Kevin, what about this one?
Pavel Dovgalyuk > -----Original Message----- > From: Pavel Dovgalyuk [mailto:[email protected]] > Sent: Wednesday, March 06, 2019 5:01 PM > To: 'Kevin Wolf' > Cc: 'Pavel Dovgalyuk'; [email protected]; [email protected]; > [email protected]; > [email protected]; [email protected]; > [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected] > Subject: RE: [PATCH v13 19/25] replay: add BH oneshot event for block layer > > > From: Kevin Wolf [mailto:[email protected]] > > Am 06.03.2019 um 10:37 hat Pavel Dovgalyuk geschrieben: > > > > From: Kevin Wolf [mailto:[email protected]] > > > > Am 06.03.2019 um 10:18 hat Pavel Dovgalyuk geschrieben: > > > > > > Something like: > > > > > > > > > > > > -drive file=null-co://,if=none,id=null -device virtio-blk,drive=null > > > > > > > > > > And this drive should be destination of the copy operations, right? > > > > > > > > I don't know your exact benchmark, but this drive should be where the > > > > high I/O rates are, yes. > > > > > > Ok. > > > > > > > For getting meaningful numbers, you should have I/O only on the fast > > > > test disk (you're talking about a copy, where is source?), > > > > > > We used a qcow2 image as a source. > > > > So the source is going to slow down the I/O and you won't actually test > > whether the possible maximum changes. > > > > > > you should > > > > use direct I/O to get the page cache of the guest out of the way, and > > > > you should make sure that multiple requests are issued in parallel. > > > > > > Is this possible, if we have only conventional HDDs? > > > > null-co:// doesn't access your disk at all, so if this is the only > > virtual disk that has I/O, the conventional HDD doesn't hurt. But you're > > right that you probably can't use your physical disk for high > > performance benchmarks then. > > > > I'm going to suggest once more to use fio for storage testing. Actually, > > maybe I can find the time to do this myself on my system, too. > > We've made some testing with the following fio configs: > > [readtest] > blocksize=4k > filename=/dev/vda > rw=randread > direct=1 > buffered=0 > ioengine=libaio > iodepth=32 > > [writetest] > blocksize=4k > filename=/dev/vda > rw=randwrite > direct=1 > buffered=0 > ioengine=libaio > iodepth=32 > > One with read, one with write, and one with both. > > master branch: > 1 read : io=1024.0MB, bw=475545KB/s, iops=118886, runt= 2205msec > > 2 write: io=1024.0MB, bw=445444KB/s, iops=111361, runt= 2354msec > > 3 read : io=1024.0MB, bw=229850KB/s, iops=57462, runt= 4562msec > write: io=1024.0MB, bw=227210KB/s, iops=56802, runt= 4615msec > > rr branch: > 1 read : io=1024.0MB, bw=479021KB/s, iops=119755, runt= 2189msec > 2 write: io=1024.0MB, bw=440763KB/s, iops=110190, runt= 2379msec > > 3 read : io=1024.0MB, bw=230456KB/s, iops=57614, runt= 4550msec > write: io=1024.0MB, bw=228548KB/s, iops=57136, runt= 4588msec > > It seems that the difference can't be measured in our environment. > > Pavel Dovgalyuk
