+++ /dev/null
-From 2af141bda3cd407abd4bedf615f9e45fe79518e2 Mon Sep 17 00:00:00 2001
-From: Florian Weimer <fweimer@redhat.com>
-Date: Thu, 10 Aug 2023 19:36:56 +0200
-Subject: [PATCH 08/44] malloc: Remove bin scanning from memalign (bug 30723)
-
-On the test workload (mpv --cache=yes with VP9 video decoding), the
-bin scanning has a very poor success rate (less than 2%). The tcache
-scanning has about 50% success rate, so keep that.
-
-Update comments in malloc/tst-memalign-2 to indicate the purpose
-of the tests. Even with the scanning removed, the additional
-merging opportunities since commit 542b1105852568c3ebc712225ae78b
-("malloc: Enable merging of remainders in memalign (bug 30723)")
-are sufficient to pass the existing large bins test.
-
-Remove leftover variables from _int_free from refactoring in the
-same commit.
-
-Reviewed-by: DJ Delorie <dj@redhat.com>
-(cherry picked from commit 0dc7fc1cf094406a138e4d1bcf9553e59edcf89d)
----
- NEWS | 1 +
- malloc/malloc.c | 169 ++--------------------------------------
- malloc/tst-memalign-2.c | 7 +-
- 3 files changed, 11 insertions(+), 166 deletions(-)
-
-diff --git a/NEWS b/NEWS
-index 872bc8907b..c339cb444e 100644
---- a/NEWS
-+++ b/NEWS
-@@ -132,6 +132,7 @@ The following bugs are resolved with this release:
- [30555] string: strerror can incorrectly return NULL
- [30579] malloc: trim_threshold in realloc lead to high memory usage
- [30662] nscd: Group and password cache use errno in place of errval
-+ [30723] posix_memalign repeatedly scans long bin lists
- \f
- Version 2.37
-
-diff --git a/malloc/malloc.c b/malloc/malloc.c
-index 948f9759af..d0bbbf3710 100644
---- a/malloc/malloc.c
-+++ b/malloc/malloc.c
-@@ -4488,12 +4488,6 @@ _int_free (mstate av, mchunkptr p, int have_lock)
- {
- INTERNAL_SIZE_T size; /* its size */
- mfastbinptr *fb; /* associated fastbin */
-- mchunkptr nextchunk; /* next contiguous chunk */
-- INTERNAL_SIZE_T nextsize; /* its size */
-- int nextinuse; /* true if nextchunk is used */
-- INTERNAL_SIZE_T prevsize; /* size of previous contiguous chunk */
-- mchunkptr bck; /* misc temp for linking */
-- mchunkptr fwd; /* misc temp for linking */
-
- size = chunksize (p);
-
-@@ -5032,42 +5026,6 @@ _int_realloc (mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
- ------------------------------ memalign ------------------------------
- */
-
--/* Returns 0 if the chunk is not and does not contain the requested
-- aligned sub-chunk, else returns the amount of "waste" from
-- trimming. NB is the *chunk* byte size, not the user byte
-- size. */
--static size_t
--chunk_ok_for_memalign (mchunkptr p, size_t alignment, size_t nb)
--{
-- void *m = chunk2mem (p);
-- INTERNAL_SIZE_T size = chunksize (p);
-- void *aligned_m = m;
--
-- if (__glibc_unlikely (misaligned_chunk (p)))
-- malloc_printerr ("_int_memalign(): unaligned chunk detected");
--
-- aligned_m = PTR_ALIGN_UP (m, alignment);
--
-- INTERNAL_SIZE_T front_extra = (intptr_t) aligned_m - (intptr_t) m;
--
-- /* We can't trim off the front as it's too small. */
-- if (front_extra > 0 && front_extra < MINSIZE)
-- return 0;
--
-- /* If it's a perfect fit, it's an exception to the return value rule
-- (we would return zero waste, which looks like "not usable"), so
-- handle it here by returning a small non-zero value instead. */
-- if (size == nb && front_extra == 0)
-- return 1;
--
-- /* If the block we need fits in the chunk, calculate total waste. */
-- if (size > nb + front_extra)
-- return size - nb;
--
-- /* Can't use this chunk. */
-- return 0;
--}
--
- /* BYTES is user requested bytes, not requested chunksize bytes. */
- static void *
- _int_memalign (mstate av, size_t alignment, size_t bytes)
-@@ -5082,7 +5040,6 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
- mchunkptr remainder; /* spare room at end to split off */
- unsigned long remainder_size; /* its size */
- INTERNAL_SIZE_T size;
-- mchunkptr victim;
-
- nb = checked_request2size (bytes);
- if (nb == 0)
