Optimize various per cpu area operations through the new this cpu operations. These operations avoid address calculations through the use of segment prefixes avoid multiple memory references through RMW instructions etc. Reduces code size: Before: christoph@linux-2.6$ size fs/buffer.o text data bss dec hex filename 19169 80 28 19277 4b4d fs/buffer.o After: christoph@linux-2.6$ size fs/buffer.o text data bss dec hex filename 19138 80 28 19246 4b2e fs/buffer.o V3->V4: - Move the use of this_cpu_inc_return into a later patch so that this one can go in without percpu infrastructure changes. Cc: Wu Fengguang Cc: Christoph Hellwig Signed-off-by: Christoph Lameter --- fs/buffer.c | 37 ++++++++++++++++++------------------- 1 file changed, 18 insertions(+), 19 deletions(-) Index: linux-2.6/fs/buffer.c =================================================================== --- linux-2.6.orig/fs/buffer.c 2010-11-30 09:41:30.000000000 -0600 +++ linux-2.6/fs/buffer.c 2010-11-30 09:55:55.000000000 -0600 @@ -1270,12 +1270,10 @@ static inline void check_irqs_on(void) static void bh_lru_install(struct buffer_head *bh) { struct buffer_head *evictee = NULL; - struct bh_lru *lru; check_irqs_on(); bh_lru_lock(); - lru = &__get_cpu_var(bh_lrus); - if (lru->bhs[0] != bh) { + if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { struct buffer_head *bhs[BH_LRU_SIZE]; int in; int out = 0; @@ -1283,7 +1281,8 @@ static void bh_lru_install(struct buffer get_bh(bh); bhs[out++] = bh; for (in = 0; in < BH_LRU_SIZE; in++) { - struct buffer_head *bh2 = lru->bhs[in]; + struct buffer_head *bh2 = + __this_cpu_read(bh_lrus.bhs[in]); if (bh2 == bh) { __brelse(bh2); @@ -1298,7 +1297,7 @@ static void bh_lru_install(struct buffer } while (out < BH_LRU_SIZE) bhs[out++] = NULL; - memcpy(lru->bhs, bhs, sizeof(bhs)); + memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); } bh_lru_unlock(); @@ -1313,23 +1312,22 @@ static struct buffer_head * lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) { struct buffer_head *ret = NULL; - struct bh_lru *lru; unsigned int i; check_irqs_on(); bh_lru_lock(); - lru = &__get_cpu_var(bh_lrus); for (i = 0; i < BH_LRU_SIZE; i++) { - struct buffer_head *bh = lru->bhs[i]; + struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); if (bh && bh->b_bdev == bdev && bh->b_blocknr == block && bh->b_size == size) { if (i) { while (i) { - lru->bhs[i] = lru->bhs[i - 1]; + __this_cpu_write(bh_lrus.bhs[i], + __this_cpu_read(bh_lrus.bhs[i - 1])); i--; } - lru->bhs[0] = bh; + __this_cpu_write(bh_lrus.bhs[0], bh); } get_bh(bh); ret = bh; @@ -3203,22 +3201,23 @@ static void recalc_bh_state(void) int i; int tot = 0; - if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) + if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) return; - __get_cpu_var(bh_accounting).ratelimit = 0; + __this_cpu_write(bh_accounting.ratelimit, 0); for_each_online_cpu(i) tot += per_cpu(bh_accounting, i).nr; buffer_heads_over_limit = (tot > max_buffer_heads); } - + struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) { struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); if (ret) { INIT_LIST_HEAD(&ret->b_assoc_buffers); - get_cpu_var(bh_accounting).nr++; + preempt_disable(); + __this_cpu_inc(bh_accounting.nr); recalc_bh_state(); - put_cpu_var(bh_accounting); + preempt_enable(); } return ret; } @@ -3228,9 +3227,10 @@ void free_buffer_head(struct buffer_head { BUG_ON(!list_empty(&bh->b_assoc_buffers)); kmem_cache_free(bh_cachep, bh); - get_cpu_var(bh_accounting).nr--; + preempt_disable(); + __this_cpu_dec(bh_accounting.nr); recalc_bh_state(); - put_cpu_var(bh_accounting); + preempt_enable(); } EXPORT_SYMBOL(free_buffer_head); @@ -3243,9 +3243,8 @@ static void buffer_exit_cpu(int cpu) brelse(b->bhs[i]); b->bhs[i] = NULL; } - get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr; + this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); per_cpu(bh_accounting, cpu).nr = 0; - put_cpu_var(bh_accounting); } static int buffer_cpu_notify(struct notifier_block *self, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/