Re: [PATCH 06/13] irq: add a helper spread an affinity mask for MSI/MSI-X vectors

On Thu, Jun 30, 2016 at 07:48:54PM +0200, Christoph Hellwig wrote:

On Sat, Jun 25, 2016 at 10:05:19PM +0200, Alexander Gordeev wrote:

quoted

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+ * and generate an output cpumask suitable for spreading MSI/MSI-X vectors
+ * so that they are distributed as good as possible around the CPUs.  If
+ * more vectors than CPUs are available we'll map one to each CPU,

Unless I do not misinterpret a loop from msix_setup_entries() (patch 08/13),
the above is incorrect:

What part do you think is incorrect?

With your explanations below and no immediate intention to fix the
algorithm it is correct.

quoted

(*) I guess, in some topology configurations a total number of all
first siblings may be less than the number of vectors.

Yes, in that case we'll assign imcompetely.  I've already heard people
complaining about that at LSF/MM, but no one volunteered patches.
I only have devices with 1 or enough vectores to test, so I don't
really dare to touch the algorithm.  Either way the algorithm
change should probably be a different patch than refactoring it and
moving it around.

I see your approach now. Thanks!