From: Darrick J. Wong <djwong@xxxxxxxxxx>
Increase the default parallelism level for pwork clients so that we can
take advantage of computers with a lot of CPUs and a lot of hardware.
The posteof/cowblocks cleanup series will use the functionality
presented in this patch to constrain the number of background per-ag gc
threads to our best estimate of the amount of parallelism that the
filesystem can sustain.
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
fs/xfs/xfs_iwalk.c | 2 +
fs/xfs/xfs_pwork.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++-----
fs/xfs/xfs_pwork.h | 3 +-
3 files changed, 76 insertions(+), 9 deletions(-)
diff --git a/fs/xfs/xfs_iwalk.c b/fs/xfs/xfs_iwalk.c
index eae3aff9bc97..bb31ef870cdc 100644
--- a/fs/xfs/xfs_iwalk.c
+++ b/fs/xfs/xfs_iwalk.c
@@ -624,7 +624,7 @@ xfs_iwalk_threaded(
ASSERT(agno < mp->m_sb.sb_agcount);
ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));
- nr_threads = xfs_pwork_guess_datadev_parallelism(mp);
+ nr_threads = xfs_pwork_guess_workqueue_threads(mp);
error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk",
nr_threads);
if (error)
diff --git a/fs/xfs/xfs_pwork.c b/fs/xfs/xfs_pwork.c
index b03333f1c84a..53606397ff54 100644
--- a/fs/xfs/xfs_pwork.c
+++ b/fs/xfs/xfs_pwork.c
@@ -118,19 +118,85 @@ xfs_pwork_poll(
touch_softlockup_watchdog();
}
+/* Estimate the amount of parallelism available for a storage device. */
+static unsigned int
+xfs_guess_buftarg_parallelism(
+ struct xfs_buftarg *btp)
+{
+ int iomin;
+ int ioopt;
+
+ /*
+ * The device tells us that it is non-rotational, and we take that to
+ * mean there are no moving parts and that the device can handle all
+ * the CPUs throwing IO requests at it.
+ */
+ if (blk_queue_nonrot(btp->bt_bdev->bd_disk->queue))
+ return num_online_cpus();
+
+ /*
+ * The device has a preferred and minimum IO size that suggest a RAID
+ * setup, so infer the number of disks and assume that the parallelism
+ * is equal to the disk count.
+ */
+ iomin = bdev_io_min(btp->bt_bdev);
+ ioopt = bdev_io_opt(btp->bt_bdev);
+ if (iomin > 0 && ioopt > iomin)
+ return ioopt / iomin;
+
+ /*
+ * The device did not indicate that it has any capabilities beyond that
+ * of a rotating disk with a single drive head, so we estimate no
+ * parallelism at all.
+ */
+ return 1;
+}
+
/*
- * Return the amount of parallelism that the data device can handle, or 0 for
- * no limit.
+ * Estimate the amount of parallelism that is available for metadata operations
+ * on this filesystem.
*/
unsigned int
-xfs_pwork_guess_datadev_parallelism(
+xfs_pwork_guess_metadata_threads(
struct xfs_mount *mp)
{
- struct xfs_buftarg *btp = mp->m_ddev_targp;
+ unsigned int threads;
/*
- * For now we'll go with the most conservative setting possible,
- * which is two threads for an SSD and 1 thread everywhere else.
+ * Estimate the amount of parallelism for metadata operations from the
+ * least capable of the two devices that handle metadata. Cap that
+ * estimate to the number of AGs to avoid unnecessary lock contention.
*/
- return blk_queue_nonrot(btp->bt_bdev->bd_disk->queue) ? 2 : 1;
+ threads = xfs_guess_buftarg_parallelism(mp->m_ddev_targp);
+ if (mp->m_logdev_targp != mp->m_ddev_targp)
+ threads = min(xfs_guess_buftarg_parallelism(mp->m_logdev_targp),
+ threads);
+ threads = min(mp->m_sb.sb_agcount, threads);
+
+ /* If the storage told us it has fancy capabilities, we're done. */
+ if (threads > 1)
+ goto clamp;
+
+ /*
+ * Metadata storage did not even hint that it has any parallel
+ * capability. If the filesystem was formatted with a stripe unit and
+ * width, we'll treat that as evidence of a RAID setup and estimate
+ * the number of disks.
+ */
+ if (mp->m_sb.sb_unit > 0 && mp->m_sb.sb_width > mp->m_sb.sb_unit)
+ threads = mp->m_sb.sb_width / mp->m_sb.sb_unit;
+
+clamp:
+ /* Don't return an estimate larger than the CPU count. */
+ return min(num_online_cpus(), threads);
+}
+
+/* Estimate how many threads we need for a parallel work queue. */
+unsigned int
+xfs_pwork_guess_workqueue_threads(
+ struct xfs_mount *mp)
+{
+ /* pwork queues are not unbounded, so we have to abide WQ_MAX_ACTIVE. */
+ return min_t(unsigned int, xfs_pwork_guess_metadata_threads(mp),
+ WQ_MAX_ACTIVE);
}
diff --git a/fs/xfs/xfs_pwork.h b/fs/xfs/xfs_pwork.h
index 8133124cf3bb..6320bca9c554 100644
--- a/fs/xfs/xfs_pwork.h
+++ b/fs/xfs/xfs_pwork.h
@@ -56,6 +56,7 @@ int xfs_pwork_init(struct xfs_mount *mp, struct xfs_pwork_ctl *pctl,
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);
+unsigned int xfs_pwork_guess_metadata_threads(struct xfs_mount *mp);
+unsigned int xfs_pwork_guess_workqueue_threads(struct xfs_mount *mp);
#endif /* __XFS_PWORK_H__ */
