linux-kernel - Re: [PATCH 0/3] perf/core, x86: unify perfctr bitmasks

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Date:	Tue, 30 Mar 2010 21:04:00 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Robert Richter <robert.richter@....com>,
	Stephane Eranian <eranian@...gle.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>
Subject: Re: [PATCH 0/3] perf/core, x86: unify perfctr bitmasks

On Tue, 2010-03-30 at 22:29 +0400, Cyrill Gorcunov wrote:
> On Tue, Mar 30, 2010 at 06:55:13PM +0200, Peter Zijlstra wrote:
> [...]
> > -static int p4_hw_config(struct perf_event_attr *attr, struct hw_perf_event *hwc)
> > +static int p4_hw_config(struct perf_event *event)
> >  {
> >  	int cpu = raw_smp_processor_id();
> >  	u32 escr, cccr;
> > @@ -444,11 +431,29 @@ static int p4_hw_config(struct perf_even
> >  	 */
> >  
> >  	cccr = p4_default_cccr_conf(cpu);
> > -	escr = p4_default_escr_conf(cpu, attr->exclude_kernel, attr->exclude_user);
> > -	hwc->config = p4_config_pack_escr(escr) | p4_config_pack_cccr(cccr);
> > +	escr = p4_default_escr_conf(cpu, event->attr.exclude_kernel,
> > +					 event->attr.exclude_user);
> > +	event->hw.config = p4_config_pack_escr(escr) |
> > +			   p4_config_pack_cccr(cccr);
> >  
> >  	if (p4_ht_active() && p4_ht_thread(cpu))
> > -		hwc->config = p4_set_ht_bit(hwc->config);
> > +		event->hw.config = p4_set_ht_bit(event->hw.config);
> > +
> > +	if (event->attr.type != PERF_TYPE_RAW)
> > +		return 0;
> > +
> > +	/*
> > +	 * We don't control raw events so it's up to the caller
> > +	 * to pass sane values (and we don't count the thread number
> > +	 * on HT machine but allow HT-compatible specifics to be
> > +	 * passed on)
> > +	 *
> > +	 * XXX: HT wide things should check perf_paranoid_cpu() &&
> > +	 *      CAP_SYS_ADMIN
> > +	 */
> > +	event->hw.config |= event->attr.config &
> > +		(p4_config_pack_escr(P4_ESCR_MASK_HT) |
> > +		 p4_config_pack_cccr(P4_CCCR_MASK_HT));
> >  
> >  	return 0;
> >  }
> [...]
> 
> P4 events thread specific is a bit more messy in compare with
> architectural events. There are thread specific (TS) and thread
> independent (TI) events. The exact effect of mixing flags from
> what we call "ANY" bit is described in two matrix in SDM.
> 
> So to make code simplier I chose to just bind events to a
> particular logical cpu, when event migrate to say a second cpu
> the bits just flipped in accordance on which cpu the event is
> going to run. Pretty simple. Even more -- if there was some
> RAW event which have set "ANY" bit -- they all will be just stripped
> and event get bound to a single cpu.
> 
> I'll try to find out an easy way to satisfy this "ANY" bit request
> though it would require some time (perhaps today later or rather
> tomorrow).

Right, so don't worry about actively supporting ANY on regular events,
wider than logical cpu counting is a daft thing.

What would be nice to detect is if the raw event provided would be a TI
(ANY) event, in which case we should apply the extra paranoia.

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