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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-07-08 16:07:36 +0200 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-07-17 17:14:47 -0700 |
| commit | 04ec006171badc73f749dc1cd9d66e05f8575a81 (patch) | |
| tree | de870dacd5654ddd7a5795a29ccf6de657a519d9 /mm | |
| parent | dcadcf1c30619ead2f3280bfb7f74de8304be2bb (diff) | |
| download | linux-04ec006171badc73f749dc1cd9d66e05f8575a81.tar.gz | |
mm/page_alloc: use try_cmpxchg in set_pfnblock_flags_mask
Use try_cmpxchg instead of cmpxchg in set_pfnblock_flags_mask. x86
CMPXCHG instruction returns success in ZF flag, so this change saves a
compare after cmpxchg (and related move instruction in front of cmpxchg).
The main loop improves from:
1c5d: 48 89 c2 mov %rax,%rdx
1c60: 48 89 c1 mov %rax,%rcx
1c63: 48 21 fa and %rdi,%rdx
1c66: 4c 09 c2 or %r8,%rdx
1c69: f0 48 0f b1 16 lock cmpxchg %rdx,(%rsi)
1c6e: 48 39 c1 cmp %rax,%rcx
1c71: 75 ea jne 1c5d <...>
to:
1c60: 48 89 ca mov %rcx,%rdx
1c63: 48 21 c2 and %rax,%rdx
1c66: 4c 09 c2 or %r8,%rdx
1c69: f0 48 0f b1 16 lock cmpxchg %rdx,(%rsi)
1c6e: 75 f0 jne 1c60 <...>
Link: https://lkml.kernel.org/r/20220708140736.8737-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/page_alloc.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4fa96d3510fe..50d96fff8855 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -602,7 +602,7 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags, { unsigned long *bitmap; unsigned long bitidx, word_bitidx; - unsigned long old_word, word; + unsigned long word; BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4); BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); @@ -618,12 +618,8 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags, flags <<= bitidx; word = READ_ONCE(bitmap[word_bitidx]); - for (;;) { - old_word = cmpxchg(&bitmap[word_bitidx], word, (word & ~mask) | flags); - if (word == old_word) - break; - word = old_word; - } + do { + } while (!try_cmpxchg(&bitmap[word_bitidx], &word, (word & ~mask) | flags)); } void set_pageblock_migratetype(struct page *page, int migratetype) |