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From: "steffen at sdaoden dot eu" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug libc/30135] New: sysconf: _SC_NPROCESSORS*: tweak? Date: Sat, 18 Feb 2023 20:25:32 +0000 [thread overview] Message-ID: <bug-30135-131@http.sourceware.org/bugzilla/> (raw) https://sourceware.org/bugzilla/show_bug.cgi?id=30135 Bug ID: 30135 Summary: sysconf: _SC_NPROCESSORS*: tweak? Product: glibc Version: 2.36 Status: UNCONFIRMED Severity: normal Priority: P2 Component: libc Assignee: unassigned at sourceware dot org Reporter: steffen at sdaoden dot eu CC: drepper.fsp at gmail dot com Target Milestone: --- #?0|kent:tmp$ cat t.c #include <stdio.h> #include <unistd.h> int main(void){ long c,o; c = sysconf(_SC_NPROCESSORS_CONF); o = sysconf(_SC_NPROCESSORS_ONLN); printf("c=%ld o=%ld\n", c, o); return 0; } On bare metal: #?0|kent:tmp$ tcc -run t.c c=8 o=4 #?0|kent:tmp$ nproc 4 But in a box with cgroup-limited CPUs: bash-5.2$ tcc -run t.c c=4 o=4 bash-5.2$ nproc 3 Could this be a "bug" in the C library, as this checks /sys/devices/system/cpu/online, /proc/stat, and only then (iirc now) uses sched_getaffinity. It documents get_nprocs(3) as "number of processors currently available in the system". But POSIX standardized these[1] as _SC_NPROCESSORS_CONF + _SC_NPROCESSORS_ONLN for sysconf(3) as well as NPROCESSORS_CONF and NPROCESSORS_ONLN for getconf(1), saying ... The maximum number of execution units | _SC_NPROCESSORS_ONLN currently available to run threads† | .... † The nature of an execution unit and the precise conditions under which an execution unit is considered to be available, or can be made available, or how many threads it can execute in parallel, are implementation-defined. Which is not the same. Implementation-defined though. But i mean if it is easy to give correct results for an execution context (i would). [1] https://austingroupbugs.net/view.php?id=339 -- You are receiving this mail because: You are on the CC list for the bug.
next reply other threads:[~2023-02-18 20:25 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-02-18 20:25 steffen at sdaoden dot eu [this message] 2023-02-18 20:26 ` [Bug libc/30135] " steffen at sdaoden dot eu 2023-02-20 20:28 ` adhemerval.zanella at linaro dot org 2023-02-20 20:50 ` steffen at sdaoden dot eu 2023-02-20 22:46 ` adhemerval.zanella at linaro dot org 2023-02-20 23:47 ` steffen at sdaoden dot eu 2023-02-21 8:59 ` sam at gentoo dot org 2023-02-21 10:25 ` fweimer at redhat dot com 2023-02-21 17:31 ` steffen at sdaoden dot eu
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