Messages in this thread | | | Date | Thu, 18 Aug 2022 19:14:14 +0200 | From | David Sterba <> | Subject | Re: [PATCH] fs/btrfs: Use atomic_try_cmpxchg in free_extent_buffer |
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On Tue, Aug 09, 2022 at 06:36:33PM +0200, Uros Bizjak wrote: > Use `atomic_try_cmpxchg(ptr, &old, new)` instead of > `atomic_cmpxchg(ptr, old, new) == old` in free_extent_buffer. This > has two benefits: > > - The x86 cmpxchg instruction returns success in the ZF flag, so this > change saves a compare after cmpxchg, as well as a related move > instruction in the front of cmpxchg. > > - atomic_try_cmpxchg implicitly assigns the *ptr value to &old when > cmpxchg fails, enabling further code simplifications. > > This patch has no functional change. > > Cc: Chris Mason <clm@fb.com> > Cc: Josef Bacik <josef@toxicpanda.com> > Cc: David Sterba <dsterba@suse.com> > Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
It's not in a performance critical code but resulting code is slightly more efficient. Added to misc-next, thanks.
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