2006-09-15 16:03:51

by Badari Pulavarty

[permalink] [raw]
Subject: [PATCH] ext3 sequential read regression fix

ext3-get-blocks support caused ~20% degrade in Sequential read
performance (tiobench). Problem is with marking the buffer boundary
so IO can be submitted right away. Here is the patch to fix it.

2.6.18-rc6:
-----------
# ./iotest
1048576+0 records in
1048576+0 records out
4294967296 bytes (4.3 GB) copied, 75.2726 seconds, 57.1 MB/s

real 1m15.285s
user 0m0.276s
sys 0m3.884s


2.6.18-rc6 + fix:
-----------------
[[email protected] ~]# ./iotest
1048576+0 records in
1048576+0 records out
4294967296 bytes (4.3 GB) copied, 62.9356 seconds, 68.2 MB/s


The boundary block check in ext3_get_blocks_handle needs to be adjusted
against the count of blocks mapped in this call, now that it can map
more than one block.

Signed-off-by: Suparna Bhattacharya <[email protected]>
Tested-by: Badari Pulavarty <[email protected]>

linux-2.6.18-rc5-suparna/fs/ext3/inode.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)

diff -puN fs/ext3/inode.c~ext3-multiblock-boundary-fix fs/ext3/inode.c
--- linux-2.6.18-rc5/fs/ext3/inode.c~ext3-multiblock-boundary-fix 2006-09-15 10:53:12.000000000 +0530
+++ linux-2.6.18-rc5-suparna/fs/ext3/inode.c 2006-09-15 10:54:30.000000000 +0530
@@ -925,7 +925,7 @@ int ext3_get_blocks_handle(handle_t *han
set_buffer_new(bh_result);
got_it:
map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
- if (blocks_to_boundary == 0)
+ if (count > blocks_to_boundary)
set_buffer_boundary(bh_result);
err = count;
/* Clean up and exit */