From 7ef5e54e2e28884a04dc800657967b891239e933 Mon Sep 17 00:00:00 2001 From: Adam Leventhal Date: Mon, 6 May 2013 12:24:30 -0700 Subject: Illumos #3581 spa_zio_taskq[ZIO_TYPE_FREE][ZIO_TASKQ_ISSUE]->tq_lock contention 3581 spa_zio_taskq[ZIO_TYPE_FREE][ZIO_TASKQ_ISSUE]->tq_lock is piping hot Reviewed by: Matthew Ahrens Reviewed by: George Wilson Reviewed by: Christopher Siden Reviewed by: Gordon Ross Approved by: Richard Lowe References: illumos/illumos-gate@ec94d32 https://illumos.org/issues/3581 Notes for Linux port: Earlier commit 08d08eb reduced contention on this taskq lock by simply reducing the number of z_fr_iss threads from 100 to one-per-CPU. We also optimized the taskq implementation in zfsonlinux/spl@3c6ed54. These changes significantly improved unlink performance to acceptable levels. This patch further reduces time spent spinning on this lock by randomly dispatching the work items over multiple independent task queues. The Illumos ZFS developers stated that this lock contention only arose after "3329 spa_sync() spends 10-20% of its time in spa_free_sync_cb()" was landed. It's not clear if 3329 affects the Linux port or not. I didn't see spa_free_sync_cb() show up in oprofile sessions while unlinking large files, but I may just not have used the right test case. I tested unlinking a 1 TB of data with and without the patch and didn't observe a meaningful difference in elapsed time. However, oprofile showed that the percent time spent in taskq_thread() was reduced from about 16% to about 5%. Aside from a possible slight performance benefit this may be worth landing if only for the sake of maintaining consistency with upstream. Ported-by: Ned Bass Closes #1327 --- include/sys/spa_impl.h | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'include/sys') diff --git a/include/sys/spa_impl.h b/include/sys/spa_impl.h index 5bd0e0a9c..1b12b4e3a 100644 --- a/include/sys/spa_impl.h +++ b/include/sys/spa_impl.h @@ -80,16 +80,16 @@ typedef struct spa_config_dirent { char *scd_path; } spa_config_dirent_t; -enum zio_taskq_type { +typedef enum zio_taskq_type { ZIO_TASKQ_ISSUE = 0, ZIO_TASKQ_ISSUE_HIGH, ZIO_TASKQ_INTERRUPT, ZIO_TASKQ_INTERRUPT_HIGH, ZIO_TASKQ_TYPES -}; +} zio_taskq_type_t; /* - * State machine for the zpool-pooname process. The states transitions + * State machine for the zpool-poolname process. The states transitions * are done as follows: * * From To Routine @@ -107,6 +107,11 @@ typedef enum spa_proc_state { SPA_PROC_GONE /* spa_thread() is exiting, spa_proc = &p0 */ } spa_proc_state_t; +typedef struct spa_taskqs { + uint_t stqs_count; + taskq_t **stqs_taskq; +} spa_taskqs_t; + struct spa { /* * Fields protected by spa_namespace_lock. @@ -125,7 +130,7 @@ struct spa { uint8_t spa_sync_on; /* sync threads are running */ spa_load_state_t spa_load_state; /* current load operation */ uint64_t spa_import_flags; /* import specific flags */ - taskq_t *spa_zio_taskq[ZIO_TYPES][ZIO_TASKQ_TYPES]; + spa_taskqs_t spa_zio_taskq[ZIO_TYPES][ZIO_TASKQ_TYPES]; dsl_pool_t *spa_dsl_pool; boolean_t spa_is_initializing; /* true while opening pool */ metaslab_class_t *spa_normal_class; /* normal data class */ @@ -243,6 +248,9 @@ struct spa { extern char *spa_config_path; +extern void spa_taskq_dispatch_ent(spa_t *spa, zio_type_t t, zio_taskq_type_t q, + task_func_t *func, void *arg, uint_t flags, taskq_ent_t *ent); + #ifdef __cplusplus } #endif -- cgit v1.2.3