On Tue, Jan 08, 2019 at 11:28:02AM +0100, Peter Zijlstra wrote:
> On Mon, Jan 07, 2019 at 04:27:22PM +0000, Andrew Murray wrote:
> > @@ -393,9 +386,8 @@ __hw_perf_event_init(struct perf_event *event)
> > /*
> > * Check whether we need to exclude the counter from certain modes.
> > */
> > + if (armpmu->set_event_filter &&
> > + armpmu->set_event_filter(hwc, &event->attr)) {
> > pr_debug("ARM performance counters do not support "
> > "mode exclusion\n");
> > return -EOPNOTSUPP;
>
> This then requires all set_event_filter() implementations to check all
> the various exclude options;
Yes but this isn't a new requirement, this hunk uses the absence of
set_event_filter to blanket indicate that no exclusion flags are supported.
> also, set_event_filter() failing then
> returns with -EOPNOTSUPP instead of the -EINVAL the CAP_NO_EXCLUDE
> generates, which is again inconsitent.
Yes, it's not ideal - but a step in the right direction. I wanted to limit
user visible changes as much as possible, where I've identified them I've
noted it in the commit log.
>
> If I look at (the very first git-grep found me)
> armv7pmu_set_event_filter(), then I find it returning -EPERM (again
> inconsistent but irrelevant because the actual value is not preserved)
> for exclude_idle.
>
> But it doesn't seem to check exclude_host at all for example.
Yes I found lots of examples like this across the tree whilst doing this
work. However I decided to initially start with simply removing duplicated
code as a result of adding this flag and attempting to preserve existing
functionality. I thought that if I add missing checks then the patchset
will get much bigger and be harder to merge. I would like to do this though
as another non-cross-arch series.
Can we limit this patch series to the minimal changes required to fully
use PERF_PMU_CAP_NO_EXCLUDE and then attempt to fix these existing problems
in subsequent patch sets?
Thanks,
Andrew Murray
>
> > @@ -867,6 +859,9 @@ int armpmu_register(struct arm_pmu *pmu)
> > if (ret)
> > return ret;
> >
> > + if (!pmu->set_event_filter)
> > + pmu->pmu.capabilities |= PERF_PMU_CAP_NO_EXCLUDE;
> > +
> > ret = perf_pmu_register(&pmu->pmu, pmu->name, -1);
> > if (ret)
> > goto out_destroy;
> > --
> > 2.7.4
> >
