Michael, given the approach is accepted by Carlos and Roland, I have some minor textual suggestions for the patch itself. On 06/26/2015 10:05 PM, Michael Kerrisk (man-pages) wrote: > --- a/man2/sched_setaffinity.2 > +++ b/man2/sched_setaffinity.2 > @@ -223,6 +223,47 @@ system call returns the size (in bytes) of the > .I cpumask_t > data type that is used internally by the kernel to > represent the CPU set bit mask. > +.SS Handling systems with more than 1024 CPUs What if the system has exactly 1024 CPUs ? Suggestion: systems with 1024 or more CPUs > +The > +.I cpu_set_t > +data type used by glibc has a fixed size of 128 bytes, > +meaning that the maximum CPU number that can be represented is 1023. > +.\" FIXME . See https://sourceware.org/bugzilla/show_bug.cgi?id=15630 > +.\" and https://sourceware.org/ml/libc-alpha/2013-07/msg00288.html No objection, although I have never really noticed external references in man-pages (esp. web refs). Shouldn't these be generally avoided ? (and yes, I have noticed the FIXME) > +If the system has more than 1024 CPUs, then calls of the form: 1024 or more CPUs. > + > + sched_getaffinity(pid, sizeof(cpu_set_t), &mask); > + > +will fail with the error > +.BR EINVAL , > +the error produced by the underlying system call for the case where the > +.I mask > +size specified in > +.I cpusetsize > +is smaller than the size of the affinity mask used by the kernel. > +.PP > +The underlying system calls (which represent CPU masks as bit masks of type > +.IR "unsigned long\ *" ) > +impose no restriction on the size of the mask. > +To handle systems with more than 1024 CPUs, one must dynamically allocate the > +.I mask > +argument using > +.BR CPU_ALLOC (3) I would rewrite the sentence to avoid "one must". > +and manipulate the mask using the "_S" macros described in and manipulate the macros ending with "_S" as described in > +.BR CPU_ALLOC (3). > +Using an allocation based on the number of online CPUs: > + > + cpu_set_t *mask = CPU_ALLOC(CPU_ALLOC_SIZE( > + sysconf(_SC_NPROCESSORS_CONF))); > + > +is probably sufficient, although the value returned by the > +.BR sysconf () > +call can in theory change during the lifetime of the process. > +Alternatively, one can obtain a value that is guaranteed to be stable for Like above, I would replace "one can obtain a value" by "a value can be obtained". > +the lifetime of the process by proby for the size of the required mask using s/proby/probing/. > +.BR sched_getaffinity () > +calls with increasing mask sizes until the call does not fail with the error > +.BR EINVAL . I would replace "until the call does not fail with error ..." by "while the call succeeds". Also, the sentence too long, IMHO. Best regards Tolga Dalman -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
