lkml.org 
[lkml]   [2018]   [Oct]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Qemu-devel] virtio-console downgrade the virtio-pci-blk performance
* Feng Li (lifeng1519@gmail.com) wrote:
> Hi,
> I found an obvious performance downgrade when virtio-console combined
> with virtio-pci-blk.
>
> This phenomenon exists in nearly all Qemu versions and all Linux
> (CentOS7, Fedora 28, Ubuntu 18.04) distros.
>
> This is a disk cmd:
> -drive file=iscsi://127.0.0.1:3260/iqn.2016-02.com.test:system:fl-iscsi/1,format=raw,if=none,id=drive-virtio-disk0,cache=none,aio=native
> -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,write-cache=on
>
> If I add "-device
> virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 ", the virtio
> disk 4k iops (randread/randwrite) would downgrade from 60k to 40k.
>
> In VM, if I rmmod virtio-console, the performance will back to normal.
>
> Any idea about this issue?
>
> I don't know this is a qemu issue or kernel issue.

It sounds odd; can you provide more details on:
a) The benchmark you're using.
b) the host and the guest config (number of cpus etc)
c) Why are you running it with iscsi back to the same host - why not
just simplify the test back to a simple file?

Dave

>
> Thanks in advance.
> --
> Thanks and Best Regards,
> Alex
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

\
 
 \ /
  Last update: 2018-10-01 13:43    [W:0.068 / U:2.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site