Re: [RFC PATCH 2/2] block: virtio-blk: support multi virt queues per virtio-blk device

From: Paolo Bonzini
Date: Mon Dec 14 2015 - 05:31:38 EST

On 18/06/2014 06:04, Ming Lei wrote:
> For virtio-blk, I don't think it is always better to take more queues, and
> we need to leverage below things in host side:
> - host storage top performance, generally it reaches that with more
> than 1 jobs with libaio(suppose it is N, so basically we can use N
> iothread per device in qemu to try to get top performance)
> - iothreads' loading(if iothreads are at full loading, increasing
> queues doesn't help at all)
> In my test, I only use the current per-dev iothread(x-dataplane)
> in qemu to handle 2 vqs' notification and precess all I/O from
> the 2 vqs, and looks it can improve IOPS by ~30%.
> For virtio-scsi, the current usage doesn't make full use of blk-mq's
> advantage too because only one vq is active at the same time, so I
> guess the multi vqs' benefit won't be very much and I'd like to post
> patches to support that first, then provide test data with
> more queues(8, 16).

Hi Ming Lei,

would you like to repost these patches now that MQ support is in the kernel?

Also, I changed my mind about moving linux-aio to AioContext. I now
think it's a good idea, because it limits the number of io_getevents
syscalls. O:-) So I would be happy to review your patches for that as well.

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