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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Mike Christie <michael.christie@oracle.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
	qemu-devel@nongnu.org, fam@euphon.net,
	linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
	jasowang@redhat.com, pbonzini@redhat.com,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 00/10] vhost/qemu: thread per IO SCSI vq
Date: Wed, 18 Nov 2020 04:54:07 -0500
Message-ID: <20201118044620-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <b3343762-bb11-b750-46ec-43b5556f2b8e@oracle.com>

On Tue, Nov 17, 2020 at 01:13:14PM -0600, Mike Christie wrote:
> On 11/17/20 10:40 AM, Stefan Hajnoczi wrote:
> > On Thu, Nov 12, 2020 at 05:18:59PM -0600, Mike Christie wrote:
> >> The following kernel patches were made over Michael's vhost branch:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git/log/?h=vhost
> >>
> >> and the vhost-scsi bug fix patchset:
> >>
> >> https://lore.kernel.org/linux-scsi/20201112170008.GB1555653@stefanha-x1.localdomain/T/#t
> >>
> >> And the qemu patch was made over the qemu master branch.
> >>
> >> vhost-scsi currently supports multiple queues with the num_queues
> >> setting, but we end up with a setup where the guest's scsi/block
> >> layer can do a queue per vCPU and the layers below vhost can do
> >> a queue per CPU. vhost-scsi will then do a num_queue virtqueues,
> >> but all IO gets set on and completed on a single vhost-scsi thread.
> >> After 2 - 4 vqs this becomes a bottleneck.
> >>
> >> This patchset allows us to create a worker thread per IO vq, so we
> >> can better utilize multiple CPUs with the multiple queues. It
> >> implments Jason's suggestion to create the initial worker like
> >> normal, then create the extra workers for IO vqs with the
> >> VHOST_SET_VRING_ENABLE ioctl command added in this patchset.
> > 
> > How does userspace find out the tids and set their CPU affinity?
> > 
> 
> When we create the worker thread we add it to the device owner's cgroup,
> so we end up inheriting those settings like affinity.
> 
> However, are you more asking about finer control like if the guest is
> doing mq, and the mq hw queue is bound to cpu0, it would perform
> better if we could bind vhost vq's worker thread to cpu0? I think the
> problem might is if you are in the cgroup then we can't set a specific
> threads CPU affinity to just one specific CPU. So you can either do
> cgroups or not.

Something we wanted to try for a while is to allow userspace
to create threads for us, then specify which vqs it processes.

That would address this set of concerns ...

-- 
MST


  reply index

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12 23:18 Mike Christie
2020-11-12 23:19 ` [PATCH 1/1] qemu vhost scsi: add VHOST_SET_VRING_ENABLE support Mike Christie
2020-11-17 11:53   ` Stefan Hajnoczi
2020-12-02  9:59   ` Michael S. Tsirkin
2020-12-02 16:05     ` Michael Christie
2020-11-12 23:19 ` [PATCH 01/10] vhost: remove work arg from vhost_work_flush Mike Christie
2020-11-17 13:04   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 02/10] vhost scsi: remove extra flushes Mike Christie
2020-11-17 13:07   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 03/10] vhost poll: fix coding style Mike Christie
2020-11-17 13:07   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 04/10] vhost: support multiple worker threads Mike Christie
2020-11-12 23:19 ` [PATCH 05/10] vhost: poll support support multiple workers Mike Christie
2020-11-17 15:32   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 06/10] vhost scsi: make SCSI cmd completion per vq Mike Christie
2020-11-17 16:04   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 07/10] vhost, vhost-scsi: flush IO vqs then send TMF rsp Mike Christie
2020-11-17 16:05   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 08/10] vhost: move msg_handler to new ops struct Mike Christie
2020-11-17 16:08   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 09/10] vhost: add VHOST_SET_VRING_ENABLE support Mike Christie
2020-11-17 16:14   ` Stefan Hajnoczi
2020-11-12 23:19 ` [PATCH 10/10] vhost-scsi: create a woker per IO vq Mike Christie
2020-11-17 16:40 ` [PATCH 00/10] vhost/qemu: thread per IO SCSI vq Stefan Hajnoczi
2020-11-17 19:13   ` Mike Christie
2020-11-18  9:54     ` Michael S. Tsirkin [this message]
2020-11-19 14:00       ` Stefan Hajnoczi
2020-11-18 11:31     ` Stefan Hajnoczi
2020-11-19 14:46       ` Michael S. Tsirkin
2020-11-19 16:11         ` Mike Christie
2020-11-19 16:24           ` Stefan Hajnoczi
2020-11-19 16:43             ` Mike Christie
2020-11-19 17:08               ` Stefan Hajnoczi
2020-11-20  8:45                 ` Stefan Hajnoczi
2020-11-20 12:31                   ` Michael S. Tsirkin
2020-12-01 12:59                     ` Stefan Hajnoczi
2020-12-01 13:45                       ` Stefano Garzarella
2020-12-01 17:43                         ` Stefan Hajnoczi
2020-12-02 10:35                           ` Stefano Garzarella
2020-11-23 15:17                   ` Stefano Garzarella
2020-11-18  5:17   ` Jason Wang
2020-11-18  6:57     ` Mike Christie
2020-11-18  7:19       ` Mike Christie
2020-11-18  7:54       ` Jason Wang
2020-11-18 20:06         ` Mike Christie
2020-11-19  4:35           ` Jason Wang
2020-11-19 15:49             ` Mike Christie

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