Re: [Xen-devel] [PATCH] xen/sched: Re-position the domain_update_node_affinity() call during vcpu construction

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Sep 06, 2018 at 03:01:35PM +0100, Andrew Cooper wrote:
> alloc_vcpu()'s call to domain_update_node_affinity() has existed for a decade,
> but its effort is mostly wasted.
> 
> alloc_vcpu() is called in a loop for each vcpu, bringing them into existence.
> The values of the affinity masks are still default, which is allcpus in
> general, or a processor singleton for pinned domains.
> 
> Furthermore, domain_update_node_affinity() itself loops over all vcpus
> accumulating the masks, making it a scalability concern with large numbers of
> vcpus.
> 
> Move it to be called once after all vcpus are constructed, which has the same
> net effect, but with fewer intermediate memory allocations and less cpumask
> arithmetic.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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