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

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Date:	Thu, 20 Aug 2015 11:33:54 +0000
From:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:	'Peter Zijlstra' <peterz@...radead.org>
CC:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arc-linux-dev@...opsys.com" <arc-linux-dev@...opsys.com>,
	"arnd@...db.de" <arnd@...db.de>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: RE: [PATCH v2 6/8] ARCv2: perf: implement exclusion of event
 counting in user or kernel mode

Hi Peter,

> -----Original Message-----
> From: Peter Zijlstra [mailto:peterz@...radead.org]
> Sent: 19 августа 2015 г. 2:37
> To: Alexey Brodkin
> Cc: linux-arch@...r.kernel.org; linux-kernel@...r.kernel.org; Vineet.Gupta1@...opsys.com; arc-linux-dev@...opsys.com;
> arnd@...db.de; Arnaldo Carvalho de Melo
> Subject: Re: [PATCH v2 6/8] ARCv2: perf: implement exclusion of event counting in user or kernel mode
> 
> 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

Ok I understand your concern here but I cannot quite understand
what do you mean saying "stuff the 4 chars in ::config1".

Could you please explain this a bit more verbose?
Is there an example of something similar I may take a look at?

-Alexey
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