Remove suffix from zio taskq names

For zio taskq's which have multiple instances (e.g. z_rd_int_0,
z_rd_int_1, etc), each one has a unique name (the _0, _1, _2 suffix).
This makes performance analysis more difficult, because by default,
`perf` includes the thread name (which is the same as the taskq name) in
the stack trace.  This means that we get 8 different stacks, all of
which are doing the same thing, but are executed from different taskq's.

We should remove the suffix of the taskq name, so that all the
read-interrupt threads are named z_rd_int.

Note that we already support multiple taskq's with the same name.  This
happens when there are multiple pools.  In this case the taskq has a
different tq_instance, which shows up in /proc/spl/taskq-all.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed by: Richard Elling <[email protected]>
Reviewed-by: Giuseppe Di Natale <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Reviewed by: Pavel Zakharov <[email protected]>
Signed-off-by: Matthew Ahrens <[email protected]>
Closes #7646 

1 files changed, 3 insertions, 8 deletions

diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 45cb6eb00..cdc03e66c 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -923,7 +923,6 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
 	uint_t value = ztip->zti_value;
 	uint_t count = ztip->zti_count;
 	spa_taskqs_t *tqs = &spa->spa_zio_taskq[t][q];
-	char name[32];
 	uint_t flags = 0;
 	boolean_t batch = B_FALSE;
 
@@ -960,14 +959,10 @@ spa_taskqs_init(spa_t *spa, zio_type_t t, zio_taskq_type_t q)
 
 	for (uint_t i = 0; i < count; i++) {
 		taskq_t *tq;
+		char name[32];
 
-		if (count > 1) {
-			(void) snprintf(name, sizeof (name), "%s_%s_%u",
-			    zio_type_name[t], zio_taskq_types[q], i);
-		} else {
-			(void) snprintf(name, sizeof (name), "%s_%s",
-			    zio_type_name[t], zio_taskq_types[q]);
-		}
+		(void) snprintf(name, sizeof (name), "%s_%s",
+		    zio_type_name[t], zio_taskq_types[q]);
 
 		if (zio_taskq_sysdc && spa->spa_proc != &p0) {
 			if (batch)