On 1/21/20 10:08 AM, Quentin Perret wrote:
On Monday 20 Jan 2020 at 16:20:49 (+0000), Lukasz Luba wrote:
On 1/20/20 3:28 PM, Quentin Perret wrote:
Agreed, this looks a bit confusing. It should be trivial to make
em_dev_get() (or whatever we end up calling it) work for CPUs too,
though. And we could always have a em_cpu_get(int cpu) API that is a
basically a wrapper around em_dev_get() for convenience.
The problem not only here is that we have a CPU index 'int cpu'
and if we ask for device like:
struct device *dev = get_cpu_device(cpu);
It might be not the same device that was used during the
registration, when we had i.e. 4 CPUs for the same policy:
int cpu_id = cpumask_first(policy->cpus);
struct device *cpu_dev = get_cpu_device(cpu_id);
em_register_perf_domain(cpu_dev, nr_opp, &em_cb);
That's why the em_cpu_get() is different than em_get_pd(), mainly by:
if (cpumask_test_cpu(cpu, em_span_cpus(em_pd)))
It won't be simple wrapper, let me think how it could be handled
differently than it is now.
Right so I suppose the easiest solution would be to do the opposite of
my first suggestion. That is, make em_get_pd() call em_cpu_get() if the
device is a CPU device, or proceed to the PD list iteration for other
devices. And em_cpu_get() can remain as you originally suggested (that
is, iterate over the PDs and test the mask).
Exactly, something like:
---------------------------->8-------------------------
288 struct em_perf_domain *em_get_pd(struct device *dev)
289 {
290 struct em_device *em_dev;
291
292 if (IS_ERR_OR_NULL(dev))
293 return NULL;
294
295 if (_is_cpu_device(dev))
296 return em_cpu_get(dev->id);
....
------------------------8<-----------------------------
That should ensure em_get_pd() always works, em_cpu_get() is still there
handy for the scheduler and such, and the two EM lookup functions (for
CPUs or for devices) are kept cleanly separated.
Thoughts ?
Agree. Then we can have these two functions and em_get_pd() will also
work fine.
Thanks,
Quentin
Regards,
Lukasz
