diff options
Diffstat (limited to '0007-malloc-Remove-bin-scanning-from-memalign-bug-30723.patch')
| -rw-r--r-- | 0007-malloc-Remove-bin-scanning-from-memalign-bug-30723.patch | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/0007-malloc-Remove-bin-scanning-from-memalign-bug-30723.patch b/0007-malloc-Remove-bin-scanning-from-memalign-bug-30723.patch new file mode 100644 index 0000000..87db13c --- /dev/null +++ b/0007-malloc-Remove-bin-scanning-from-memalign-bug-30723.patch @@ -0,0 +1,269 @@ +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 07/12] 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 + + 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) + { +-- +2.33.0 + |