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protected-headers=v1; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH] cgroup/rstat: avoid disabling irqs for O(num_cpu) MIME-Version: 1.0 On Tue, Apr 01, 2025 at 05:46:41PM +0200, Mateusz Guzik = wrote: > Is this really going to suffer for toggling every 8 CPUs? that's a 50x > factor reduction As per the original patch, there's ~10x saving in max holding irqs-off, na=EFevely thinking aggregating it flushing by 8 CPUs could reduce it to (10/8) ~1.25x saving only. (OTOH, it's not 400x effect, so it's not explained completely, not all CPUs are same.) I can imagine the balanced value with this information would be around 20 CPUs (sqrt(400)). But the issue is it could as well be 4 or 32 or 8. Starting with 1 is the simplest approach without introducing magic constants or heuristics. > the temp changes like the to stay for a long time. That'd mean that no one notices the performance impact there :-) It can be easily changed later too. > that said, there is bigger fish to fry elsewhere and I have no stake > in this code, so I'm not going to mail any further about this. Thank you for spending your effort on this, it's useful reference for the future! 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