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NAME="Red Hat Enterprise Linux"
VERSION="8.0 (Ootpa)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="8.0"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Red Hat Enterprise Linux 8.0 (Ootpa)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8.0:GA"
HOME_URL="https://www.redhat.com/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"
REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 8"
REDHAT_BUGZILLA_PRODUCT_VERSION=8.0
REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"
REDHAT_SUPPORT_PRODUCT_VERSION="8.0"
Handling systems with large CPU affinity masks
The underlying system calls (which represent CPU masks as bit masks
of type unsigned long *) impose no restriction on the size of the CPU
mask. However, the 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. If the kernel CPU affinity mask is larger than
1024, then calls of the form:
sched_getaffinity(pid, sizeof(cpu_set_t), &mask);
fail with the error EINVAL, the error produced by the underlying
system call for the case where the mask size specified in cpusetsize
is smaller than the size of the affinity mask used by the kernel.
(Depending on the system CPU topology, the kernel affinity mask can
be substantially larger than the number of active CPUs in the
system.)
When working on systems with large kernel CPU affinity masks, one
must dynamically allocate the mask argument (see CPU_ALLOC(3)).
The command "ppc64_cpu --frequency" failed on a Power system with 1280 threads as below:
ppc64_cpu --frequency
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
sched_setaffinity: Invalid argument
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