Hi.
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 <[EMAIL PROTECTED]>
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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