From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56337) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XqjHZ-0006gi-0L for qemu-devel@nongnu.org; Tue, 18 Nov 2014 08:57:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XqjHU-0003NL-HL for qemu-devel@nongnu.org; Tue, 18 Nov 2014 08:57:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51644) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XqjHU-0003MO-AY for qemu-devel@nongnu.org; Tue, 18 Nov 2014 08:57:20 -0500 Message-ID: <546B5034.1050102@redhat.com> Date: Tue, 18 Nov 2014 14:57:08 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1415518978-2837-1-git-send-email-ming.lei@canonical.com> In-Reply-To: <1415518978-2837-1-git-send-email-ming.lei@canonical.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 00/13] linux-aio/virtio-scsi: support AioContext wide IO submission as batch List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Ming Lei , qemu-devel@nongnu.org, Peter Maydell , Stefan Hajnoczi , Kevin Wolf Cc: Fam Zheng On 09/11/2014 08:42, Ming Lei wrote: > This patch implements AioContext wide IO submission as batch, and > the idea behind is very simple: > > - linux native aio(io_submit) supports to enqueue read/write requests > to different files > > - in one AioContext, I/O requests from VM can be submitted to different > backend in host, one typical example is multi-lun scsi > > This patch changes 'struct qemu_laio_state' as per AioContext, and > multiple 'bs' can be associted with one single instance of > 'struct qemu_laio_state', then AioContext wide IO submission as batch > becomes easy to implement. > > One simple test in my laptop shows ~20% throughput improvement > on randread from VM(using AioContext wide IO batch vs. not using io batch) > with below config: > > -drive id=drive_scsi1-0-0-0,if=none,format=raw,cache=none,aio=native,file=/dev/nullb2 \ > -drive id=drive_scsi1-0-0-1,if=none,format=raw,cache=none,aio=native,file=/dev/nullb3 \ > -device virtio-scsi-pci,num_queues=4,id=scsi1,addr=07,iothread=iothread0 \ > -device scsi-disk,bus=scsi1.0,channel=0,scsi-id=1,lun=0,drive=drive_scsi1-0-0-0,id=scsi1-0-0-0 \ > -device scsi-disk,bus=scsi1.0,channel=0,scsi-id=1,lun=1,drive=drive_scsi1-0-0-1,id=scsi1-0-0-1 \ > > BTW, maybe more boost can be obtained since ~33K/sec write() system call > can be observed when this test case is running, and it might be a recent > regression(BH?). Ming, these patches are interesting. I would like to compare them with the opposite approach (and, I think, more similar to your old work) where the qemu_laio_state API is moved entirely into AioContext, with lazy allocation (reference-counted too, probably). Most of the patches would be the same, but you would replace aio_attach_aio_bs/aio_detach_aio_bs with something like aio_native_get/aio_native_unref. Ultimately block/{linux,win32}-aio.c could be merged into block/aio-{posix,win32}.c, but you do not have to do that now. Could you try that? This way we can see which API turns out to be nicer. Thanks, Paolo > This patchset can be found on below tree too: > > git://kernel.ubuntu.com/ming/qemu.git aio-io-batch.2 > > and these patches depend on "linux-aio: fix batch submission" patches > in below link: > > http://marc.info/?l=qemu-devel&m=141528663106557&w=2 > > Any comments and suggestions are welcome. > > async.c | 1 + > block.c | 16 +++ > block/linux-aio.c | 251 ++++++++++++++++++++++++++++++--------- > block/raw-aio.h | 6 +- > block/raw-posix.c | 4 +- > hw/scsi/virtio-scsi-dataplane.c | 8 ++ > hw/scsi/virtio-scsi.c | 2 - > include/block/aio.h | 27 +++++ > include/block/block.h | 3 + > 9 files changed, 259 insertions(+), 59 deletions(-) > > Thanks, > Ming Lei >