From: Tao Ma Subject: [PATCH] ext4: speed up group trim with the right free block count. Date: Fri, 21 Jan 2011 10:32:11 +0800 Message-ID: <1295577131-3778-1-git-send-email-tm@tao.ma> Cc: "Theodore Ts'o" To: linux-ext4@vger.kernel.org Return-path: Received: from oproxy1-pub.bluehost.com ([66.147.249.253]:37325 "HELO oproxy1-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752201Ab1AUCcc (ORCPT ); Thu, 20 Jan 2011 21:32:32 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Tao Ma When we trim some free blocks in a group of ext4, we should calculate the free blocks properly and check whether there are enough freed blocks left for us to trim. Current solution will only calculate free spaces if they are large for a trim which isn't appropriate. Let us see a small example: a group has 1.5M free which are 300k, 300k, 300k, 300k, 300k. And minblocks is 1M. With current solution, we have to iterate the whole group since these 300k will never be subtracted from 1.5M. But actually we should exit after we find the first 2 free spaces since the left 3 chunks only sum up to 900K if we subtract the first 600K although they can't be trimed. Cc: "Theodore Ts'o" Signed-off-by: Tao Ma --- fs/ext4/mballoc.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 851f49b..970e471 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4737,7 +4737,7 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b, ext4_grpblk_t start, ext4_grpblk_t max, ext4_grpblk_t minblocks) { void *bitmap; - ext4_grpblk_t next, count = 0; + ext4_grpblk_t next, count = 0, free_count = 0; ext4_group_t group; int ret = 0; @@ -4762,6 +4762,7 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b, break; count += next - start; } + free_count += next - start; start = next + 1; if (fatal_signal_pending(current)) { @@ -4775,7 +4776,7 @@ ext4_grpblk_t ext4_trim_all_free(struct super_block *sb, struct ext4_buddy *e4b, ext4_lock_group(sb, group); } - if ((e4b->bd_info->bb_free - count) < minblocks) + if ((e4b->bd_info->bb_free - free_count) < minblocks) break; } ext4_unlock_group(sb, group); -- 1.6.3.GIT