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Avoid extra taskq_dispatch() calls by DMU

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DMU sync code calls taskq_dispatch() for each sublist of os_dirty_dnodes
and os_synced_dnodes.  Since the number of sublists by default is equal
to number of CPUs, it will dispatch equal, potentially large, number of
tasks, waking up many CPUs to handle them, even if only one or few of
sublists actually have any work to do.

This change adds check for empty sublists to avoid this.

Reviewed by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:  Alexander Motin <mav@FreeBSD.org>
Closes #8909
This commit is contained in:
Alexander Motin 2019-06-25 15:03:38 -04:00 committed by Tony Hutter
parent 05006f125c
commit 04d4df89f4
3 changed files with 38 additions and 5 deletions
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2
include/sys/multilist.h
View File

@ -89,6 +89,8 @@ void multilist_sublist_insert_head(multilist_sublist_t *, void *);
void multilist_sublist_insert_tail(multilist_sublist_t *, void *);
void multilist_sublist_move_forward(multilist_sublist_t *mls, void *obj);
void multilist_sublist_remove(multilist_sublist_t *, void *);
int multilist_sublist_is_empty(multilist_sublist_t *);
int multilist_sublist_is_empty_idx(multilist_t *, unsigned int);
void *multilist_sublist_head(multilist_sublist_t *);
void *multilist_sublist_tail(multilist_sublist_t *);

19
module/zfs/dmu_objset.c
View File

@ -1692,6 +1692,8 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
zio_t *zio;
list_t *list;
dbuf_dirty_record_t *dr;
int num_sublists;
multilist_t *ml;
blkptr_t *blkptr_copy = kmem_alloc(sizeof (*os->os_rootbp), KM_SLEEP);
*blkptr_copy = *os->os_rootbp;
@ -1780,10 +1782,13 @@ dmu_objset_sync(objset_t *os, zio_t *pio, dmu_tx_t *tx)
}
}
for (int i = 0;
i < multilist_get_num_sublists(os->os_dirty_dnodes[txgoff]); i++) {
ml = os->os_dirty_dnodes[txgoff];
num_sublists = multilist_get_num_sublists(ml);
for (int i = 0; i < num_sublists; i++) {
if (multilist_sublist_is_empty_idx(ml, i))
continue;
sync_dnodes_arg_t *sda = kmem_alloc(sizeof (*sda), KM_SLEEP);
sda->sda_list = os->os_dirty_dnodes[txgoff];
sda->sda_list = ml;
sda->sda_sublist_idx = i;
sda->sda_tx = tx;
(void) taskq_dispatch(dmu_objset_pool(os)->dp_sync_taskq,
@ -2086,6 +2091,8 @@ userquota_updates_task(void *arg)
void
dmu_objset_do_userquota_updates(objset_t *os, dmu_tx_t *tx)
{
int num_sublists;
if (!dmu_objset_userused_enabled(os))
return;
@ -2118,8 +2125,10 @@ dmu_objset_do_userquota_updates(objset_t *os, dmu_tx_t *tx)
DMU_OT_USERGROUP_USED, DMU_OT_NONE, 0, tx));
}
for (int i = 0;
i < multilist_get_num_sublists(os->os_synced_dnodes); i++) {
num_sublists = multilist_get_num_sublists(os->os_synced_dnodes);
for (int i = 0; i < num_sublists; i++) {
if (multilist_sublist_is_empty_idx(os->os_synced_dnodes, i))
continue;
userquota_updates_arg_t *uua =
kmem_alloc(sizeof (*uua), KM_SLEEP);
uua->uua_os = os;

22
module/zfs/multilist.c
View File

@ -363,6 +363,28 @@ multilist_sublist_remove(multilist_sublist_t *mls, void *obj)
list_remove(&mls->mls_list, obj);
}
int
multilist_sublist_is_empty(multilist_sublist_t *mls)
{
ASSERT(MUTEX_HELD(&mls->mls_lock));
return (list_is_empty(&mls->mls_list));
}
int
multilist_sublist_is_empty_idx(multilist_t *ml, unsigned int sublist_idx)
{
multilist_sublist_t *mls;
int empty;
ASSERT3U(sublist_idx, <, ml->ml_num_sublists);
mls = &ml->ml_sublists[sublist_idx];
ASSERT(!MUTEX_HELD(&mls->mls_lock));
mutex_enter(&mls->mls_lock);
empty = list_is_empty(&mls->mls_list);
mutex_exit(&mls->mls_lock);
return (empty);
}
void *
multilist_sublist_head(multilist_sublist_t *mls)
{