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[PATCH v2][BZ #11087] Use atomic operations to track memory
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: libc-alpha at sourceware dot org
- Date: Fri, 18 Oct 2013 10:15:35 +0200
- Subject: [PATCH v2][BZ #11087] Use atomic operations to track memory
- Authentication-results: sourceware.org; auth=none
- References: <20131017114140 dot GA24230 at domone dot podge>
On Thu, Oct 17, 2013 at 01:41:40PM +0200, OndÅej BÃlka wrote:
> Hi,
>
> I fixed this mostly because ulrich was wrong here in several ways.
>
> Calling added locking to update statistics as too expensive is nonsense
> as this is needed only after mmap and mmap + associated minor faults
> are much more costy.
>
> Also there is no locking needed, atomic add will do job well.
>
> This bug affects also malloc_stats.
>
> Comments?
>
Here is version that uses atomic* functions and tracks accurately
maximum. OK to commit?
[BZ #11087]
* malloc/malloc.c: Accurately track mmaped memory.
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 1a18c3f..b814062 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2325,12 +2325,11 @@ static void* sysmalloc(INTERNAL_SIZE_T nb, mstate av)
/* update statistics */
- if (++mp_.n_mmaps > mp_.max_n_mmaps)
- mp_.max_n_mmaps = mp_.n_mmaps;
+ int old = atomic_exchange_and_add (&mp_.n_mmaps, 1);
+ atomic_max (&mp_.max_n_mmaps, old + 1);
- sum = mp_.mmapped_mem += size;
- if (sum > (unsigned long)(mp_.max_mmapped_mem))
- mp_.max_mmapped_mem = sum;
+ sum = atomic_exchange_and_add(&mp_.mmapped_mem, size) + size;
+ atomic_max (&mp_.max_mmapped_mem, sum);
check_chunk(av, p);
@@ -2780,8 +2779,8 @@ munmap_chunk(mchunkptr p)
return;
}
- mp_.n_mmaps--;
- mp_.mmapped_mem -= total_size;
+ atomic_decrement (&mp_.n_mmaps);
+ atomic_add (&mp_.mmapped_mem, -total_size);
/* If munmap failed the process virtual memory address space is in a
bad shape. Just leave the block hanging around, the process will
@@ -2798,6 +2797,7 @@ mremap_chunk(mchunkptr p, size_t new_size)
size_t page_mask = GLRO(dl_pagesize) - 1;
INTERNAL_SIZE_T offset = p->prev_size;
INTERNAL_SIZE_T size = chunksize(p);
+ INTERNAL_SIZE_T old;
char *cp;
assert (chunk_is_mmapped(p));
@@ -2822,10 +2822,8 @@ mremap_chunk(mchunkptr p, size_t new_size)
assert((p->prev_size == offset));
set_head(p, (new_size - offset)|IS_MMAPPED);
- mp_.mmapped_mem -= size + offset;
- mp_.mmapped_mem += new_size;
- if ((unsigned long)mp_.mmapped_mem > (unsigned long)mp_.max_mmapped_mem)
- mp_.max_mmapped_mem = mp_.mmapped_mem;
+ old = atomic_exchange_and_add (&mp_.mmapped_mem, new_size - size - offset);
+ atomic_max (&mp_.max_mmapped_mem, old + new_size - size - offset);
return p;
}