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Lunev" , Xiaoguang Wang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 12, 2022 at 10:22 PM Stefan Hajnoczi wrote= : > > On Sat, 8 Oct 2022 at 04:43, Ziyang Zhang = wrote: > > > > On 2022/10/5 12:18, Ming Lei wrote: > > > On Tue, Oct 04, 2022 at 09:53:32AM -0400, Stefan Hajnoczi wrote: > > >> On Tue, 4 Oct 2022 at 05:44, Ming Lei wrote: > > >>> > > >>> On Mon, Oct 03, 2022 at 03:53:41PM -0400, Stefan Hajnoczi wrote: > > >>>> On Fri, Sep 30, 2022 at 05:24:11PM +0800, Ming Lei wrote: > > >>>>> ublk-qcow2 is available now. > > >>>> > > >>>> Cool, thanks for sharing! > > >>>> > > >>>>> > > >>>>> So far it provides basic read/write function, and compression and= snapshot > > >>>>> aren't supported yet. The target/backend implementation is comple= tely > > >>>>> based on io_uring, and share the same io_uring with ublk IO comma= nd > > >>>>> handler, just like what ublk-loop does. > > >>>>> > > >>>>> Follows the main motivations of ublk-qcow2: > > >>>>> > > >>>>> - building one complicated target from scratch helps libublksrv A= PIs/functions > > >>>>> become mature/stable more quickly, since qcow2 is complicated a= nd needs more > > >>>>> requirement from libublksrv compared with other simple ones(loo= p, null) > > >>>>> > > >>>>> - there are several attempts of implementing qcow2 driver in kern= el, such as > > >>>>> ``qloop`` [2], ``dm-qcow2`` [3] and ``in kernel qcow2(ro)`` [4]= , so ublk-qcow2 > > >>>>> might useful be for covering requirement in this field > > >>>>> > > >>>>> - performance comparison with qemu-nbd, and it was my 1st thought= to evaluate > > >>>>> performance of ublk/io_uring backend by writing one ublk-qcow2 = since ublksrv > > >>>>> is started > > >>>>> > > >>>>> - help to abstract common building block or design pattern for wr= iting new ublk > > >>>>> target/backend > > >>>>> > > >>>>> So far it basically passes xfstest(XFS) test by using ublk-qcow2 = block > > >>>>> device as TEST_DEV, and kernel building workload is verified too.= Also > > >>>>> soft update approach is applied in meta flushing, and meta data > > >>>>> integrity is guaranteed, 'make test T=3Dqcow2/040' covers this ki= nd of > > >>>>> test, and only cluster leak is reported during this test. > > >>>>> > > >>>>> The performance data looks much better compared with qemu-nbd, se= e > > >>>>> details in commit log[1], README[5] and STATUS[6]. And the test c= overs both > > >>>>> empty image and pre-allocated image, for example of pre-allocated= qcow2 > > >>>>> image(8GB): > > >>>>> > > >>>>> - qemu-nbd (make test T=3Dqcow2/002) > > >>>> > > >>>> Single queue? > > >>> > > >>> Yeah. > > >>> > > >>>> > > >>>>> randwrite(4k): jobs 1, iops 24605 > > >>>>> randread(4k): jobs 1, iops 30938 > > >>>>> randrw(4k): jobs 1, iops read 13981 write 14001 > > >>>>> rw(512k): jobs 1, iops read 724 write 728 > > >>>> > > >>>> Please try qemu-storage-daemon's VDUSE export type as well. The > > >>>> command-line should be similar to this: > > >>>> > > >>>> # modprobe virtio_vdpa # attaches vDPA devices to host kernel > > >>> > > >>> Not found virtio_vdpa module even though I enabled all the followin= g > > >>> options: > > >>> > > >>> --- vDPA drivers > > >>> vDPA device simulator core > > >>> vDPA simulator for networking device > > >>> vDPA simulator for block device > > >>> VDUSE (vDPA Device in Userspace) support > > >>> Intel IFC VF vDPA driver > > >>> Virtio PCI bridge vDPA driver > > >>> vDPA driver for Alibaba ENI > > >>> > > >>> BTW, my test environment is VM and the shared data is done in VM to= o, and > > >>> can virtio_vdpa be used inside VM? > > >> > > >> I hope Xie Yongji can help explain how to benchmark VDUSE. > > >> > > >> virtio_vdpa is available inside guests too. Please check that > > >> VIRTIO_VDPA ("vDPA driver for virtio devices") is enabled in "Virtio > > >> drivers" menu. > > >> > > >>> > > >>>> # modprobe vduse > > >>>> # qemu-storage-daemon \ > > >>>> --blockdev file,filename=3Dtest.qcow2,cache.direct=3Dof|off,= aio=3Dnative,node-name=3Dfile \ > > >>>> --blockdev qcow2,file=3Dfile,node-name=3Dqcow2 \ > > >>>> --object iothread,id=3Diothread0 \ > > >>>> --export vduse-blk,id=3Dvduse0,name=3Dvduse0,num-queues=3D$(= nproc),node-name=3Dqcow2,writable=3Don,iothread=3Diothread0 > > >>>> # vdpa dev add name vduse0 mgmtdev vduse > > >>>> > > >>>> A virtio-blk device should appear and xfstests can be run on it > > >>>> (typically /dev/vda unless you already have other virtio-blk devic= es). > > >>>> > > >>>> Afterwards you can destroy the device using: > > >>>> > > >>>> # vdpa dev del vduse0 > > >>>> > > >>>>> > > >>>>> - ublk-qcow2 (make test T=3Dqcow2/022) > > >>>> > > >>>> There are a lot of other factors not directly related to NBD vs ub= lk. In > > >>>> order to get an apples-to-apples comparison with qemu-* a ublk exp= ort > > >>>> type is needed in qemu-storage-daemon. That way only the differenc= e is > > >>>> the ublk interface and the rest of the code path is identical, mak= ing it > > >>>> possible to compare NBD, VDUSE, ublk, etc more precisely. > > >>> > > >>> Maybe not true. > > >>> > > >>> ublk-qcow2 uses io_uring to handle all backend IO(include meta IO) = completely, > > >>> and so far single io_uring/pthread is for handling all qcow2 IOs an= d IO > > >>> command. > > >> > > >> qemu-nbd doesn't use io_uring to handle the backend IO, so we don't > > > > > > I tried to use it via --aio=3Dio_uring for setting up qemu-nbd, but n= ot succeed. > > > > > >> know whether the benchmark demonstrates that ublk is faster than NBD= , > > >> that the ublk-qcow2 implementation is faster than qemu-nbd's qcow2, > > >> whether there are miscellaneous implementation differences between > > >> ublk-qcow2 and qemu-nbd (like using the same io_uring context for bo= th > > >> ublk and backend IO), or something else. > > > > > > The theory shouldn't be too complicated: > > > > > > 1) io uring passthough(pt) communication is fast than socket, and io = command > > > is carried over io_uring pt commands, and should be fast than virio > > > communication too. > > > > > > 2) io uring io handling is fast than libaio which is taken in the > > > test on qemu-nbd, and all qcow2 backend io(include meta io) is handle= d > > > by io_uring. > > > > > > https://github.com/ming1/ubdsrv/blob/master/tests/common/qcow2_common > > > > > > 3) ublk uses one single io_uring to handle all io commands and qcow2 > > > backend IOs, so batching handling is common, and it is easy to see > > > dozens of IOs/io commands handled in single syscall, or even more. > > > > > >> > > >> I'm suggesting measuring changes to just 1 variable at a time. > > >> Otherwise it's hard to reach a conclusion about the root cause of th= e > > >> performance difference. Let's learn why ublk-qcow2 performs well. > > > > > > Turns out the latest Fedora 37-beta doesn't support vdpa yet, so I bu= ilt > > > qemu from the latest github tree, and finally it starts to work. And = test kernel > > > is v6.0 release. > > > > > > Follows the test result, and all three devices are setup as single > > > queue, and all tests are run in single job, still done in one VM, and > > > the test images are stored on XFS/virito-scsi backed SSD. > > > > > > The 1st group tests all three block device which is backed by empty > > > qcow2 image. > > > > > > The 2nd group tests all the three block devices backed by pre-allocat= ed > > > qcow2 image. > > > > > > Except for big sequential IO(512K), there is still not small gap betw= een > > > vdpa-virtio-blk and ublk. > > > > > > 1. run fio on block device over empty qcow2 image > > > 1) qemu-nbd > > > running qcow2/001 > > > run perf test on empty qcow2 image via nbd > > > fio (nbd(/mnt/data/ublk_null_8G_nYbgF.qcow2), libaio, bs 4k, di= o, hw queues:1)... > > > randwrite: jobs 1, iops 8549 > > > randread: jobs 1, iops 34829 > > > randrw: jobs 1, iops read 11363 write 11333 > > > rw(512k): jobs 1, iops read 590 write 597 > > > > > > > > > 2) ublk-qcow2 > > > running qcow2/021 > > > run perf test on empty qcow2 image via