On Tue, 2015-03-31 at 15:59 +0100, Filipe Manana wrote: [snip]
> From: Filipe Manana <[email protected]> > Date: Tue, 31 Mar 2015 14:16:52 +0100 > Subject: [PATCH] Btrfs: avoid syncing log in the fast fsync path when not > necessary > > Commit 3a8b36f37806 ("Btrfs: fix data loss in the fast fsync path") added > a performance regression for that causes an unnecessary sync of the log > trees (fs/subvol and root log trees) when 2 consecutive fsyncs are done > against a file, without no writes or any metadata updates to the inode in > between them and if a transaction is committed before the second fsync is > called. > > Huang Ying reported this to lkml after a test sysbench test that measured > a -62% decrease of file io requests for that tests' workload. > > The test is: > > echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor > echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor > echo performance > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor > echo performance > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor > mkfs -t btrfs /dev/sda2 > mount -t btrfs /dev/sda2 /fs/sda2 > cd /fs/sda2 > for ((i = 0; i < 1024; i++)); do fallocate -l 67108864 testfile.$i; done > sysbench --test=fileio --max-requests=0 --num-threads=4 --max-time=600 \ > --file-test-mode=rndwr --file-total-size=68719476736 --file-io-mode=sync \ > --file-num=1024 run > > A test on kvm guest, running a debug kernel gave me the following results: > > Without 3a8b36f378060d: 16.01 reqs/sec > With 3a8b36f378060d: 3.39 reqs/sec > With 3a8b36f378060d and this patch: 16.04 reqs/sec > > Reported-by: Huang Ying <[email protected]> I have tested your patch, the regression restored in our test. Thanks! Tested-by: Huang, Ying <[email protected]> Best Regards, Huang, Ying [snip] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
