On Tue, Feb 21, 2017 at 10:48:06AM -0600, shiva rkreddy wrote: > fio command without fsync: > > # fio -filename=/dev/bcache0 -direct=1 -ioengine=libaio -rw=randwrite > -bs=4k -name=mytest -iodepth=1 -runtime=30 -time_based > > iops : 35k > > fio command with fsync: > > fio -filename=/dev/bcache0 -direct=1 -ioengine=libaio -rw=randwrite > -bs=4k -name=mytest -iodepth=1 -runtime=30 -time_based -fsync=1 > > iops: 8.1k > I'm quite surprised by the drop in iops with fsync turned on. Is this > expected or am I missing some basic setting? It's not uncommon that fsync would have a huge performance impact. Without fsync, most of the data never hits the storage and is only staying in the system memory. May I suggest that you try to measure the performance of the same tests when the filesystem is created on the NVMe device directly, without using bcache? You're likely to observe a similar pattern. -- Vojtech Pavlik Director SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
