From f1646c728fa8e754ae60ee1b155c4b0b24e2271c Mon Sep 17 00:00:00 2001 From: Matthew Ahrens Date: Tue, 3 Mar 2020 10:29:38 -0800 Subject: [PATCH] Improve performance of zio_taskq_member __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 Reviewed-by: Serapheim Dimitropoulos Reviewed-by: Ryan Moeller Reviewed-by: Tony Nguyen Signed-off-by: Matthew Ahrens Closes #10070 --- include/spl/sys/taskq.h | 1 + include/sys/zfs_context.h | 1 + lib/libzpool/taskq.c | 12 ++++++++++++ module/spl/spl-taskq.c | 7 +++++++ module/zfs/zio.c | 5 +++-- 5 files changed, 24 insertions(+), 2 deletions(-) diff --git a/include/spl/sys/taskq.h b/include/spl/sys/taskq.h index 7353367a2102..7a1ee9ec4f1b 100644 --- a/include/spl/sys/taskq.h +++ b/include/spl/sys/taskq.h @@ -151,6 +151,7 @@ extern void taskq_wait_outstanding(taskq_t *, taskqid_t); extern void taskq_wait(taskq_t *); extern int taskq_cancel_id(taskq_t *, taskqid_t); extern int taskq_member(taskq_t *, kthread_t *); +extern taskq_t *taskq_of_curthread(void); #define taskq_create_proc(name, nthreads, pri, min, max, proc, flags) \ taskq_create(name, nthreads, pri, min, max, flags) diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h index def9de781460..7566f74d49d1 100644 --- a/include/sys/zfs_context.h +++ b/include/sys/zfs_context.h @@ -499,6 +499,7 @@ extern void taskq_wait(taskq_t *); extern void taskq_wait_id(taskq_t *, taskqid_t); extern void taskq_wait_outstanding(taskq_t *, taskqid_t); extern int taskq_member(taskq_t *, kthread_t *); +extern taskq_t *taskq_of_curthread(void); extern int taskq_cancel_id(taskq_t *, taskqid_t); extern void system_taskq_init(void); extern void system_taskq_fini(void); diff --git a/lib/libzpool/taskq.c b/lib/libzpool/taskq.c index ae67906fe008..456080f7f247 100644 --- a/lib/libzpool/taskq.c +++ b/lib/libzpool/taskq.c @@ -34,6 +34,8 @@ int taskq_now; taskq_t *system_taskq; taskq_t *system_delay_taskq; +static pthread_key_t taskq_tsd; + #define TASKQ_ACTIVE 0x00010000 static taskq_ent_t * @@ -213,6 +215,8 @@ taskq_thread(void *arg) taskq_ent_t *t; boolean_t prealloc; + VERIFY0(pthread_setspecific(taskq_tsd, tq)); + mutex_enter(&tq->tq_lock); while (tq->tq_flags & TASKQ_ACTIVE) { if ((t = tq->tq_task.tqent_next) == &tq->tq_task) { @@ -343,6 +347,12 @@ taskq_member(taskq_t *tq, kthread_t *t) return (0); } +taskq_t * +taskq_of_curthread(void) +{ + return (pthread_getspecific(taskq_tsd)); +} + int taskq_cancel_id(taskq_t *tq, taskqid_t id) { @@ -352,6 +362,7 @@ taskq_cancel_id(taskq_t *tq, taskqid_t id) void system_taskq_init(void) { + VERIFY0(pthread_key_create(&taskq_tsd, NULL)); system_taskq = taskq_create("system_taskq", 64, maxclsyspri, 4, 512, TASKQ_DYNAMIC | TASKQ_PREPOPULATE); system_delay_taskq = taskq_create("delay_taskq", 4, maxclsyspri, 4, @@ -365,4 +376,5 @@ system_taskq_fini(void) system_taskq = NULL; /* defensive */ taskq_destroy(system_delay_taskq); system_delay_taskq = NULL; + VERIFY0(pthread_key_delete(taskq_tsd)); } diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c index a65c95615db0..8070ee9a1ad5 100644 --- a/module/spl/spl-taskq.c +++ b/module/spl/spl-taskq.c @@ -488,6 +488,13 @@ taskq_member(taskq_t *tq, kthread_t *t) } EXPORT_SYMBOL(taskq_member); +taskq_t * +taskq_of_curthread(void) +{ + return (tsd_get(taskq_tsd)); +} +EXPORT_SYMBOL(taskq_of_curthread); + /* * Cancel an already dispatched task given the task id. Still pending tasks * will be immediately canceled, and if the task is active the function will diff --git a/module/zfs/zio.c b/module/zfs/zio.c index 1bd9f2e90b0a..0526dbc52270 100644 --- a/module/zfs/zio.c +++ b/module/zfs/zio.c @@ -1803,14 +1803,15 @@ 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); } }