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Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migrati
From: |
Peter Xu |
Subject: |
Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread |
Date: |
Wed, 21 Mar 2018 16:19:23 +0800 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Fri, Mar 16, 2018 at 04:05:14PM +0800, Xiao Guangrong wrote:
>
> Hi David,
>
> Thanks for your review.
>
> On 03/15/2018 06:25 PM, Dr. David Alan Gilbert wrote:
>
> > > migration/ram.c | 32 ++++++++++++++++----------------
> >
> > Hi,
> > Do you have some performance numbers to show this helps? Were those
> > taken on a normal system or were they taken with one of the compression
> > accelerators (which I think the compression migration was designed for)?
>
> Yes, i have tested it on my desktop, i7-4790 + 16G, by locally live migrate
> the VM which has 8 vCPUs + 6G memory and the max-bandwidth is limited to 350.
>
> During the migration, a workload which has 8 threads repeatedly written total
> 6G memory in the VM. Before this patchset, its bandwidth is ~25 mbps, after
> applying, the bandwidth is ~50 mbps.
Hi, Guangrong,
Not really review comments, but I got some questions. :)
IIUC this patch will only change the behavior when last_sent_block
changed. I see that the performance is doubled after the change,
which is really promising. However I don't fully understand why it
brings such a big difference considering that IMHO current code is
sending dirty pages per-RAMBlock. I mean, IMHO last_sent_block should
not change frequently? Or am I wrong?
Another follow-up question would be: have you measured how long time
needed to compress a 4k page, and how many time to send it? I think
"sending the page" is not really meaningful considering that we just
put a page into the buffer (which should be extremely fast since we
don't really flush it every time), however I would be curious on how
slow would compressing a page be.
Thanks,
>
> BTW, Compression will use almost all valid bandwidth after all of our work
> which i will post it out part by part.
>
--
Peter Xu
- [Qemu-devel] [PATCH 0/8] migration: improve and cleanup compression, guangrong . xiao, 2018/03/13
- [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, guangrong . xiao, 2018/03/13
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Dr. David Alan Gilbert, 2018/03/15
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Xiao Guangrong, 2018/03/16
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Dr. David Alan Gilbert, 2018/03/19
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread,
Peter Xu <=
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Xiao Guangrong, 2018/03/22
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Peter Xu, 2018/03/26
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Xiao Guangrong, 2018/03/26
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Peter Xu, 2018/03/27
- Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Dr. David Alan Gilbert, 2018/03/27
Re: [Qemu-devel] [PATCH 1/8] migration: stop compressing page in migration thread, Wang, Wei W, 2018/03/27