Hi.
In btrfs, fdatasync and fsync are identical.
I think fdatasync should skip committing transaction when
inode->i_state is set just I_DIRTY_SYNC and this indicates
only atime or/and mtime updates.
Following patch improves fdatasync throughput.
#sysbench --num-threads=16 --max-requests=10000 --test=fileio
--file-block-size=4K --file-total-size=16G --file-test-mode=rndwr
--file-fsync-mode=fdatasync run
Results:
-2.6.30-rc8
Test execution summary:
total time: 1980.6540s
total number of events: 10001
total time taken by event execution: 1192.9804
per-request statistics:
min: 0.0000s
avg: 0.1193s
max: 15.3720s
approx. 95 percentile: 0.7257s
Threads fairness:
events (avg/stddev): 625.0625/151.32
execution time (avg/stddev): 74.5613/9.46
-2.6.30-rc8-patched
Test execution summary:
total time: 1695.9118s
total number of events: 10000
total time taken by event execution: 871.3214
per-request statistics:
min: 0.0000s
avg: 0.0871s
max: 10.4644s
approx. 95 percentile: 0.4787s
Threads fairness:
events (avg/stddev): 625.0000/131.86
execution time (avg/stddev): 54.4576/8.98
Thanks.
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>
diff -Nrup linux-2.6.30-rc8.org/fs/btrfs/file.c linux-2.6.30-rc8.btrfs/fs/btrfs/file.c
--- linux-2.6.30-rc8.org/fs/btrfs/file.c 2009-06-04 16:26:25.000000000 +0900
+++ linux-2.6.30-rc8.btrfs/fs/btrfs/file.c 2009-06-08 10:48:13.000000000 +0900
@@ -1189,6 +1189,8 @@ int btrfs_sync_file(struct file *file, s
btrfs_wait_ordered_range(inode, 0, (u64)-1);
root->log_batch++;
+ if (datasync && !(inode->i_state & I_DIRTY_PAGES))
+ goto out;
/*
* ok we haven't committed the transaction yet, lets do a commit
*/
--
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