[libvirt] [PATCH] cpumap: optimize for clients that don't need online count

Doug Goldstein cardoe at gentoo.org
Fri Nov 2 16:07:24 UTC 2012

On Thu, Nov 1, 2012 at 9:58 PM, Eric Blake <eblake at redhat.com> wrote:
> On 11/01/2012 08:17 PM, Laine Stump wrote:
>> On 11/01/2012 09:57 PM, Eric Blake wrote:
>>> It turns out that calling virNodeGetCPUMap(conn, NULL, NULL, 0)
>>> is both useful, and with Viktor's patches, common enough to
>>> optimize.  Since this interface hasn't been released yet, we
>>> can change the RPC call.
>> After a small bit of explaining the context surrounding the change on
>> IRC, I understand what's going on and the benefit, and I agree that it's
>> either now or never.
>> ACK.
> Thanks.  I edited the commit message to mention some of the context
> (finding the max cpu is one sysfs file, but finding the bitmap of cpus
> to determine which cpus are online involves more file reads, possibly
> one per cpu depending on the age of the kernel, which can add up to a
> lot of worthless syscalls if the caller passed NULL for both
> parameters).  Now pushed.
> --

A bit late (sorry!) but I did go through this patch last night and I
agree with the ACK and that this is something we wanted for 1.0.0
(which is already out).

Doug Goldstein

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