Re: [PATCH v2 6/8] ARCv2: perf: implement exclusion of event counting in user or kernel mode

From: Peter Zijlstra
Date: Tue Aug 18 2015 - 19:37:40 EST


On Wed, Aug 05, 2015 at 06:13:32PM +0300, Alexey Brodkin wrote:
> + hwc->config = 0;
> +
> + if (is_isa_arcv2()) {
> + /* "exclude user" means "count only kernel" */
> + if (event->attr.exclude_user)
> + hwc->config |= ARC_REG_PCT_CONFIG_KERN;
> +
> + /* "exclude kernel" means "count only user" */
> + if (event->attr.exclude_kernel)
> + hwc->config |= ARC_REG_PCT_CONFIG_USER;
> + }
> +
> switch (event->attr.type) {
> case PERF_TYPE_HARDWARE:
> if (event->attr.config >= PERF_COUNT_HW_MAX)
> return -ENOENT;
> if (arc_pmu->ev_hw_idx[event->attr.config] < 0)
> return -ENOENT;
> - hwc->config = arc_pmu->ev_hw_idx[event->attr.config];
> + hwc->config |= arc_pmu->ev_hw_idx[event->attr.config];

So I would still very much like perf_event_attr::config to reflect the
value you'll program into hardware.

If you want to do that weird 4 character lookup thing, use a special
hardware event (possibly 0 if that is not a valid value), and stuff the
4 chars in ::config1
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