• Hisashi Hifumi's avatar
    ext4: fdatasync should skip metadata writeout when overwriting · 53c550e9
    Hisashi Hifumi authored
    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: default avatarJan Kara <jack@suse.cz>
    Cc: <linux-ext4@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
    53c550e9
fsync.c 2.71 KB