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authorJens Axboe <jens.axboe@oracle.com>2009-02-17 13:59:08 +0100
committerGreg Kroah-Hartman <gregkh@suse.de>2009-05-02 10:24:38 -0700
commitca66c0da0992f6bc96c80d10b446b57849669663 (patch)
tree89999c997221b48aea852eb629f42a5406fd07f4
parente2627e220fe64f2a7e501b512719e7b7be73466b (diff)
downloadlwn-ca66c0da0992f6bc96c80d10b446b57849669663.tar.gz
lwn-ca66c0da0992f6bc96c80d10b446b57849669663.zip
block: revert part of 18ce3751ccd488c78d3827e9f6bf54e6322676fb
commit 78f707bfc723552e8309b7c38a8d0cc51012e813 upstream. The above commit added WRITE_SYNC and switched various places to using that for committing writes that will be waited upon immediately after submission. However, this causes a performance regression with AS and CFQ for ext3 at least, since sync_dirty_buffer() will submit some writes with WRITE_SYNC while ext3 has sumitted others dependent writes without the sync flag set. This causes excessive anticipation/idling in the IO scheduler because sync and async writes get interleaved, causing a big performance regression for the below test case (which is meant to simulate sqlite like behaviour). ---- test case ---- int main(int argc, char **argv) { int fdes, i; FILE *fp; struct timeval start; struct timeval end; struct timeval res; gettimeofday(&start, NULL); for (i=0; i<ROWS; i++) { fp = fopen("test_file", "a"); fprintf(fp, "Some Text Data\n"); fdes = fileno(fp); fsync(fdes); fclose(fp); } gettimeofday(&end, NULL); timersub(&end, &start, &res); fprintf(stdout, "time to write %d lines is %ld(msec)\n", ROWS, (res.tv_sec*1000000 + res.tv_usec)/1000); return 0; } ------------------- Thanks to Sean.White@APCC.com for tracking down this performance regression and providing a test case. Signed-off-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--fs/buffer.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index a542f970737e..a5d806dfb143 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3042,7 +3042,7 @@ int sync_dirty_buffer(struct buffer_head *bh)
if (test_clear_buffer_dirty(bh)) {
get_bh(bh);
bh->b_end_io = end_buffer_write_sync;
- ret = submit_bh(WRITE_SYNC, bh);
+ ret = submit_bh(WRITE, bh);
wait_on_buffer(bh);
if (buffer_eopnotsupp(bh)) {
clear_buffer_eopnotsupp(bh);