Currently fdatasync is identical to fsync in ext3.
I think fdatasync should skip journal flush in data=ordered and
data=writeback mode when it overwrites to already-instantiated blocks on
HDD. When I_DIRTY_DATASYNC flag is not set, fdatasync should skip journal
writeout because this indicates only atime or/and mtime updates.
Following patch is the same approach of ext2's fsync code(ext2_sync_file).
I did a performance test using the sysbench.
#sysbench --num-threads=128 --max-requests=50000 --test=fileio --file-total-size=128G
--file-test-mode=rndwr --file-fsync-mode=fdatasync run
The result on ext3 was:
-2.6.24
Operations performed: 0 Read, 50080 Write, 59600 Other = 109680 Total
Read 0b Written 782.5Mb Total transferred 782.5Mb (12.116Mb/sec)
775.45 Requests/sec executed
Test execution summary:
total time: 64.5814s
total number of events: 50080
total time taken by event execution: 3713.9836
per-request statistics:
min: 0.0000s
avg: 0.0742s
max: 0.9375s
approx. 95 percentile: 0.2901s
Threads fairness:
events (avg/stddev): 391.2500/23.26
execution time (avg/stddev): 29.0155/1.99
-2.6.24-patched
Operations performed: 0 Read, 50009 Write, 61596 Other = 111605 Total
Read 0b Written 781.39Mb Total transferred 781.39Mb (16.419Mb/sec)
1050.83 Requests/sec executed
Test execution summary:
total time: 47.5900s
total number of events: 50009
total time taken by event execution: 2934.5768
per-request statistics:
min: 0.0000s
avg: 0.0587s
max: 0.8938s
approx. 95 percentile: 0.1993s
Threads fairness:
events (avg/stddev): 390.6953/22.64
execution time (avg/stddev): 22.9264/1.17
Filesystem I/O throughput was improved.
Signed-off-by :Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Acked-by: Jan Kara <jack@suse.cz>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
53c550e975