-@@ -5101,129 +5058,13 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
- we don't find anything in those bins, the common malloc code will
- scan starting at 2x. */
-
-- /* This will be set if we found a candidate chunk. */
-- victim = NULL;
--
-- /* Fast bins are singly-linked, hard to remove a chunk from the middle
-- and unlikely to meet our alignment requirements. We have not done
-- any experimentation with searching for aligned fastbins. */
--
-- if (av != NULL)
-- {
-- int first_bin_index;
-- int first_largebin_index;
-- int last_bin_index;
--
-- if (in_smallbin_range (nb))
-- first_bin_index = smallbin_index (nb);
-- else
-- first_bin_index = largebin_index (nb);
--
-- if (in_smallbin_range (nb * 2))
-- last_bin_index = smallbin_index (nb * 2);
-- else
-- last_bin_index = largebin_index (nb * 2);
--
-- first_largebin_index = largebin_index (MIN_LARGE_SIZE);
--
-- int victim_index; /* its bin index */
--
-- for (victim_index = first_bin_index;
-- victim_index < last_bin_index;
-- victim_index ++)
-- {
-- victim = NULL;
--
-- if (victim_index < first_largebin_index)
-- {
-- /* Check small bins. Small bin chunks are doubly-linked despite
-- being the same size. */
--
-- mchunkptr fwd; /* misc temp for linking */
-- mchunkptr bck; /* misc temp for linking */
--
-- bck = bin_at (av, victim_index);
-- fwd = bck->fd;
-- while (fwd != bck)
-- {
-- if (chunk_ok_for_memalign (fwd, alignment, nb) > 0)
-- {
-- victim = fwd;
--
-- /* Unlink it */
-- victim->fd->bk = victim->bk;
-- victim->bk->fd = victim->fd;
-- break;
-- }
--
-- fwd = fwd->fd;
-- }
-- }
-- else
-- {
-- /* Check large bins. */
-- mchunkptr fwd; /* misc temp for linking */
-- mchunkptr bck; /* misc temp for linking */
-- mchunkptr best = NULL;
-- size_t best_size = 0;
--
-- bck = bin_at (av, victim_index);
-- fwd = bck->fd;
-+ /* Call malloc with worst case padding to hit alignment. */
-+ m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
-
-- while (fwd != bck)
-- {
-- int extra;
--
-- if (chunksize (fwd) < nb)
-- break;
-- extra = chunk_ok_for_memalign (fwd, alignment, nb);
-- if (extra > 0
-- && (extra <= best_size || best == NULL))
-- {
-- best = fwd;
-- best_size = extra;
-- }
-+ if (m == 0)
-+ return 0; /* propagate failure */
-
-- fwd = fwd->fd;
-- }
-- victim = best;
--
-- if (victim != NULL)
-- {
-- unlink_chunk (av, victim);
-- break;
-- }
-- }
--
-- if (victim != NULL)
-- break;
-- }
-- }
--
-- /* Strategy: find a spot within that chunk that meets the alignment
-- request, and then possibly free the leading and trailing space.
-- This strategy is incredibly costly and can lead to external
-- fragmentation if header and footer chunks are unused. */
--
-- if (victim != NULL)
-- {
-- p = victim;
-- m = chunk2mem (p);
-- set_inuse (p);
-- if (av != &main_arena)
-- set_non_main_arena (p);
-- }
-- else
-- {
-- /* Call malloc with worst case padding to hit alignment. */
--
-- m = (char *) (_int_malloc (av, nb + alignment + MINSIZE));
--
-- if (m == 0)
-- return 0; /* propagate failure */
--
-- p = mem2chunk (m);
-- }
-+ p = mem2chunk (m);
-
- if ((((unsigned long) (m)) % alignment) != 0) /* misaligned */
- {
-diff --git a/malloc/tst-memalign-2.c b/malloc/tst-memalign-2.c
-index f229283dbf..ecd6fa249e 100644
---- a/malloc/tst-memalign-2.c
-+++ b/malloc/tst-memalign-2.c
-@@ -86,7 +86,8 @@ do_test (void)
- TEST_VERIFY (tcache_allocs[i].ptr1 == tcache_allocs[i].ptr2);
- }
-
-- /* Test for non-head tcache hits. */
-+ /* Test for non-head tcache hits. This exercises the memalign
-+ scanning code to find matching allocations. */
- for (i = 0; i < array_length (ptr); ++ i)
- {
- if (i == 4)
-@@ -113,7 +114,9 @@ do_test (void)
- free (p);
- TEST_VERIFY (count > 0);
-
-- /* Large bins test. */
-+ /* Large bins test. This verifies that the over-allocated parts
-+ that memalign releases for future allocations can be reused by
-+ memalign itself at least in some cases. */
-
- for (i = 0; i < LN; ++ i)
- {
---
-2.39.2
-
projects / ipfire-2.x.git / blobdiff