lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-08-01 10:06:57 +03:00
Code Activity

malloc: Use branches instead of mtag_granule_mask

Browse Source 
The branches may be better optimized since mtag_enabled is widely used.

Granule size larger than a chunk header is not supported since then we
cannot have both the chunk header and user area granule aligned.  To
fix that for targets with large granule, the chunk layout has to change.

So code that attempted to handle the granule mask generally was changed.
This simplified CHUNK_AVAILABLE_SIZE and the logic in malloc_usable_size.

Reviewed-by: DJ Delorie <dj@redhat.com>
This commit is contained in:
Szabolcs Nagy
2021-02-08 12:39:01 +00:00
parent 9d61722b59
commit 63a20eb03c
2 changed files with 14 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
malloc/arena.c
View File

@ -306,7 +306,6 @@ ptmalloc_init (void)
mtag_enabled = true;
mtag_mmap_flags = __MTAG_MMAP_FLAGS;
mtag_granule_mask = ~(size_t)(__MTAG_GRANULE_SIZE - 1);
}
#endif

34
malloc/malloc.c
View File

@ -442,7 +442,6 @@ void *(*__morecore)(ptrdiff_t) = __default_morecore;
#ifdef USE_MTAG
static bool mtag_enabled = false;
static int mtag_mmap_flags = 0;
static size_t mtag_granule_mask = ~(size_t)0;
#else
# define mtag_enabled false
# define mtag_mmap_flags 0
@ -1333,15 +1332,16 @@ nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
/* Available size of chunk. This is the size of the real usable data
in the chunk, plus the chunk header. */
#ifdef USE_MTAG
#define CHUNK_AVAILABLE_SIZE(p) \
((chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ)) \
& mtag_granule_mask)
#else
#define CHUNK_AVAILABLE_SIZE(p) \
(chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ))
#endif
in the chunk, plus the chunk header. Note: If memory tagging is
enabled the layout changes to accomodate the granule size, this is
wasteful for small allocations so not done by default. The logic
does not work if chunk headers are not granule aligned. */
_Static_assert (__MTAG_GRANULE_SIZE <= CHUNK_HDR_SZ,
"memory tagging is not supported with large granule.");
#define CHUNK_AVAILABLE_SIZE(p) \
(__MTAG_GRANULE_SIZE > SIZE_SZ && __glibc_unlikely (mtag_enabled) ? \
chunksize (p) : \
chunksize (p) + (chunk_is_mmapped (p) ? 0 : SIZE_SZ))
/* Check if REQ overflows when padded and aligned and if the resulting value
is less than PTRDIFF_T. Returns TRUE and the requested size or MINSIZE in
@ -1353,7 +1353,6 @@ checked_request2size (size_t req, size_t *sz) __nonnull (1)
if (__glibc_unlikely (req > PTRDIFF_MAX))
return false;
#ifdef USE_MTAG
/* When using tagged memory, we cannot share the end of the user
block with the header for the next chunk, so ensure that we
allocate blocks that are rounded up to the granule size. Take
@ -1361,8 +1360,9 @@ checked_request2size (size_t req, size_t *sz) __nonnull (1)
number. Ideally, this would be part of request2size(), but that
must be a macro that produces a compile time constant if passed
a constant literal. */
req = (req + ~mtag_granule_mask) & mtag_granule_mask;
#endif
if (__glibc_unlikely (mtag_enabled))
req = (req + (__MTAG_GRANULE_SIZE - 1)) &
~(size_t)(__MTAG_GRANULE_SIZE - 1);
*sz = request2size (req);
return true;
@ -5112,14 +5112,8 @@ musable (void *mem)
result = chunksize (p) - CHUNK_HDR_SZ;
}
else if (inuse (p))
result = chunksize (p) - SIZE_SZ;
result = CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ;
#ifdef USE_MTAG
/* The usable space may be reduced if memory tagging is needed,
since we cannot share the user-space data with malloc's internal
data structure. */
result &= mtag_granule_mask;
#endif
return result;
}
return 0;