Thanks,
Florian
From: Niklas Hambüchen <mail@nh2.me>
Subject: malloc: Fix missing accounting of top chunk in malloc_info [BZ #24026]
Fixes `<total type="rest" size="..."> incorrectly showing as 0 most
of the time.
The rest value being wrong is significant because to compute the
actual amount of memory handed out via malloc, the user must subtract
it from <system type="current" size="...">. That result being wrong
makes investigating memory fragmentation issues like
<https://bugzilla.redhat.com/show_bug.cgi?id=843478> close to
impossible.
2019-08-07 Niklas Hambüchen <mail@nh2.me>
Carlos O'Donell <carlos@redhat.com>
[BZ #24026]
* malloc/malloc.c (__malloc_info): Account for top chunk.
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 343d89f489..0e65d636cd 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5406,6 +5406,12 @@ __malloc_info (int options, FILE *fp)
__libc_lock_lock (ar_ptr->mutex);
+ /* Account for top chunk. The top-most available chunk is
+ treated specially and is never in any bin. See "initial_top"
+ comments. */
+ avail = chunksize (ar_ptr->top);
+ nblocks = 1; /* Top always exists. */
+
for (size_t i = 0; i < NFASTBINS; ++i)
{
mchunkptr p = fastbin (ar_ptr, i);