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Re: [Qemu-devel] [PATCH v4 0/7] virtio-blk: multiqueue support
From: |
Christian Borntraeger |
Subject: |
Re: [Qemu-devel] [PATCH v4 0/7] virtio-blk: multiqueue support |
Date: |
Tue, 21 Jun 2016 14:25:24 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 |
On 06/21/2016 02:13 PM, Stefan Hajnoczi wrote:
> v4:
> * Rebased onto qemu.git/master
> * Included latest performance results
>
> v3:
> * Drop Patch 1 to batch guest notify for non-dataplane
>
> The Linux AIO completion BH and the virtio-blk batch notify BH changed
> order
> in the AioContext->first_bh list as a side-effect of moving the BH from
> hw/block/dataplane/virtio-blk.c to hw/block/virtio-blk.c. This caused a
> serious performance regression for both dataplane and non-dataplane.
>
> I've decided not to move the BH in this series and work on a separate
> solution for making batch notify generic.
>
> The remaining patches have been reordered and cleaned up.
>
> * See performance data below.
>
> v2:
> * Simplify s->rq live migration [Paolo]
> * Use more efficient bitmap ops for batch notification [Paolo]
> * Fix perf regression due to batch notify BH in wrong AioContext [Christian]
>
> The virtio_blk guest driver has supported multiple virtqueues since Linux
> 3.17.
> This patch series adds multiple virtqueues to QEMU's virtio-blk emulated
> device.
>
> Ming Lei sent patches previously but these were not merged. This series
> implements virtio-blk multiqueue for QEMU from scratch since the codebase has
> changed. Live migration support for s->rq was also missing from the previous
> series and has been added.
>
> It's important to note that QEMU's block layer does not support multiqueue
> yet.
> Therefore virtio-blk device processes all virtqueues in the same AioContext
> (IOThread). Further work is necessary to take advantage of multiqueue support
> in QEMU's block layer once it becomes available.
>
> Performance results:
>
> Using virtio-blk-pci,num-queues=4 can produce a speed-up but -smp 4
> introduces a lot of variance across runs. No pinning was performed.
>
> RHEL 7.2 guest on RHEL 7.2 host with 1 vcpu and 1 GB RAM unless otherwise
> noted. The default configuration of the Linux null_blk driver is used as
> /dev/vdb.
>
> $ cat files/fio.job
> [global]
> filename=/dev/vdb
> ioengine=libaio
> direct=1
> runtime=60
> ramp_time=5
> gtod_reduce=1
>
> [job1]
> numjobs=4
> iodepth=16
> rw=randread
> bs=4K
>
> $ ./analyze.py runs/
> Name IOPS Error
> v4-smp-4-dataplane 13326598.0 ± 6.31%
> v4-smp-4-dataplane-no-mq 11483568.0 ± 3.42%
> v4-smp-4-no-dataplane 18108611.6 ± 1.53%
> v4-smp-4-no-dataplane-no-mq 13951225.6 ± 7.81%
This differs from the previous numbers. What is with
and what is without patch? I am surprised to see dataplane
to be slower than no-dataplane - this contradicts everything
that I have seen in the past.
>
> Stefan Hajnoczi (7):
> virtio-blk: add VirtIOBlockConf->num_queues
> virtio-blk: multiqueue batch notify
> virtio-blk: tell dataplane which vq to notify
> virtio-blk: associate request with a virtqueue
> virtio-blk: live migrate s->rq with multiqueue
> virtio-blk: dataplane multiqueue support
> virtio-blk: add num-queues device property
>
> hw/block/dataplane/virtio-blk.c | 81
> +++++++++++++++++++++++++++++------------
> hw/block/dataplane/virtio-blk.h | 2 +-
> hw/block/virtio-blk.c | 52 +++++++++++++++++++++-----
> include/hw/virtio/virtio-blk.h | 6 ++-
> 4 files changed, 105 insertions(+), 36 deletions(-)
>
- [Qemu-devel] [PATCH v4 0/7] virtio-blk: multiqueue support, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 2/7] virtio-blk: multiqueue batch notify, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 1/7] virtio-blk: add VirtIOBlockConf->num_queues, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 5/7] virtio-blk: live migrate s->rq with multiqueue, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 3/7] virtio-blk: tell dataplane which vq to notify, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 4/7] virtio-blk: associate request with a virtqueue, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 6/7] virtio-blk: dataplane multiqueue support, Stefan Hajnoczi, 2016/06/21
- [Qemu-devel] [PATCH v4 7/7] virtio-blk: add num-queues device property, Stefan Hajnoczi, 2016/06/21
- Re: [Qemu-devel] [PATCH v4 0/7] virtio-blk: multiqueue support,
Christian Borntraeger <=
- Re: [Qemu-devel] [PATCH v4 0/7] virtio-blk: multiqueue support, Fam Zheng, 2016/06/22
- Re: [Qemu-devel] [PATCH v4 0/7] virtio-blk: multiqueue support, Stefan Hajnoczi, 2016/06/24
- [Qemu-devel] [RFC v2] virtio-blk: simple multithreaded MQ implementation for bdrv_raw, Roman Pen, 2016/06/24