From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D1B5C4332F for ; Thu, 13 Oct 2022 16:02:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229832AbiJMQCg (ORCPT ); Thu, 13 Oct 2022 12:02:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229891AbiJMQCd (ORCPT ); Thu, 13 Oct 2022 12:02:33 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C77B32EE5 for ; Thu, 13 Oct 2022 09:02:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1665676950; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QAEadMmwtSWk7jIsNig6ebwX12HPHFKKzISFhVsQXlE=; b=UlVAirgITyocW8DqPLaPdlgT7em4qvtkuJXGYjaCY+N+/qrJdTc66u8wB07efGTraOBdw0 0JhZ4Idu2dtegCltz7ryKI+5JsNa+2f83wMZ+4L6/h282LY7LOGwdjcNQ5wUtUHSMAhTm/ ZhNBvYwr0blZkUWFkwDUdslKqMlDK5M= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-637-fvgWsj-fPQ-rxIQxwUv6vQ-1; Thu, 13 Oct 2022 12:02:28 -0400 X-MC-Unique: fvgWsj-fPQ-rxIQxwUv6vQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 02B27811E84; Thu, 13 Oct 2022 16:02:27 +0000 (UTC) Received: from localhost (unknown [10.39.194.71]) by smtp.corp.redhat.com (Postfix) with ESMTP id 421ED40369AB; Thu, 13 Oct 2022 16:02:25 +0000 (UTC) Date: Thu, 13 Oct 2022 12:02:23 -0400 From: Stefan Hajnoczi To: Yongji Xie Cc: Stefan Hajnoczi , Ziyang Zhang , Ming Lei , io-uring@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel , "Denis V. Lunev" , Xiaoguang Wang Subject: Re: ublk-qcow2: ublk-qcow2 is available Message-ID: References: <50827796-af93-4af5-4121-dc13c31a67fc@linux.alibaba.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="6LmWUr7zOCud/8Xx" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org --6LmWUr7zOCud/8Xx Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Oct 13, 2022 at 02:48:04PM +0800, Yongji Xie wrote: > On Wed, Oct 12, 2022 at 10:22 PM Stefan Hajnoczi wro= te: > > > > 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 wrot= e: > > > >>> > > > >>> 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 a= nd snapshot > > > >>>>> aren't supported yet. The target/backend implementation is comp= letely > > > >>>>> based on io_uring, and share the same io_uring with ublk IO com= mand > > > >>>>> handler, just like what ublk-loop does. > > > >>>>> > > > >>>>> Follows the main motivations of ublk-qcow2: > > > >>>>> > > > >>>>> - building one complicated target from scratch helps libublksrv= APIs/functions > > > >>>>> become mature/stable more quickly, since qcow2 is complicated= and needs more > > > >>>>> requirement from libublksrv compared with other simple ones(l= oop, null) > > > >>>>> > > > >>>>> - there are several attempts of implementing qcow2 driver in ke= rnel, 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 thoug= ht to evaluate > > > >>>>> performance of ublk/io_uring backend by writing one ublk-qcow= 2 since ublksrv > > > >>>>> is started > > > >>>>> > > > >>>>> - help to abstract common building block or design pattern for = writing new ublk > > > >>>>> target/backend > > > >>>>> > > > >>>>> So far it basically passes xfstest(XFS) test by using ublk-qcow= 2 block > > > >>>>> device as TEST_DEV, and kernel building workload is verified to= o. Also > > > >>>>> soft update approach is applied in meta flushing, and meta data > > > >>>>> integrity is guaranteed, 'make test T=3Dqcow2/040' covers this = kind of > > > >>>>> test, and only cluster leak is reported during this test. > > > >>>>> > > > >>>>> The performance data looks much better compared with qemu-nbd, = see > > > >>>>> details in commit log[1], README[5] and STATUS[6]. And the test= covers both > > > >>>>> empty image and pre-allocated image, for example of pre-allocat= ed 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 follow= ing > > > >>> 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 = too, 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 "Virt= io > > > >> drivers" menu. > > > >> > > > >>> > > > >>>> # modprobe vduse > > > >>>> # qemu-storage-daemon \ > > > >>>> --blockdev file,filename=3Dtest.qcow2,cache.direct=3Dof|of= f,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 dev= ices). > > > >>>> > > > >>>> 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 = ublk. In > > > >>>> order to get an apples-to-apples comparison with qemu-* a ublk e= xport > > > >>>> type is needed in qemu-storage-daemon. That way only the differe= nce is > > > >>>> the ublk interface and the rest of the code path is identical, m= aking 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 = and 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= not succeed. > > > > > > > >> know whether the benchmark demonstrates that ublk is faster than N= BD, > > > >> 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 = both > > > >> 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 i= o 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 hand= led > > > > by io_uring. > > > > > > > > https://github.com/ming1/ubdsrv/blob/master/tests/common/qcow2_comm= on > > > > > > > > 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 = the > > > >> performance difference. Let's learn why ublk-qcow2 performs well. > > > > > > > > Turns out the latest Fedora 37-beta doesn't support vdpa yet, so I = built > > > > qemu from the latest github tree, and finally it starts to work. An= d 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, a= nd > > > > 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-alloc= ated > > > > qcow2 image. > > > > > > > > Except for big sequential IO(512K), there is still not small gap be= tween > > > > 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, = dio, 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), liba= io, 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, = dio, 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), liba= io, 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 = nullblk 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= =3Don,wait=3Doff \ > > > --monitor chardev=3Dcharmonitor \ > > > --blockdev driver=3Dhost_device,cache.direct=3Don,filename=3D/= dev/nullb0,node-name=3Ddisk0 \ > > > --export vduse-blk,id=3Dtest,node-name=3Ddisk0,name=3Dvduse_te= st,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 ubl= k? > > >=20 > 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. >=20 > 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]. >=20 > [1] https://lwn.net/Articles/886029/ > [2] https://www.spinics.net/lists/kvm/msg236244.html Thanks! Stefan --6LmWUr7zOCud/8Xx Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmNINo8ACgkQnKSrs4Gr c8igXwgAhCjzhmL3oO5vNnRpRAsXBnH9HAmNVDaWOe+LN3l043ZTqL32uLVPz/la R3OXf82bSy8fWZ/gXTqEIEKDnBBucNt7kOLv8vJh9aEY6a00pX/mGbGmd9A/NwBx tpcj9DhxQ54aOIWBhpMjFr4j2pX4fgmff1EAVlagXkJOWwLcsMCkZDV5wUSmkwaE n+ZVFwWslCgBdNdKGgyHqKhtssmSRhTVHO6RrunibG8n4Ipv/NsTQpPQrbp1elpK TuywI9zSZdDvYD0SjLvpQ5AhOXBvD8OdrYmVt692zCss1Khy7U4U+ucuFzTRodgu 0G9M/6FeqzpvgmRPZmX7cTH5OAapVA== =51po -----END PGP SIGNATURE----- --6LmWUr7zOCud/8Xx--