ublk > > > fio (ublk/qcow2( -f /mnt/data/ublk_null_8G_s761j.qcow2), libaio= , bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0). > > > randwrite: jobs 1, iops 16086 > > > randread: jobs 1, iops 172720 > > > randrw: jobs 1, iops read 35760 write 35702 > > > rw(512k): jobs 1, iops read 1140 write 1149 > > > > > > 3) vdpa-virtio-blk > > > running debug/test_dev > > > run io test on specified device > > > fio (vdpa(/dev/vdc), libaio, bs 4k, dio, hw queues:1)... > > > randwrite: jobs 1, iops 8626 > > > randread: jobs 1, iops 126118 > > > randrw: jobs 1, iops read 17698 write 17665 > > > rw(512k): jobs 1, iops read 1023 write 1031 > > > > > > > > > 2. run fio on block device over pre-allocated qcow2 image > > > 1) qemu-nbd > > > running qcow2/002 > > > run perf test on pre-allocated qcow2 image via nbd > > > fio (nbd(/mnt/data/ublk_data_8G_sc0SB.qcow2), libaio, bs 4k, di= o, hw queues:1)... > > > randwrite: jobs 1, iops 21439 > > > randread: jobs 1, iops 30336 > > > randrw: jobs 1, iops read 11476 write 11449 > > > rw(512k): jobs 1, iops read 718 write 722 > > > > > > 2) ublk-qcow2 > > > running qcow2/022 > > > run perf test on pre-allocated qcow2 image via ublk > > > fio (ublk/qcow2( -f /mnt/data/ublk_data_8G_yZiaJ.qcow2), libaio= , bs 4k, dio, hw queues:1, uring_comp: 0, get_data: 0). > > > randwrite: jobs 1, iops 98757 > > > randread: jobs 1, iops 110246 > > > randrw: jobs 1, iops read 47229 write 47161 > > > rw(512k): jobs 1, iops read 1416 write 1427 > > > > > > 3) vdpa-virtio-blk > > > running debug/test_dev > > > run io test on specified device > > > fio (vdpa(/dev/vdc), libaio, bs 4k, dio, hw queues:1)... > > > randwrite: jobs 1, iops 47317 > > > randread: jobs 1, iops 74092 > > > randrw: jobs 1, iops read 27196 write 27234 > > > rw(512k): jobs 1, iops read 1447 write 1458 > > > > > > > > > > Hi All, > > > > We are interested in VDUSE vs UBLK, too. And I have tested them with nu= llblk backend. > > Let me share some results here. > > > > I setup UBLK with: > > ublk add -t loop -f /dev/nullb0 -d QUEUE_DEPTH -q NR_QUEUE > > > > I setup VDUSE with: > > qemu-storage-daemon \ > > --chardev socket,id=3Dcharmonitor,path=3D/tmp/qmp.sock,server=3D= on,wait=3Doff \ > > --monitor chardev=3Dcharmonitor \ > > --blockdev driver=3Dhost_device,cache.direct=3Don,filename=3D/de= v/nullb0,node-name=3Ddisk0 \ > > --export vduse-blk,id=3Dtest,node-name=3Ddisk0,name=3Dvduse_test= ,writable=3Don,num-queues=3DNR_QUEUE,queue-size=3DQUEUE_DEPTH > > > > Here QUEUE_DEPTH is 1, 32 or 128 and NR_QUEUE is 1 or 4. > > > > Note: > > (1) VDUSE requires QUEUE_DEPTH >=3D 2. I cannot setup QUEUE_DEPTH to 1. > > (2) I use qemu 7.1.0-rc3. It supports vduse-blk. > > (3) I do not use ublk null target so that the test is fair. > > (4) I setup fio with direct=3D1, bs=3D4k. > > > > ------------------------------ > > 1 job 1 iodepth, lat=EF=BC=88usec) > > vduse ublk > > seq-read 22.55 11.15 > > rand-read 22.49 11.17 > > seq-write 25.67 10.25 > > rand-write 24.13 10.16 > > Thanks for sharing. Any idea what the bottlenecks are for vduse and ublk? > I think one reason for the latency gap of sync I/O is that vduse uses workqueue in the I/O completion path but ublk doesn't. And one bottleneck for the async I/O in vduse is that vduse will do memcpy inside the critical section of virtqueue's spinlock in the virtio-blk driver. That will hurt the performance heavily when virtio_queue_rq() and virtblk_done() run concurrently. And it can be mitigated by the advance DMA mapping feature [1] or irq binding support [2]. [1] https://lwn.net/Articles/886029/ [2] https://www.spinics.net/lists/kvm/msg236244.html Thanks, Yongji > Stefan > > > > > ------------------------------ > > 1 job 32 iodepth, iops=EF=BC=88k) > > vduse ublk > > seq-read 166 207 > > rand-read 150 204 > > seq-write 131 359 > > rand-write 129 363 > > > > ------------------------------ > > 4job 128 iodepth, iops (k) > > > > vduse ublk > > seq-read 318 984 > > rand-read 307 929 > > seq-write 221 924 > > rand-write 217 917 > > > > Regards, > > Zhang