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

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Message-ID: <20100330182906.GD5211@lenovo>
Date:	Tue, 30 Mar 2010 22:29:06 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
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, 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).

	-- Cyrill
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