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Improve performance of zio_taskq_member

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__zio_execute() calls zio_taskq_member() to determine if we are running
in a zio interrupt taskq, in which case we may need to switch to
processing this zio in a zio issue taskq.  The call to
zio_taskq_member() can become a performance bottleneck when we are
processing a high rate of zio's.

zio_taskq_member() calls taskq_member() on each of the zio interrupt
taskqs, of which there are 21.  This is slow because each call to
taskq_member() does tsd_get(taskq_tsd), which on Linux is relatively
slow.

This commit improves the performance of zio_taskq_member() by having it
cache the value of tsd_get(taskq_tsd), reducing the number of those
calls to 1/21th of the current behavior.

In a test case running `zfs send -c >/dev/null` of a filesystem with
small blocks (average 2.5KB/block), zio_taskq_member() was using 6.7% of
one CPU, and with this change it is reduced to 1.3%.  Overall time to
perform the `zfs send` reduced by 10% (~150,000 block/sec to ~165,000
blocks/sec).

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes #10070
This commit is contained in:
Matthew Ahrens
2020-03-03 10:29:38 -08:00
committed by GitHub
parent 0a0f9a7dc6
commit b3212d2fa6
5 changed files with 24 additions and 2 deletions
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module/zfs/zio.c
+3 -2
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@@ -1865,14 +1865,15 @@ zio_taskq_dispatch(zio_t *zio, zio_taskq_type_t q, boolean_t cutinline)
static boolean_t
zio_taskq_member(zio_t *zio, zio_taskq_type_t q)
{
kthread_t *executor = zio->io_executor;
spa_t *spa = zio->io_spa;
taskq_t *tq = taskq_of_curthread();
for (zio_type_t t = 0; t < ZIO_TYPES; t++) {
spa_taskqs_t *tqs = &spa->spa_zio_taskq[t][q];
uint_t i;
for (i = 0; i < tqs->stqs_count; i++) {
if (taskq_member(tqs->stqs_taskq[i], executor))
if (tqs->stqs_taskq[i] == tq)
return (B_TRUE);
}
}