Mailing List Archive

Author: phk
Date: 2008-06-09 10:12:31 +0200 (Mon, 09 Jun 2008)
New Revision: 2655

Modified:
trunk/varnish-cache/bin/varnishd/cache_pool.c
Log:
Properly lock n_wrk* statics variables without using more lock operations.

Have the worker threads add themselves to the pool, while the hold the pool
lock anyway.

Collect stats per pool, and have the decimator aggregate over all pools
and into the shared memory counters.


Modified: trunk/varnish-cache/bin/varnishd/cache_pool.c
===================================================================
--- trunk/varnish-cache/bin/varnishd/cache_pool.c 2008-06-08 20:42:28 UTC (rev 2654)
+++ trunk/varnish-cache/bin/varnishd/cache_pool.c 2008-06-09 08:12:31 UTC (rev 2655)
@@ -29,7 +29,6 @@
* $Id$
*
* XXX: automatic thread-pool size adaptation.
- * XXX: unlocked stats variables: consider summing over pools in timer thread.
*/

#include "config.h"
@@ -72,7 +71,8 @@
VTAILQ_HEAD(, workreq) overflow;
unsigned nthr;
unsigned nqueue;
- uintmax_t drops;
+ uintmax_t ndrop;
+ uintmax_t noverflow;
};

static struct wq **wq;
@@ -226,30 +226,33 @@

VSL(SLT_WorkThread, 0, "%p start", w);

+ LOCK(&qp->mtx);
+ qp->nthr++;
while (1) {
CHECK_OBJ_NOTNULL(w, WORKER_MAGIC);
assert(!isnan(w->used));

/* Process overflow requests, if any */
- LOCK(&qp->mtx);
w->wrq = VTAILQ_FIRST(&qp->overflow);
if (w->wrq != NULL) {
VTAILQ_REMOVE(&qp->overflow, w->wrq, list);
qp->nqueue--;
- VSL_stats->n_wrk_queue--; /* XXX: unlocked */
} else {
VTAILQ_INSERT_HEAD(&qp->idle, w, list);
AZ(pthread_cond_wait(&w->cond, &qp->mtx));
}
- UNLOCK(&qp->mtx);
if (w->wrq == NULL)
break;
+ UNLOCK(&qp->mtx);
AN(w->wrq);
wrq = w->wrq;
AN(wrq->func);
wrq->func(w, wrq->priv);
w->wrq = NULL;
+ LOCK(&qp->mtx);
}
+ qp->nthr--;
+ UNLOCK(&qp->mtx);

VSL(SLT_WorkThread, 0, "%p end", w);
if (w->vcl != NULL)
@@ -302,15 +305,13 @@
/* If we have too much in the overflow already, refuse */

if (qp->nqueue > ovfl_max) {
- qp->drops++;
- VSL_stats->n_wrk_drop++; /* XXX: unlocked */
+ qp->ndrop++;
UNLOCK(&qp->mtx);
return (-1);
}

VTAILQ_INSERT_TAIL(&qp->overflow, wrq, list);
- VSL_stats->n_wrk_queue++; /* XXX: unlocked */
- VSL_stats->n_wrk_overflow++; /* XXX: unlocked */
+ qp->noverflow++;
qp->nqueue++;
UNLOCK(&qp->mtx);
AZ(pthread_cond_signal(&herder_cond));
@@ -373,11 +374,11 @@
}

/*--------------------------------------------------------------------
- * If a thread is idle or excess, pick it out of the pool...
+ * If a thread is idle or excess, pick it out of the pool.
*/

static void
-wrk_decimate_flock(struct wq *qp, double t_idle)
+wrk_decimate_flock(struct wq *qp, double t_idle, struct varnish_stats *vs)
{
struct worker *w;

@@ -390,14 +391,16 @@
VTAILQ_REMOVE(&qp->idle, w, list);
else
w = NULL;
+ vs->n_wrk += qp->nthr;
+ vs->n_wrk_queue += qp->nqueue;
+ vs->n_wrk_drop += qp->ndrop;
+ vs->n_wrk_overflow += qp->noverflow;
UNLOCK(&qp->mtx);

/* And give it a kiss on the cheek... */
if (w != NULL) {
AZ(w->wrq);
AZ(pthread_cond_signal(&w->cond));
- qp->nthr--;
- VSL_stats->n_wrk--; /* XXX: unlocked */
(void)usleep(params->wthread_purge_delay * 1000);
}
}
@@ -409,6 +412,7 @@
* Add pools
* Scale constants
* Get rid of excess threads
+ * Aggregate stats across pools
*/

static void *
@@ -416,9 +420,13 @@
{
volatile unsigned u;
double t_idle;
+ struct varnish_stats vsm, *vs;

THR_Name("wrk_herdtimer");

+ memset(&vsm, 0, sizeof vsm);
+ vs = &vsm;
+
(void)priv;
while (1) {
/* Add Pools */
@@ -439,10 +447,20 @@

ovfl_max = (nthr_max * params->overflow_max) / 100;

+ vs->n_wrk = 0;
+ vs->n_wrk_queue = 0;
+ vs->n_wrk_drop = 0;
+ vs->n_wrk_overflow = 0;
+
t_idle = TIM_real() - params->wthread_timeout;
for (u = 0; u < nwq; u++)
- wrk_decimate_flock(wq[u], t_idle);
+ wrk_decimate_flock(wq[u], t_idle, vs);

+ VSL_stats->n_wrk= vs->n_wrk;
+ VSL_stats->n_wrk_queue = vs->n_wrk_queue;
+ VSL_stats->n_wrk_drop = vs->n_wrk_drop;
+ VSL_stats->n_wrk_overflow = vs->n_wrk_overflow;
+
(void)usleep(params->wthread_purge_delay * 1000);
}
}
@@ -470,9 +488,7 @@
VSL_stats->n_wrk_failed++;
(void)usleep(params->wthread_fail_delay * 1000);
} else {
- qp->nthr++;
AZ(pthread_detach(tp));
- VSL_stats->n_wrk++; /* XXX: unlocked */
VSL_stats->n_wrk_create++;
(void)usleep(params->wthread_add_delay * 1000);
}