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Re: [PATCH v2] virtio: increase virtuqueue size for virtio-scsi and virt


From: Denis Plotnikov
Subject: Re: [PATCH v2] virtio: increase virtuqueue size for virtio-scsi and virtio-blk
Date: Tue, 18 Feb 2020 16:59:51 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1



On 18.02.2020 16:53, Stefan Hajnoczi wrote:
On Thu, Feb 13, 2020 at 05:59:27PM +0300, Denis Plotnikov wrote:
v1:
   * seg_max default value changing removed

---
The goal is to reduce the amount of requests issued by a guest on
1M reads/writes. This rises the performance up to 4% on that kind of
disk access pattern.

The maximum chunk size to be used for the guest disk accessing is
limited with seg_max parameter, which represents the max amount of
pices in the scatter-geather list in one guest disk request.

Since seg_max is virqueue_size dependent, increasing the virtqueue
size increases seg_max, which, in turn, increases the maximum size
of data to be read/write from a guest disk.

More details in the original problem statment:
https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg03721.html

Suggested-by: Denis V. Lunev <address@hidden>
Signed-off-by: Denis Plotnikov <address@hidden>
---
  hw/block/virtio-blk.c | 2 +-
  hw/core/machine.c     | 2 ++
  hw/scsi/virtio-scsi.c | 2 +-
  3 files changed, 4 insertions(+), 2 deletions(-)
I fixed up the "virtuqueue" typo in the commit message and the
mis-formatted commit description (git-am(1) stops including lines after
the first "---").
Actually, I sent the corrected version v3 of the patch last week. But it seems it got lost among that gigantic patch flow in the mailing list :)
Thanks for applying!

Denis

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan




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