From: Paolo Bonzini <pbonzini@redhat.com>
To: Ming Lei <ming.lei@canonical.com>
Cc: Jens Axboe <axboe@kernel.dk>,
"Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Linux Virtualization <virtualization@lists.linux-foundation.org>,
Stefan Hajnoczi <stefanha@redhat.com>,
linux-api@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] block: virtio-blk: support multi virt queues per virtio-blk device
Date: Tue, 17 Jun 2014 18:34:13 +0200 [thread overview]
Message-ID: <53A06E05.9060708@redhat.com> (raw)
In-Reply-To: <CACVXFVO6GDu7Cp=s7kn_XBE2EFnuh+XQs4UQKTFaCLi4_9jcgg@mail.gmail.com>
Il 17/06/2014 18:00, Ming Lei ha scritto:
>> > If you want to do queue steering based on the guest VCPU number, the number
>> > of queues must be = to the number of VCPUs shouldn't it?
>> >
>> > I tried using a divisor of the number of VCPUs, but couldn't get the block
>> > layer to deliver interrupts to the right VCPU.
> For blk-mq's hardware queue, that won't be necessary to equal to
> VCPUs number, and irq affinity per hw queue can be simply set as
> blk_mq_hw_ctx->cpumask.
Yes, but on top of that you want to have each request processed exactly
by the CPU that sent it. Unless the cpumasks are singletons, most of
the benefit went away in my virtio-scsi tests. Perhaps blk-mq is smarter.
Can you try benchmarking a 16 VCPU guest with 8 and 16 queues?
Paolo
next prev parent reply other threads:[~2014-06-17 16:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-13 17:29 [RFC PATCH 0/2] block: virtio-blk: support multi vq per virtio-blk Ming Lei
2014-06-13 17:29 ` [RFC PATCH 1/2] include/uapi/linux/virtio_blk.h: introduce feature of VIRTIO_BLK_F_MQ Ming Lei
2014-06-16 12:42 ` Rusty Russell
2014-06-13 17:29 ` [RFC PATCH 2/2] block: virtio-blk: support multi virt queues per virtio-blk device Ming Lei
2014-06-16 12:47 ` Rusty Russell
2014-06-17 2:40 ` Stefan Hajnoczi
2014-06-17 15:50 ` Ming Lei
[not found] ` <CACVXFVO0SybUKArQbKkj2+hbk6q_gt3SBooNNmw1jErRR8d07A@mail.gmail.com>
2014-06-17 15:53 ` Paolo Bonzini
2014-06-17 16:00 ` Ming Lei
2014-06-17 16:34 ` Paolo Bonzini [this message]
2014-06-18 4:04 ` Ming Lei
[not found] ` <CACVXFVMkV5R5GUjM7Y-U54SA-ENZZ26dbbv4K2_OYPdmmiuUqg@mail.gmail.com>
2015-12-14 10:31 ` Paolo Bonzini
[not found] ` <566E9A7E.3030203@redhat.com>
2015-12-15 1:26 ` Ming Lei
2014-06-13 17:35 ` [RFC PATCH 0/2] block: virtio-blk: support multi vq per virtio-blk Jens Axboe
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