From: Robin Dong Subject: [PATCH v2] ext4: directly leave out of ext4_find_delalloc_range() if filesystem mount with "nodelalloc" Date: Thu, 8 Dec 2011 14:59:54 +0800 Message-ID: <1323327594-4914-1-git-send-email-hao.bigrat@gmail.com> References: <1323237879-31800-1-git-send-email-hao.bigrat@gmail.com> Cc: Robin Dong To: linux-ext4@vger.kernel.org Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:36219 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750983Ab1LHHAJ (ORCPT ); Thu, 8 Dec 2011 02:00:09 -0500 Received: by iakc1 with SMTP id c1so2133793iak.19 for ; Wed, 07 Dec 2011 23:00:09 -0800 (PST) In-Reply-To: <1323237879-31800-1-git-send-email-hao.bigrat@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Robin Dong We found performance regression when using bigalloc with "nodelalloc" (1MB cluster size): 1. mke2fs -C 1048576 -O ^has_journal,bigalloc /dev/sda 2. mount -o nodelalloc /dev/sda /test/ 3. time dd if=/dev/zero of=/test/io bs=1048576 count=1024 The "dd" will cost about 2 seconds to finish, but if we mke2fs without "bigalloc", "dd" will only cost lesss than 1 second. The reason is: when using ext4 with "nodelalloc", it will call ext4_find_delalloc_cluster() nearly everytime it call ext4_ext_map_blocks(), and ext4_find_delalloc_range() will also scan all pages in cluster because no buffer is "delayed". A cluster has 256 pages (1MB cluster), so it will scan 256 * 256k pags when creating a 1G file. That severely hurts the performance. Therefore, we return out from ext4_find_delalloc_range() when using "nodelalloc". Signed-off-by: Robin Dong --- fs/ext4/extents.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 61fa9e1..60f5f25 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3282,6 +3282,9 @@ static int ext4_find_delalloc_range(struct inode *inode, ext4_lblk_t i, pg_lblk; pgoff_t index; + if (!test_opt(inode->i_sb, DELALLOC)) + return 0; + /* reverse search wont work if fs block size is less than page size */ if (inode->i_blkbits < PAGE_CACHE_SHIFT) search_hint_reverse = 0; -- 1.7.4.1