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Re: [Qemu-devel] [PATCH 1/4] multifd: Change page count default to 128
From: |
Juan Quintela |
Subject: |
Re: [Qemu-devel] [PATCH 1/4] multifd: Change page count default to 128 |
Date: |
Thu, 07 Feb 2019 13:13:51 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Daniel P. Berrangé <address@hidden> wrote:
> On Wed, Feb 06, 2019 at 02:23:28PM +0100, Juan Quintela wrote:
>> I haven't seend any problem about using 64 or 128. And it make much
>> less contention on the locks. Just change it.
>
> Isn't there a issue with having a fixed page count given the
> very different default page sizes across architectures ?
>
> x86 is 4kb pages, while ppc64 uses 64kb pages IIUC.
>
> This would mean current value of 64 pages, would correspond
> to 1/4 MB on x86, and 4 MB on ppc64. The new value would
> be 1/2 MB on x86 and 8 MB on ppc64.
I saw no difference (on x86 between 64 and 128 pages). Bigger pages
means half the contention on the locks and better for compression (see
next series).
> Should we instead be measuring this tunable in units that
> are independant of page size ? eg meansure in KB, with a
> requirement that the value is a multiple of the page size.
> Then set the default to 512 KB ?
See next patch, I just dropped the tunable altogether. Libvirt don't
want to support it (difficult to explain), and in the past you asked me
to choose a sane value and live with it O:-)
It was good for testing, though.
Once there, is there a good value for a network packet?
I put it in pages because it facilitates the coding, but doing a:
CONSTANT/qemu_target_page_size() is not going to complicate anything
either.
Later, Juan.
Re: [Qemu-devel] [PATCH 2/4] multifd: Drop x-multifd-page-count parameter, Daniel P . Berrangé, 2019/02/07
[Qemu-devel] [PATCH 3/4] multifd: Drop x-, Juan Quintela, 2019/02/06