Re: [Xen-devel] [PATCH RESEND 3/4] xen: sched: improve checking soft-affinity

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 03/15/2018 06:35 PM, Dario Faggioli wrote:
> From: Dario Faggioli <raistlin@xxxxxxxx>
> 
> Whether or not a vCPU has a soft-affinity which is
> effective, i.e., with the power of actually affecting
> the scheduling of the vCPU itself, happens in an
> helper function, called has_soft_affinity().

This is a bit confusing; what about something like this:

"has_soft_affinity() determines whether the soft-affinity of a vcpu will
have any effect -- that is, whether the affinity will have any
difference, scheduling-wise, from an empty soft-affinity mask."

> Such function takes a custom cpumask as its third
> parameter, for better flexibility, but that mask is
> different from the vCPU's hard-affinity only in one
> case. Getting rid of that parameter, not only simplify
> the function, but enables for optimizing the soft
> affinity check (which will happen, in a subsequent
> commit).

There are a number of extraneous commas and one grammar mistake here:

"Such a function takes a custom cpumask as its third parameter[] for
better flexibility; but that mask is different from the vCPU's
hard-affinity in only one case.  Getting rid of that parameter[] not
only simplif[ies] the function, but enables [] optimizing the soft
affinity check."

> This commit, therefore, does that. It's mostly
> mechanical, with the only exception _csched_cpu_pick()
> (in Credit1 code).

The first sentence is unnecessary; I'd just say:

"It's mostly mechanical, with the exception of
sched_credit.c:_cshed_cpu_pick(), which was the one case where we passed
in something other than the existing hard-affinity."

> Signed-off-by: Dario Faggioli <raistlin@xxxxxxxx>

If you're OK with those changes, I can make them on check-in (as well as
changing your email address)

Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>

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