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sbitmap: remove swap_lock

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map->swap_lock protects map->cleared from concurrent modification,
however sbitmap_deferred_clear() is already atomically drains it, so
it's guaranteed to not loose bits on concurrent
sbitmap_deferred_clear().

A one threaded tag heavy test on top of nullbk showed ~1.5% t-put
increase, and 3% -> 1% cycle reduction of sbitmap_get() according to perf.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov
2020-11-22 15:35:46 +00:00
committed by Jens Axboe
parent b78beea038
commit 661d4f55a7
2 changed files with 3 additions and 16 deletions
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5
include/linux/sbitmap.h
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@@ -32,11 +32,6 @@ struct sbitmap_word {
* @cleared: word holding cleared bits
*/
unsigned long cleared ____cacheline_aligned_in_smp;
/**
* @swap_lock: Held while swapping word <-> cleared
*/
spinlock_t swap_lock;
} ____cacheline_aligned_in_smp;
/**