Make the size of the workerthreads local shmlog workspace a paramter.

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@3176 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_pool.c

@@ -237,7 +237,7 @@ wrk_thread(void *priv)
 {
 	struct worker *w, ww;
 	struct wq *qp;
-	unsigned char wlog[8192]; 	/* XXX: size */
+	unsigned char wlog[params->shm_workspace];
 	struct workreq *wrq;
 
 	THR_SetName("cache-worker");

bin/varnishd/heritage.h

@@ -96,6 +96,7 @@ struct params {
 	/* Memory allocation hints */
 	unsigned		sess_workspace;
 	unsigned		obj_workspace;
+	unsigned		shm_workspace;
 
 	/* Acceptor hints */
 	unsigned		sess_timeout;

bin/varnishd/mgt_param.c

@@ -595,6 +595,15 @@ static const struct parspec parspec[] = {
 		"Minimum is 1024 bytes.",
 		DELAYED_EFFECT,
 		"8192", "bytes" },
+	{ "shm_workspace", tweak_uint, &master.shm_workspace, 4096, UINT_MAX,
+		"Bytes of shmlog workspace allocated for worker threads. "
+		"If too big, it wastes some ram, if too small it causes "
+		"needless flushes of the SHM workspace.\n"
+		"These flushes show up in stats as "
+		"\"SHM flushes due to overflow\".\n"
+		"Minimum is 4096 bytes.",
+		DELAYED_EFFECT,
+		"8192", "bytes" },
 	{ "default_grace", tweak_uint, &master.default_grace, 0, UINT_MAX,
 		"Default grace period.  We will deliver an object "
 		"this long after it has expired, provided another thread "