[CC += "Paul Jackson" <pj@xxxxxxx>, who might want to Ack the patch below] >> This might be obvious to all of you, but it wasn't to me... The CPU set used >> for the affinity is the intersection of the set passed to >> pthread_setaffinity_np() and the set of processors supported by the >> kernel... >> >> That's why your example shall work, even if the system where it runs has >> less than 8 processors. > > It's true. The page should say something to make this clearer. I > added this text to NOTES > > After a call to pthread_setaffinity_np(3), the set of > CPUs on which the thread will actually run is the inter- > section of the set specified in the cpuset argument and > the set of CPUs actually present on the system. The sys- > tem may further restrict the set of CPUs on which the > thread runs if the "cpuset" mechanism described in > cpuset(7) is being used. These restrictions on the > actual set of CPUs on which the thread will run are > silently imposed by the kernel. Of course, the sched_setaffinity.2 page also deserves similar text. I made the change below. Look ok? Cheers, Michael --- a/man2/sched_setaffinity.2 +++ b/man2/sched_setaffinity.2 @@ -122,7 +122,10 @@ A supplied memory address was invalid. .B EINVAL The affinity bit mask .I mask -contains no processors that are physically on the system. +contains no processors that are currently physically on the system +and permitted to the process according to any restrictions that +may be imposed by the "cpuset" mechanism described in +.BR cpuset (7). .TP .B EINVAL .RB ( sched_getaffinity () @@ -157,6 +160,19 @@ argument was removed, but was then restored in glibc 2.3.4, with type .SH "CONFORMING TO" These system calls are Linux-specific. .SH "NOTES" +After a call to +.BR sched_setaffinity (), +the set of CPUs on which the process will actually run is +the intersection of the set specified in the +.I mask +argument and the set of CPUs actually present on the system. +The system may further restrict the set of CPUs on which the process +runs if the "cpuset" mechanism described in +.BR cpuset (7) +is being used. +These restrictions on the actual set of CPUs on which the process +will run are silently imposed by the kernel. + .BR sched_setscheduler (2) has a description of the Linux scheduling scheme. .PP -- 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
