[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:
  -----------------
  [root@elm3a241 ~]# ./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 <suparna@in.ibm.com>
Tested-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 0f0b1eadb98dd6dd5f74faa98d8b04012fd0a9f6..84be02e93652bd8e5548d8f07ad6e57c5947c817 100644 (file)
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -925,7 +925,7 @@ int ext3_get_blocks_handle(handle_t *handle, struct inode *inode,
        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 */