Date: Wed, 5 May 2021 17:04:53 +0300 (MSK) From: Alexander Monakov <amonakov@...ras.ru> To: musl@...ts.openwall.com cc: Vincent Donnefort <vincent.donnefort@....com> Subject: Re: [PATCH] sysconf: add _SC_NPROCESSORS_CONF support 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
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