSERT(agno < mp->m_sb.sb_agcount);
ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));
nr_threads = xfs_pwork_guess_datadev_parallelism(mp);
error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk",
nr_threads);
error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk");
if (error)
return error;

25
fs/xfs/xfs_pwork.c
View File

@ -61,16 +61,18 @@ xfs_pwork_init(
struct xfs_mount *mp,
struct xfs_pwork_ctl *pctl,
xfs_pwork_work_fn work_fn,
const char *tag,
unsigned int nr_threads)
const char *tag)
{
unsigned int nr_threads = 0;
#ifdef DEBUG
if (xfs_globals.pwork_threads >= 0)
nr_threads = xfs_globals.pwork_threads;
#endif
trace_xfs_pwork_init(mp, nr_threads, current->pid);
pctl->wq = alloc_workqueue("%s-%d", WQ_FREEZABLE, nr_threads, tag,
pctl->wq = alloc_workqueue("%s-%d",
WQ_UNBOUND | WQ_SYSFS | WQ_FREEZABLE, nr_threads, tag,
current->pid);
if (!pctl->wq)
return -ENOMEM;
@ -117,20 +119,3 @@ xfs_pwork_poll(
atomic_read(&pctl->nr_work) == 0, HZ) == 0)
touch_softlockup_watchdog();
}
/*
* Return the amount of parallelism that the data device can handle, or 0 for
* no limit.
*/
unsigned int
xfs_pwork_guess_datadev_parallelism(
struct xfs_mount *mp)
{
struct xfs_buftarg *btp = mp->m_ddev_targp;
/*
* For now we'll go with the most conservative setting possible,
* which is two threads for an SSD and 1 thread everywhere else.
*/
return blk_queue_nonrot(btp->bt_bdev->bd_disk->queue) ? 2 : 1;
}

4
fs/xfs/xfs_pwork.h
View File

@ -51,11 +51,9 @@ xfs_pwork_want_abort(
}
int xfs_pwork_init(struct xfs_mount *mp, struct xfs_pwork_ctl *pctl,
xfs_pwork_work_fn work_fn, const char *tag,
unsigned int nr_threads);
xfs_pwork_work_fn work_fn, const char *tag);
void xfs_pwork_queue(struct xfs_pwork_ctl *pctl, struct xfs_pwork *pwork);
int xfs_pwork_destroy(struct xfs_pwork_ctl *pctl);
void xfs_pwork_poll(struct xfs_pwork_ctl *pctl);
unsigned int xfs_pwork_guess_datadev_parallelism(struct xfs_mount *mp);
#endif /* __XFS_PWORK_H__ */