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Re: [PATCH 1/3] x86/mem_sharing: option to skip populating special pages during fork
- To: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Fri, 25 Mar 2022 11:59:14 +0100
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- Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Tue, Mar 22, 2022 at 01:41:37PM -0400, Tamas K Lengyel wrote:
> Add option to the fork memop to skip populating the fork with special pages.
> These special pages are only necessary when setting up forks to be fully
> functional with a toolstack. For short-lived forks where no toolstack is
> active
> these pages are uneccesary.
Replying here because there's no cover letter AFAICT.
For this kind of performance related changes it would be better if you
could provide some figures about the performance impact. It would help
if we knew whether avoiding mapping the vAPIC page means you can
create 0.1% more forks per-minute or 20%.
If you really want to speed up the forking path it might be good to start
by perf sampling Xen in order to find the bottlenecks?
Thanks, Roger.
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