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Re: [PATCH v1] domctl: hold domctl lock while domain is destroyed

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Fri, 17 Sep 2021 08:17:02 +0200
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  • Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Dmitry Isaikin <isaikin-dmitry@xxxxxxxxx>
  • Delivery-date: Fri, 17 Sep 2021 06:17:12 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 16.09.2021 19:52, Andrew Cooper wrote:
> On 16/09/2021 13:30, Jan Beulich wrote:
>> On 16.09.2021 13:10, Dmitry Isaikin wrote:
>>> From: Dmitry Isaykin <isaikin-dmitry@xxxxxxxxx>
>>> This significantly speeds up concurrent destruction of multiple domains on 
>>> x86.
>> This effectively is a simplistic revert of 228ab9992ffb ("domctl:
>> improve locking during domain destruction"). There it was found to
>> actually improve things;
> Was it?  I recall that it was simply an expectation that performance
> would be better...

My recollection is that it was, for one of our customers.

> Amazon previously identified 228ab9992ffb as a massive perf hit, too.

Interesting. I don't recall any mail to that effect.

> Clearly some of the reasoning behind 228ab9992ffb was flawed and/or
> incomplete, and it appears as if it wasn't necessarily a wise move in
> hindsight.

Possible; I continue to think though that the present observation wants
properly understanding instead of more or less blindly undoing that




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