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Fix dmu_tx_dirty_throttle after arc_c reduction 

After initial arc_c was reduced to arc_c_min it became possible that
on datasets with primarycache=metadata or none dirty data make up most
of ARC capacity and easily more than configured 50% of initial arc_c,
that causes forced txg commits by arc_tempreserve_space() and periodic
very long write delays.

This patch makes arc_tempreserve_space() to use arc_c only after ARC
warmed up once and arc_c really means something, but use arc_c_max
before that.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Matt Macy <mmacy@FreeBSD.org>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored-By: iXsystems, Inc.
Closes #11178
This commit is contained in:
Alexander Motin 2020-11-10 13:39:26 -05:00 committed by Brian Behlendorf
parent b49118220c
commit 050dfc5045
1 changed files with 5 additions and 5 deletions
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10
module/zfs/arc.c
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@ -7070,9 +7070,9 @@ arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg)
*/
uint64_t total_dirty = reserve + arc_tempreserve + anon_size;
uint64_t spa_dirty_anon = spa_dirty_data(spa);
if (total_dirty > arc_c * zfs_arc_dirty_limit_percent / 100 &&
anon_size > arc_c * zfs_arc_anon_limit_percent / 100 &&
uint64_t rarc_c = arc_warm ? arc_c : arc_c_max;
if (total_dirty > rarc_c * zfs_arc_dirty_limit_percent / 100 &&
anon_size > rarc_c * zfs_arc_anon_limit_percent / 100 &&
spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) {
#ifdef ZFS_DEBUG
uint64_t meta_esize = zfs_refcount_count(
@ -7080,9 +7080,9 @@ arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg)
uint64_t data_esize =
zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
"anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
"anon_data=%lluK tempreserve=%lluK rarc_c=%lluK\n",
arc_tempreserve >> 10, meta_esize >> 10,
data_esize >> 10, reserve >> 10, arc_c >> 10);
data_esize >> 10, reserve >> 10, rarc_c >> 10);
#endif
DMU_TX_STAT_BUMP(dmu_tx_dirty_throttle);
return (SET_ERROR(ERESTART));