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[109.152.100.189]) by smtp.gmail.com with ESMTPSA id q19sm3693742ejz.90.2020.11.22.07.39.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Nov 2020 07:39:06 -0800 (PST) From: Pavel Begunkov To: Jens Axboe , linux-block@vger.kernel.org, Omar Sandoval Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2 1/4] sbitmap: optimise sbitmap_deferred_clear() Date: Sun, 22 Nov 2020 15:35:45 +0000 Message-Id: X-Mailer: git-send-email 2.24.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Because of spinlocks and atomics sbitmap_deferred_clear() have to reload &sb->map[index] on each access even though the map address won't change. Pass in sbitmap_word instead of {sb, index}, so it's cached in a variable. It also improves code generation of sbitmap_find_bit_in_index(). Signed-off-by: Pavel Begunkov --- lib/sbitmap.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 267aa7709416..c1c8a4e69325 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -12,32 +12,32 @@ /* * See if we have deferred clears that we can batch move */ -static inline bool sbitmap_deferred_clear(struct sbitmap *sb, int index) +static inline bool sbitmap_deferred_clear(struct sbitmap_word *map) { unsigned long mask, val; bool ret = false; unsigned long flags; - spin_lock_irqsave(&sb->map[index].swap_lock, flags); + spin_lock_irqsave(&map->swap_lock, flags); - if (!sb->map[index].cleared) + if (!map->cleared) goto out_unlock; /* * First get a stable cleared mask, setting the old mask to 0. */ - mask = xchg(&sb->map[index].cleared, 0); + mask = xchg(&map->cleared, 0); /* * Now clear the masked bits in our free word */ do { - val = sb->map[index].word; - } while (cmpxchg(&sb->map[index].word, val, val & ~mask) != val); + val = map->word; + } while (cmpxchg(&map->word, val, val & ~mask) != val); ret = true; out_unlock: - spin_unlock_irqrestore(&sb->map[index].swap_lock, flags); + spin_unlock_irqrestore(&map->swap_lock, flags); return ret; } @@ -92,7 +92,7 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth) unsigned int i; for (i = 0; i < sb->map_nr; i++) - sbitmap_deferred_clear(sb, i); + sbitmap_deferred_clear(&sb->map[i]); sb->depth = depth; sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word); @@ -139,15 +139,15 @@ static int __sbitmap_get_word(unsigned long *word, unsigned long depth, static int sbitmap_find_bit_in_index(struct sbitmap *sb, int index, unsigned int alloc_hint, bool round_robin) { + struct sbitmap_word *map = &sb->map[index]; int nr; do { - nr = __sbitmap_get_word(&sb->map[index].word, - sb->map[index].depth, alloc_hint, + nr = __sbitmap_get_word(&map->word, map->depth, alloc_hint, !round_robin); if (nr != -1) break; - if (!sbitmap_deferred_clear(sb, index)) + if (!sbitmap_deferred_clear(map)) break; } while (1); @@ -207,7 +207,7 @@ int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint, break; } - if (sbitmap_deferred_clear(sb, index)) + if (sbitmap_deferred_clear(&sb->map[index])) goto again; /* Jump to next index. */ -- 2.24.0