From: Robin Dong <hao.bigrat@gmail.com>
To: linux-ext4@vger.kernel.org
Cc: Robin Dong <sanbai@taobao.com>
Subject: [PATCH] ext4: check flags's EXT4_GET_BLOCKS_DELALLOC_RESERVE before call ext4_find_delalloc_cluster()
Date: Wed, 7 Dec 2011 14:04:39 +0800 [thread overview]
Message-ID: <1323237879-31800-1-git-send-email-hao.bigrat@gmail.com> (raw)
From: Robin Dong <sanbai@taobao.com>
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_cluster() 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 don't call ext4_find_delalloc_cluster() when use "nodelalloc".
Signed-off-by: Robin Dong <sanbai@taobao.com>
---
fs/ext4/extents.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 61fa9e1..e15d32b 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3724,7 +3724,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
if (!(flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) &&
ext4_ext_in_cache(inode, map->m_lblk, &newex)) {
if (!newex.ee_start_lo && !newex.ee_start_hi) {
- if ((sbi->s_cluster_ratio > 1) &&
+ if ((flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
+ (sbi->s_cluster_ratio > 1) &&
ext4_find_delalloc_cluster(inode, map->m_lblk, 0))
map->m_flags |= EXT4_MAP_FROM_CLUSTER;
@@ -3900,7 +3901,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
}
}
- if ((sbi->s_cluster_ratio > 1) &&
+ if ((flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
+ (sbi->s_cluster_ratio > 1) &&
ext4_find_delalloc_cluster(inode, map->m_lblk, 0))
map->m_flags |= EXT4_MAP_FROM_CLUSTER;
--
1.7.4.1
next reply other threads:[~2011-12-07 6:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-07 6:04 Robin Dong [this message]
2011-12-07 11:02 ` [PATCH] ext4: check flags's EXT4_GET_BLOCKS_DELALLOC_RESERVE before call ext4_find_delalloc_cluster() Yongqiang Yang
2011-12-08 6:59 ` [PATCH v2] ext4: directly leave out of ext4_find_delalloc_range() if filesystem mount with "nodelalloc" Robin Dong
2011-12-08 8:36 ` Yongqiang Yang
2011-12-19 15:39 ` Ted Ts'o
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