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From: Alexander Monakov <amonakov@ispras.ru>
To: musl@lists.openwall.com
Cc: Vincent Donnefort <vincent.donnefort@arm.com>
Subject: Re: [musl] [PATCH] sysconf: add _SC_NPROCESSORS_CONF support
Date: Wed, 5 May 2021 17:04:53 +0300 (MSK)
Message-ID: <alpine.LNX.2.20.13.2105051702240.5297@monopod.intra.ispras.ru> (raw)
In-Reply-To: <20210505130615.6222-1-vincent.donnefort@arm.com>



On Wed, 5 May 2021, Vincent Donnefort wrote:

> Currently, _SC_NPROCESSORS_CONF is always equal to _SC_NPROCESSORS_ONLN.
> However, it is expected from the first one to give the total number of CPUs
> in the system, while the later must return only the number of CPUs which
> are currently online. This distinction is important for a software such as
> trace-cmd. Trace-cmd is a front-end for the kernel tracing tool ftrace.
> When recording traces, trace-cmd needs to get the total number of CPUs
> available in the system (_SC_NPROCESSORS_CONF) and not only the online ones
> otherwise if a CPU goes offline some data might be missing.
> 
> Hence, add a specific method to get _SC_NPROCESSORS_CONF, based on the
> sysfs CPU entries /sys/devices/system/cpu/cpu[0-9]

Why do the opendir instead of reading from /sys/devices/system/cpu/possible?
The online/offline/possible CPU masks are documented in
linux/Documentation/ABI/testing/sysfs-devices-system-cpu and
linux/Documentation/cputopology.txt

Alexander

  reply	other threads:[~2021-05-05 14:05 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05 13:06 Vincent Donnefort
2021-05-05 14:04 ` Alexander Monakov [this message]
2021-05-05 17:05   ` Vincent Donnefort
2021-05-05 17:20   ` James Y Knight

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