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Re: [Qemu-devel] [PATCH] virtio: improve virtio devices initialization t
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] virtio: improve virtio devices initialization time |
Date: |
Fri, 12 Jan 2018 17:45:50 +0200 |
On Fri, Jan 12, 2018 at 10:48:21AM +0200, Gal Hammer wrote:
>
> On Thu, Jan 11, 2018 at 9:52 PM, Michael S. Tsirkin <address@hidden> wrote:
>
> On Thu, Jan 11, 2018 at 12:16:56PM +0200, Gal Hammer wrote:
> > The loading time of a VM is quite significant when its virtio
> > devices uses a large amount of virt-queues (e.g. a virtio-serial
> > device with
>
> max_ports=511). Most of the time is spend in the
> > creation of all the required event notifiers (ioeventfd and memory
> > regions).
> >
> > This patch pack all the changes to the memory regions in a
> > single memory transaction.
> >
> > Reported-by: Sitong Liu <address@hidden>
> > Reported-by: Xiaoling Gao <address@hidden>
> > Signed-off-by: Gal Hammer <address@hidden>
>
> Nice patch! Any timing numbers to share before/after?
>
>
> Thanks. Unfortunately I made a mistake in the shutdown code (the transaction
> is wrapping the code which doesn't modify the memory regions), so a V2 is on
> its way.
>
> As for the timing. Running a VM with 25 virtio-serial devices, each one with
> max_ports=511, results in a boot time of around 30 minutes. With this patch
> (and a another patch to kvm) reduce it to approximately 3 minutes.
Good to know, sounds like an important fix to have.
Since you plan to do v2 anyway, please add this info
in the commit log.
> This was reported and tracked here:
> https://bugzilla.redhat.com/show_bug.cgi?id
> =1528588
>
> Gal.