From: Hisashi Hifumi Date: Wed, 10 Jun 2009 15:13:17 +0000 (-0400) Subject: Btrfs: fdatasync should skip metadata writeout X-Git-Tag: v2.6.31-rc2~10^2~16 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=524724ed1f224875a117be593540591ed050c73d Btrfs: fdatasync should skip metadata writeout In btrfs, fdatasync and fsync are identical, but 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. --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 Signed-off-by: Hisashi Hifumi Signed-off-by: Chris Mason --- diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 0726a73..126477e 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1157,6 +1157,8 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync) 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 */