Evenly distribute the taskq threads across available CPUs

The problem is described in commit aeeb4e0c0ae75b99ebbaa3056f0afc8e12949532.
However, instead of disabling the binding to CPU altogether we just keep the
last CPU index across calls to taskq_create() and thus achieve even
distribution of the taskq threads across all available CPUs.

The implementation based on assumption that task queues initialization
performed in serial manner.

Signed-off-by: Andrey Vesnovaty <andrey.vesnovaty@gmail.com>
Signed-off-by: Andrey Vesnovaty <andreyv@infinidat.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #336

diff --git a/man/man5/spl-module-parameters.5 b/man/man5/spl-module-parameters.5
index 3c134f7757ad349da89dd43591438d7df2020917..9b351762cbc9281e0bba466a8541456489e765f9 100644 (file)
--- a/man/man5/spl-module-parameters.5
+++ b/man/man5/spl-module-parameters.5
@@ -124,3 +124,15 @@ Spin a maximum of N times to acquire lock
 .sp
 .ne -4
 Default value: \fB0\fR.
+.RE
+
+.sp
+.ne 2
+.na
+\fBspl_taskq_thread_bind\fR (int)
+.ad
+.RS 12n
+Bind taskq thread to CPU
+.sp
+Default value: \fB0\fR.
+.RE

diff --git a/module/spl/spl-taskq.c b/module/spl/spl-taskq.c
index 48feb1d220eb12d41d990ab00d9b224d90955eed..0cb2ceeaf15f0818b36ca520e4a75c90318d5300 100644 (file)
--- a/module/spl/spl-taskq.c
+++ b/module/spl/spl-taskq.c
@@ -34,6 +34,10 @@
 
 #define SS_DEBUG_SUBSYS SS_TASKQ
 
+int spl_taskq_thread_bind = 0;
+module_param(spl_taskq_thread_bind, int, 0644);
+MODULE_PARM_DESC(spl_taskq_thread_bind, "Bind taskq thread to CPU by default");
+
 /* Global system-wide dynamic task queue available for all consumers */
 taskq_t *system_taskq;
 EXPORT_SYMBOL(system_taskq);
@@ -781,6 +785,7 @@ taskq_t *
 taskq_create(const char *name, int nthreads, pri_t pri,
     int minalloc, int maxalloc, uint_t flags)
 {
+       static int last_used_cpu = 0;
        taskq_t *tq;
        taskq_thread_t *tqt;
        int rc = 0, i, j = 0;
@@ -843,6 +848,10 @@ taskq_create(const char *name, int nthreads, pri_t pri,
                    "%s/%d", name, i);
                if (tqt->tqt_thread) {
                        list_add(&tqt->tqt_thread_list, &tq->tq_thread_list);
+                       if (spl_taskq_thread_bind) {
+                               last_used_cpu = (last_used_cpu + 1) % num_online_cpus();
+                               kthread_bind(tqt->tqt_thread, last_used_cpu);
+                       }
                        set_user_nice(tqt->tqt_thread, PRIO_TO_NICE(pri));
                        wake_up_process(tqt->tqt_thread);
                        j++;