Hi,

quoted text
> Currently fdatasync is identical to fsync in ext3,4.
> 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 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.
> 
> Thanks.
> 
> Signed-off-by :Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
  Yes, the patch looks fine. You can add
Acked-by: Jan Kara <jack@suse.cz>
  if you wish.
								Honza

quoted text
> diff -Nrup linux-2.6.24.org/fs/ext3/fsync.c linux-2.6.24/fs/ext3/fsync.c
> --- linux-2.6.24.org/fs/ext3/fsync.c	2008-01-25 07:58:37.000000000 +0900
> +++ linux-2.6.24/fs/ext3/fsync.c	2008-02-04 12:42:42.000000000 +0900
> @@ -72,6 +72,9 @@ int ext3_sync_file(struct file * file, s
>  		goto out;
>  	}
>  
> +	if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
> +		goto out;
> +
>  	/*
>  	 * The VFS has written the file data.  If the inode is unaltered
>  	 * then we need not start a commit.
> diff -Nrup linux-2.6.24.org/fs/ext4/fsync.c linux-2.6.24/fs/ext4/fsync.c
> --- linux-2.6.24.org/fs/ext4/fsync.c	2008-01-25 07:58:37.000000000 +0900
> +++ linux-2.6.24/fs/ext4/fsync.c	2008-02-04 12:43:37.000000000 +0900
> @@ -72,6 +72,9 @@ int ext4_sync_file(struct file * file, s
>  		goto out;
>  	}
>  
> +        if (datasync && !(inode->i_state & I_DIRTY_DATASYNC))
> +                goto out;
> +
>  	/*
>  	 * The VFS has written the file data.  If the inode is unaltered
>  	 * then we need not start a commit.
> 
> -
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-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs
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