On Mon, Jan 24, 2022 at 01:40:49PM -0300, Marcelo Tosatti wrote:
> On Mon, Jan 24, 2022 at 05:26:26PM +0100, Sebastian Andrzej Siewior wrote:
> > On 2022-01-24 09:58:31 [-0300], Marcelo Tosatti wrote:
> > > You mean "using all CPUs which are part of the current affinity mask by
> > > default" ? (where current affinity mask would mean user specified CPU
> > > mask).
> > >
> > > > And then either specify the
> > > > requested CPU mask or use explicitly all CPUs.
> > >
> > > Do you mean to drop
> > >
> > > /*
> > > * Clear bits that are not set in both the cpuset from the
> > > * environment, and in the user specified affinity.
> > >
> > > And just attempt to use the user specified mask? (which will then return
> > > failure to the user in which case he can correct it).
> > >
> > After reading it again, I don't get it.
> > cyclictest -a
> >
> > Uses all CPUs in the system.
> >
> > cyclictest -a $CPU
> >
> > Uses the $CPU (mask) specified. If $CPU is not part of the current CPU
> > mask, why shouldn't it work?
>
> -a, --affinity[=PROC-SET]
> Run threads on the set of processors given by PROC-SET. If PROC-SET is not specified, all processors will be used. Threads will be assigned to processors
> in the set in numeric order, in a round-robin fashion.
> The set of processors can be specified as A,B,C, or A-C, or A-B,D-F, and so on*. The ! character can be used to negate a set. For example, !B-D means to
> use all available CPUs except B through D. The cpu numbers are the same as shown in the processor field in /proc/cpuinfo. See numa(3) for more
> information on specifying CPU sets. * Support for CPU sets requires libnuma version >= 2. For libnuma v1, PROC-SET, if specified, must be a single CPU
> number.
>
>
> /*
> * After this function is called, affinity_mask is the intersection of
> * the user supplied affinity mask and the affinity mask from the run
> * time environment
> */
> static void use_current_cpuset(int max_cpus, struct bitmask *cpumask)
> {
> struct bitmask *curmask;
> int i;
>
> curmask = numa_allocate_cpumask();
> numa_sched_getaffinity(getpid(), curmask);
>
> /*
> * Clear bits that are not set in both the cpuset from the
> * environment, and in the user specified affinity.
> */
> for (i = 0; i < max_cpus; i++) {
> if ((!numa_bitmask_isbitset(cpumask, i)) ||
> (!numa_bitmask_isbitset(curmask, i)))
> numa_bitmask_clearbit(cpumask, i);
> }
>
> numa_bitmask_free(curmask);
> }
>
> Consider 8 CPU system booted with isolcpus=3-7, and execution of
> "cyclictest -a 3-7".
>
> sched_getaffinity() returns mask with bits set for CPUs 0 and 1,
and 2.
> The user supplied mask has bits 3-7 set.
>
> The intersection between the user supplied mask and the affinity mask
> from the run time environment has no bits set.
>
>
>
