Avoid arena_prof_accum()-related locking when possible.

Refactor arena_prof_accum() and its callers to avoid arena locking when
prof_interval is 0 (as when profiling is disabled).

Reported by Ben Maurer.

3 files changed, 7 insertions, 35 deletions

diff --git a/src/arena.c b/src/arena.c
index 0c53b07..f9406c7 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -1322,21 +1322,6 @@ arena_bin_malloc_hard(arena_t *arena, arena_bin_t *bin)
 }
 
 void
-arena_prof_accum(arena_t *arena, uint64_t accumbytes)
-{
-
-	cassert(config_prof);
-
-	if (config_prof && prof_interval != 0) {
-		arena->prof_accumbytes += accumbytes;
-		if (arena->prof_accumbytes >= prof_interval) {
-			prof_idump();
-			arena->prof_accumbytes -= prof_interval;
-		}
-	}
-}
-
-void
 arena_tcache_fill_small(arena_t *arena, tcache_bin_t *tbin, size_t binind,
     uint64_t prof_accumbytes)
 {
@@ -1347,11 +1332,8 @@ arena_tcache_fill_small(arena_t *arena, tcache_bin_t *tbin, size_t binind,
 
 	assert(tbin->ncached == 0);
 
-	if (config_prof) {
-		malloc_mutex_lock(&arena->lock);
+	if (config_prof)
 		arena_prof_accum(arena, prof_accumbytes);
-		malloc_mutex_unlock(&arena->lock);
-	}
 	bin = &arena->bins[binind];
 	malloc_mutex_lock(&bin->lock);
 	for (i = 0, nfill = (tcache_bin_info[binind].ncached_max >>
@@ -1459,11 +1441,8 @@ arena_malloc_small(arena_t *arena, size_t size, bool zero)
 		bin->stats.nrequests++;
 	}
 	malloc_mutex_unlock(&bin->lock);
-	if (config_prof && isthreaded == false) {
-		malloc_mutex_lock(&arena->lock);
+	if (config_prof && isthreaded == false)
 		arena_prof_accum(arena, size);
-		malloc_mutex_unlock(&arena->lock);
-	}
 
 	if (zero == false) {
 		if (config_fill) {
@@ -1507,7 +1486,7 @@ arena_malloc_large(arena_t *arena, size_t size, bool zero)
 		arena->stats.lstats[(size >> LG_PAGE) - 1].curruns++;
 	}
 	if (config_prof)
-		arena_prof_accum(arena, size);
+		arena_prof_accum_locked(arena, size);
 	malloc_mutex_unlock(&arena->lock);
 
 	if (zero == false) {
diff --git a/src/prof.c b/src/prof.c
index 04964ef..e21d166 100644
--- a/src/prof.c
+++ b/src/prof.c
@@ -26,7 +26,7 @@ bool		opt_prof_leak = false;
 bool		opt_prof_accum = false;
 char		opt_prof_prefix[PATH_MAX + 1];
 
-uint64_t	prof_interval;
+uint64_t	prof_interval = 0;
 bool		prof_promote;
 
 /*
@@ -1206,13 +1206,11 @@ prof_boot1(void)
 		 */
 		opt_prof = true;
 		opt_prof_gdump = false;
-		prof_interval = 0;
 	} else if (opt_prof) {
 		if (opt_lg_prof_interval >= 0) {
 			prof_interval = (((uint64_t)1U) <<
 			    opt_lg_prof_interval);
-		} else
-			prof_interval = 0;
+		}
 	}
 
 	prof_promote = (opt_prof && opt_lg_prof_sample > LG_PAGE);
diff --git a/src/tcache.c b/src/tcache.c
index 47e14f3..7befdc8 100644
--- a/src/tcache.c
+++ b/src/tcache.c
@@ -97,9 +97,7 @@ tcache_bin_flush_small(tcache_bin_t *tbin, size_t binind, unsigned rem,
 		arena_bin_t *bin = &arena->bins[binind];
 
 		if (config_prof && arena == tcache->arena) {
-			malloc_mutex_lock(&arena->lock);
 			arena_prof_accum(arena, tcache->prof_accumbytes);
-			malloc_mutex_unlock(&arena->lock);
 			tcache->prof_accumbytes = 0;
 		}
 
@@ -180,7 +178,7 @@ tcache_bin_flush_large(tcache_bin_t *tbin, size_t binind, unsigned rem,
 		malloc_mutex_lock(&arena->lock);
 		if ((config_prof || config_stats) && arena == tcache->arena) {
 			if (config_prof) {
-				arena_prof_accum(arena,
+				arena_prof_accum_locked(arena,
 				    tcache->prof_accumbytes);
 				tcache->prof_accumbytes = 0;
 			}
@@ -343,11 +341,8 @@ tcache_destroy(tcache_t *tcache)
 		}
 	}
 
-	if (config_prof && tcache->prof_accumbytes > 0) {
-		malloc_mutex_lock(&tcache->arena->lock);
+	if (config_prof && tcache->prof_accumbytes > 0)
 		arena_prof_accum(tcache->arena, tcache->prof_accumbytes);
-		malloc_mutex_unlock(&tcache->arena->lock);
-	}
 
 	tcache_size = arena_salloc(tcache, false);
 	if (tcache_size <= SMALL_MAXCLASS) {