From a8118233ec0369e00629fe853a5655c0dabf83d2 Mon Sep 17 00:00:00 2001
From: Jason Evans <je@fb.com>
Date: Mon, 14 Mar 2011 12:56:51 -0700
Subject: [PATCH] Fix a thread cache stats merging bug.

When a thread cache flushes objects to their arenas due to an abundance
of cached objects, it merges the allocation request count for the
associated size class, and increments a flush counter.  If none of the
flushed objects came from the thread's assigned arena, then the merging
wouldn't happen (though the counter would typically eventually be
merged), nor would the flush counter be incremented (a hard bug).  Fix
this via extra conditional code just after the flush loop.
---
 jemalloc/src/tcache.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/jemalloc/src/tcache.c b/jemalloc/src/tcache.c
index cbbe7a11..e9b067d4 100644
--- a/jemalloc/src/tcache.c
+++ b/jemalloc/src/tcache.c
@@ -58,6 +58,9 @@ tcache_bin_flush_small(tcache_bin_t *tbin, size_t binind, unsigned rem
 	void *flush, *deferred, *ptr;
 	unsigned i, nflush, ndeferred;
 	bool first_pass;
+#ifdef JEMALLOC_STATS
+	bool merged_stats = false;
+#endif
 
 	assert(binind < nbins);
 	assert(rem <= tbin->ncached);
@@ -82,6 +85,8 @@ tcache_bin_flush_small(tcache_bin_t *tbin, size_t binind, unsigned rem
 		malloc_mutex_lock(&bin->lock);
 #ifdef JEMALLOC_STATS
 		if (arena == tcache->arena) {
+			assert(merged_stats == false);
+			merged_stats = true;
 			bin->stats.nflushes++;
 			bin->stats.nrequests += tbin->tstats.nrequests;
 			tbin->tstats.nrequests = 0;
@@ -119,6 +124,20 @@ tcache_bin_flush_small(tcache_bin_t *tbin, size_t binind, unsigned rem
 			first_pass = false;
 		}
 	}
+#ifdef JEMALLOC_STATS
+	if (merged_stats == false) {
+		/*
+		 * The flush loop didn't happen to flush to this thread's
+		 * arena, so the stats didn't get merged.  Manually do so now.
+		 */
+		arena_bin_t *bin = &tcache->arena->bins[binind];
+		malloc_mutex_lock(&bin->lock);
+		bin->stats.nflushes++;
+		bin->stats.nrequests += tbin->tstats.nrequests;
+		tbin->tstats.nrequests = 0;
+		malloc_mutex_unlock(&bin->lock);
+	}
+#endif
 
 	tbin->ncached = rem;
 	if (tbin->ncached < tbin->low_water)