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| author | brookxu <brookxu.cn@gmail.com> | 2020-08-17 15:36:15 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2020-08-19 12:04:36 -0400 |
| commit | 27bc446e2def38db3244a6eb4bb1d6312936610a (patch) | |
| tree | 567a878460844a91b28ae1a70221f2e3c8e106ee /Documentation | |
| parent | 66d5e0277e225cdc5d272fc22b1aa90a9b0d21ac (diff) | |
| download | linux-27bc446e2def38db3244a6eb4bb1d6312936610a.tar.gz | |
ext4: limit the length of per-inode prealloc list
In the scenario of writing sparse files, the per-inode prealloc list may be very long, resulting in high overhead for ext4_mb_use_preallocated(). To circumvent this problem, we limit the maximum length of per-inode prealloc list to 512 and allow users to modify it. After patching, we observed that the sys ratio of cpu has dropped, and the system throughput has increased significantly. We created a process to write the sparse file, and the running time of the process on the fixed kernel was significantly reduced, as follows: Running time on unfixed kernel： [root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat real 0m2.051s user 0m0.008s sys 0m2.026s Running time on fixed kernel： [root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat real 0m0.471s user 0m0.004s sys 0m0.395s Signed-off-by: Chunguang Xu <brookxu@tencent.com> Link: https://lore.kernel.org/r/d7a98178-056b-6db5-6bce-4ead23f4a257@gmail.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/ext4.rst | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst index 7fc6a72920c9..59bcc4a92602 100644 --- a/Documentation/admin-guide/ext4.rst +++ b/Documentation/admin-guide/ext4.rst @@ -482,6 +482,9 @@ Files in /sys/fs/ext4/<devname>: multiple of this tuning parameter if the stripe size is not set in the ext4 superblock + mb_max_inode_prealloc + The maximum length of per-inode ext4_prealloc_space list. + mb_max_to_scan The maximum number of extents the multiblock allocator will search to find the best extent. |