From: Theodore Ts'o Subject: [PATCH 43/52] percpu_counter: new function percpu_counter_sum_and_set Date: Sat, 5 Jul 2008 13:36:09 -0400 Message-ID: <1215279378-30504-44-git-send-email-tytso@mit.edu> References: <1215279378-30504-1-git-send-email-tytso@mit.edu> <1215279378-30504-2-git-send-email-tytso@mit.edu> <1215279378-30504-3-git-send-email-tytso@mit.edu> <1215279378-30504-4-git-send-email-tytso@mit.edu> <1215279378-30504-5-git-send-email-tytso@mit.edu> <1215279378-30504-6-git-send-email-tytso@mit.edu> <1215279378-30504-7-git-send-email-tytso@mit.edu> <1215279378-30504-8-git-send-email-tytso@mit.edu> <1215279378-30504-9-git-send-email-tytso@mit.edu> <1215279378-30504-10-git-send-email-tytso@mit.edu> <1215279378-30504-11-git-send-email-tytso@mit.edu> <1215279378-30504-12-git-send-email-tytso@mit.edu> <1215279378-30504-13-git-send-email-tytso@mit.edu> <1215279378-30504-14-git-send-email-tytso@mit.edu> <1215279378-30504-15-git-send-email-tytso@mit.edu> <1215279378-30504-16-git-send-email-tytso@mit.edu> <1215279378-30504-17-git-send-email-tytso@mit.edu> <1215279378-30504-18-git-send-email-tytso@mit.edu> <1215279378-30504-19-git-send-email-tytso@mit.edu> <1215279378-30504-20-git-send-email-tytso@mit.edu> <1215279378-30504-21-git-send-email-tytso@mit.edu> <1215279378-30504-22-git-send-email-tytso@mit.edu> <1215279378-30504-23-git-send-email-tytso@mit.edu> <1215279378-30504-24-git-send-email-tytso@mit.edu> <1215279378-30504-25-git-send-email-tytso@mit.edu> <1215279378-30504-26-git-send-email-tytso@mit.edu> <1215279378-30504-27-git-send-email-tytso@mit.edu> <1215279378-30504-28-git-send-email-tytso@mit.edu> <1215279378-30504-29-git-send-email-tytso@mit.edu> <1215279378-30504-30-git-send-email-tytso@mit.edu> <1215279378-30504-31-git-send-email-tytso@mit.edu> <1215279378-30504-32-git-send-email-tytso@mit.edu> <1215279378-30504-33-git-send-email-tytso@mit.edu> <1215279378-30504-34-git-send-email-tytso@mit.edu> <1215279378-30504-35-git-send-email-tytso@mit.edu> <1215279378-30504-36-git-send-email-tytso@mit.edu> <1215279378-30504-37-git-send-email-tytso@mit.edu> <1215279378-30504-38-git-send-email-tytso@mit.edu> <1215279378-30504-39-git-send-email-tytso@mit.edu> <1215279378-30504-40-git-send-email-tytso@mit.edu> <1215279378-30504-41-git-send-email-tytso@mit.edu> <1215279378-30504-42-git-send-email-tytso@mit.edu> <1215279378-30504-43-git-send-email-tytso@mit.edu> Cc: Mingming Cao , "Theodore Ts'o" To: Ext4 Developers List , Linux Kernel Developers List Return-path: Received: from www.church-of-our-saviour.ORG ([69.25.196.31]:33034 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754382AbYGERg3 (ORCPT ); Sat, 5 Jul 2008 13:36:29 -0400 In-Reply-To: <1215279378-30504-43-git-send-email-tytso@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Mingming Cao Delayed allocation need to check free blocks at every write time. percpu_counter_read_positive() is not quit accurate. delayed allocation need a more accurate accounting, but using percpu_counter_sum_positive() is frequently is quite expensive. This patch added a new function to update center counter when sum per-cpu counter, to increase the accurate rate for next percpu_counter_read() and require less calling expensive percpu_counter_sum(). Signed-off-by: Mingming Cao Signed-off-by: "Theodore Ts'o" --- fs/ext4/balloc.c | 2 +- include/linux/percpu_counter.h | 12 +++++++++--- lib/percpu_counter.c | 7 ++++++- 3 files changed, 16 insertions(+), 5 deletions(-) diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 25f63d8..6369bac 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -1621,7 +1621,7 @@ ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi, #ifdef CONFIG_SMP if (free_blocks - root_blocks < FBC_BATCH) free_blocks = - percpu_counter_sum_positive(&sbi->s_freeblocks_counter); + percpu_counter_sum_and_set(&sbi->s_freeblocks_counter); #endif if (free_blocks - root_blocks < nblocks) return free_blocks - root_blocks; diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index 9007ccd..2083888 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -35,7 +35,7 @@ int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount); void percpu_counter_destroy(struct percpu_counter *fbc); void percpu_counter_set(struct percpu_counter *fbc, s64 amount); void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch); -s64 __percpu_counter_sum(struct percpu_counter *fbc); +s64 __percpu_counter_sum(struct percpu_counter *fbc, int set); static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount) { @@ -44,13 +44,19 @@ static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount) static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc) { - s64 ret = __percpu_counter_sum(fbc); + s64 ret = __percpu_counter_sum(fbc, 0); return ret < 0 ? 0 : ret; } +static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc) +{ + return __percpu_counter_sum(fbc, 1); +} + + static inline s64 percpu_counter_sum(struct percpu_counter *fbc) { - return __percpu_counter_sum(fbc); + return __percpu_counter_sum(fbc, 0); } static inline s64 percpu_counter_read(struct percpu_counter *fbc) diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index 1191744..4a8ba4b 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -52,7 +52,7 @@ EXPORT_SYMBOL(__percpu_counter_add); * Add up all the per-cpu counts, return the result. This is a more accurate * but much slower version of percpu_counter_read_positive() */ -s64 __percpu_counter_sum(struct percpu_counter *fbc) +s64 __percpu_counter_sum(struct percpu_counter *fbc, int set) { s64 ret; int cpu; @@ -62,7 +62,12 @@ s64 __percpu_counter_sum(struct percpu_counter *fbc) for_each_online_cpu(cpu) { s32 *pcount = per_cpu_ptr(fbc->counters, cpu); ret += *pcount; + if (set) + *pcount = 0; } + if (set) + fbc->count = ret; + spin_unlock(&fbc->lock); return ret; } -- 1.5.6.rc3.1.g36b7.dirty