On Mon, Jan 24, 2022 at 06:07:37PM +0100, Sebastian Andrzej Siewior wrote:
> On 2022-01-24 13:40:49 [-0300], Marcelo Tosatti wrote:
> > > 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.
> > 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.
>
> Okay. But does this make to keep? I understand that the current CPU-mask
> needs to be kept for masks like !B or !B-D. But is there a need to use
> the current CPU-mask when a specific mask has been specified by the user?
Ok, then:
1) If user specifies -a CPULIST, ignore sched_getaffinity().
2) If user specifies -a, or -a !CPULIST, use sched_getaffinity().
Will send a patch.
