[src/trunk]: src/sys/kern Gather sample queue and lock into a static cachelin...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/fce336675478
branches:  trunk
changeset: 337242:fce336675478
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Wed Apr 08 02:49:03 2015 +0000

description:
Gather sample queue and lock into a static cacheline-aligned struct.

diffstat:

 sys/kern/kern_rndq.c |  42 +++++++++++++++++++++---------------------
 1 files changed, 21 insertions(+), 21 deletions(-)

diffs (117 lines):

diff -r 3a6066776815 -r fce336675478 sys/kern/kern_rndq.c
--- a/sys/kern/kern_rndq.c      Wed Apr 08 02:44:07 2015 +0000
+++ b/sys/kern/kern_rndq.c      Wed Apr 08 02:49:03 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_rndq.c,v 1.33 2015/04/08 02:44:07 riastradh Exp $ */
+/*     $NetBSD: kern_rndq.c,v 1.34 2015/04/08 02:49:03 riastradh Exp $ */
 
 /*-
  * Copyright (c) 1997-2013 The NetBSD Foundation, Inc.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.33 2015/04/08 02:44:07 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rndq.c,v 1.34 2015/04/08 02:49:03 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -109,11 +109,13 @@
 } rnd_sample_t;
 
 /*
- * The event queue.  Fields are altered at an interrupt level.
- * All accesses must be protected with the mutex.
+ * The sample queue.  Samples are put into the queue and processed in a
+ * softint in order to limit the latency of adding a sample.
  */
-SIMPLEQ_HEAD(, _rnd_sample_t)  rnd_samples;
-kmutex_t                       rnd_mtx;
+static struct {
+       kmutex_t                        lock;
+       SIMPLEQ_HEAD(, _rnd_sample_t)   q;
+} rnd_samples __cacheline_aligned;
 
 /*
  * Memory pool for sample buffers
@@ -522,7 +524,7 @@
        if (rnd_ready)
                return;
 
-       mutex_init(&rnd_mtx, MUTEX_DEFAULT, IPL_VM);
+       mutex_init(&rnd_samples.lock, MUTEX_DEFAULT, IPL_VM);
        rndsinks_init();
 
        /*
@@ -532,7 +534,7 @@
        c = rnd_counter();
 
        LIST_INIT(&rnd_sources);
-       SIMPLEQ_INIT(&rnd_samples);
+       SIMPLEQ_INIT(&rnd_samples.q);
 
        rndpool_init(&rnd_pool);
        mutex_init(&rndpool_mtx, MUTEX_DEFAULT, IPL_VM);
@@ -738,15 +740,15 @@
         * If there are samples queued up "remove" them from the sample queue
         * by setting the source to the no-collect pseudosource.
         */
-       mutex_spin_enter(&rnd_mtx);
-       sample = SIMPLEQ_FIRST(&rnd_samples);
+       mutex_spin_enter(&rnd_samples.lock);
+       sample = SIMPLEQ_FIRST(&rnd_samples.q);
        while (sample != NULL) {
                if (sample->source == source)
                        sample->source = &rnd_source_no_collect;
 
                sample = SIMPLEQ_NEXT(sample, next);
        }
-       mutex_spin_exit(&rnd_mtx);
+       mutex_spin_exit(&rnd_samples.lock);
 
        if (!cpu_softintr_p()) {        /* XXX XXX very temporary "fix" */
                if (source->state) {
@@ -955,12 +957,12 @@
                return;
        }
 
-       mutex_spin_enter(&rnd_mtx);
+       mutex_spin_enter(&rnd_samples.lock);
        while ((state = SIMPLEQ_FIRST(&tmp_samples))) {
                SIMPLEQ_REMOVE_HEAD(&tmp_samples, next);
-               SIMPLEQ_INSERT_HEAD(&rnd_samples, state, next);
+               SIMPLEQ_INSERT_HEAD(&rnd_samples.q, state, next);
        }
-       mutex_spin_exit(&rnd_mtx);
+       mutex_spin_exit(&rnd_samples.lock);
 
        /* Cause processing of queued samples */
        rnd_schedule_process();
@@ -1040,14 +1042,12 @@
                        SIMPLEQ_HEAD_INITIALIZER(df_samples);
 
        /*
-        * Sample queue is protected by rnd_mtx, drain to onstack queue
-        * and drop lock.
+        * Drain to the on-stack queue and drop the lock.
         */
-
-       mutex_spin_enter(&rnd_mtx);
-       while ((sample = SIMPLEQ_FIRST(&rnd_samples))) {
+       mutex_spin_enter(&rnd_samples.lock);
+       while ((sample = SIMPLEQ_FIRST(&rnd_samples.q))) {
                found++;
-               SIMPLEQ_REMOVE_HEAD(&rnd_samples, next);
+               SIMPLEQ_REMOVE_HEAD(&rnd_samples.q, next);
                /*
                 * We repeat this check here, since it is possible
                 * the source was disabled before we were called, but
@@ -1061,7 +1061,7 @@
                        SIMPLEQ_INSERT_TAIL(&dq_samples, sample, next);
                }
        }
-       mutex_spin_exit(&rnd_mtx);
+       mutex_spin_exit(&rnd_samples.lock);
 
        /* Don't thrash the rndpool mtx either.  Hold, add all samples. */
        mutex_spin_enter(&rndpool_mtx);