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Re: [Qemu-devel] [PATCH v2] migration: skip sending ram pages released b
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v2] migration: skip sending ram pages released by virtio-balloon driver. |
Date: |
Wed, 13 Apr 2016 12:15:38 +0100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
* Michael S. Tsirkin (address@hidden) wrote:
> On Wed, Apr 13, 2016 at 04:24:55PM +0530, Jitendra Kolhe wrote:
> > Can we extend support for post-copy in a different patch set?
>
> If the optimization does not *help* on some paths,
> that's fine. The issue is with adding extra code
> special-casing protocols:
>
> + if (migrate_postcopy_ram()) {
> + balloon_bitmap_disable_state = BALLOON_BITMAP_DISABLE_PERMANENT;
> + }
>
> Generally when one sees that patchset breaks XYZ...
> the easy solution is "check for XYZ
> and disable the optimization". But do this enough times
> and the codebase becomes impossible to reason about.
> why did migration become slower? oh it enabled
> optimization A and that conflicts with optimization B ...
Hang on; this is getting all very complicated; I wouldn't start tieing
this thing up with postcopy yet. Lets try and keep this simple for starters.
Dave
>
>
> > and use
> > current patch set to support other remaining protocols?
>
> Even disregarding postcopy, I think there were
> comments that need to be addressed.
>
> --
> MST
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK