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Re: [PATCH] support for accessing CPU/core count (processor-count)

From: Arthur Miller
Subject: Re: [PATCH] support for accessing CPU/core count (processor-count)
Date: Mon, 11 Oct 2021 19:17:03 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux)

Paul Eggert <eggert@cs.ucla.edu> writes:

> On 10/10/21 5:21 AM, Stefan Kangas wrote:
>> Omar Polo <op@omarpolo.com> writes:
>>> OpenBSD disables hyperthreading by default so HW_NCPU is (almost) always
>>> misleading.  For example, on my machine
>>>          % uname -a
>>>          OpenBSD venera 7.0 GENERIC.MP#221 amd64
>>>          % sysctl hw.ncpu
>>>          hw.ncpu=8
>>>          % sysctl hw.ncpuonline
>>>          hw.ncpuonline=4
>>> and this has been the case for a while already (I mean, a couple of
>>> years if not more.)
>> BTW, Gnulib doesn't seem to make this distinction (lib/nproc.c:313).
>> Maybe that should be reported to the Gnulib developers?
> No need for a bug report as I'm one of those developers. To fix the Gnulib 
> nproc
> OpenBSD issue I installed the first attached patch into Gnulib, and to port
> Emacs's recently-added processor-count code to more platforms I installed the
> second attached patch into Emacs's emacs-28 branch. Although I think the 
> latter
> patch means that emacs/src/w32proc.c's w32-get-nproc function can be removed,
> I'll let the Emacs MS-Windows experts opine on that.

So you just included entire nproc into Emacs :).  Ok. Anyway; it only gives
number of "logical cores" when "hyperthreading" is on not physical. I don't
think nproc can give you that either.

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