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From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: acme@kernel.org, jolsa@kernel.org, linux-kernel@vger.kernel.org,
	Andi Kleen <ak@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 01/11] x86, perf: Support sysfs files depending on SMT status
Date: Thu, 28 Apr 2016 10:17:48 +0200
Message-ID: <20160428081748.GP24771@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160428080609.GU3430@twins.programming.kicks-ass.net>

On Thu, Apr 28, 2016 at 10:06:09AM +0200, Peter Zijlstra wrote:
> On Wed, Apr 27, 2016 at 01:00:41PM -0700, Andi Kleen wrote:
> > From: Andi Kleen <ak@linux.intel.com>
> > 
> > Add a way to show different sysfs events attributes depending on
> > HyperThreading is on or off. This is difficult to determine
> > early at boot, so we just do it dynamically when the sysfs
> > attribute is read.
> 
> Thomas would like to have this in the general (x86) topology bits.
> 
> Because having SMT enabled (or not) is not something perf specific (nor
> Intel, because apparently AMD is going to do proper SMT too with their
> Zen micro-arch), and might very well be useful for other thingies to
> know.
> 
> So I suppose it should end up somewhere around:
> 
>   /sys/devices/system/cpu/

FWIW I think we already can tell if SMT is enabled by doing something
like:

for i in /sys/devices/system/cpu/cpu*/topology/thread_siblings_list;
do
	SMT=`cat $i | awk --field-separator "," '{print NF}'`;
	if [ $SMT -gt 1 ] ; then
		echo ENABLED;
		break;
	fi;
done

With pretty much the same races as this interface has, no?

In any case, a single value is certainly easier than the above.

  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-27 20:00 Add top down metrics to perf stat Andi Kleen
2016-04-27 20:00 ` [PATCH 01/11] x86, perf: Support sysfs files depending on SMT status Andi Kleen
2016-04-28  8:06   ` Peter Zijlstra
2016-04-28  8:17     ` Peter Zijlstra [this message]
2016-04-27 20:00 ` [PATCH 02/11] x86, perf: Add Top Down events to Intel Core Andi Kleen
2016-04-27 20:00 ` [PATCH 03/11] x86, perf: Add Top Down events to Intel Atom Andi Kleen
2016-04-27 20:00 ` [PATCH 04/11] x86, perf: Use new ht_on flag in HT leak workaround Andi Kleen
2016-04-27 20:00 ` [PATCH 05/11] perf, tools: Parse an .aggr-per-core event attribute Andi Kleen
2016-04-27 20:00 ` [PATCH 06/11] perf, tools, stat: Force --per-core mode for .aggr-per-core aliases Andi Kleen
2016-04-27 20:00 ` [PATCH 07/11] perf, tools, stat: Avoid fractional digits for integer scales Andi Kleen
2016-04-27 20:00 ` [PATCH 08/11] perf, tools, stat: Scale values by unit before metrics Andi Kleen
2016-04-27 20:00 ` [PATCH 09/11] perf, tools, stat: Basic support for TopDown in perf stat Andi Kleen
2016-04-27 20:00 ` [PATCH 10/11] perf, tools, stat: Add computation of TopDown formulas Andi Kleen
2016-04-27 20:00 ` [PATCH 11/11] perf, tools, stat: Add extra output of counter values with -vv Andi Kleen
2016-05-07  4:57   ` [tip:perf/core] perf " tip-bot for Andi Kleen
  -- strict thread matches above, loose matches on Subject: below --
2016-04-04 20:41 Add top down metrics to perf stat Andi Kleen
2016-04-04 20:41 ` [PATCH 01/11] x86, perf: Support sysfs files depending on SMT status Andi Kleen
2016-03-22 23:08 Add top down metrics to perf stat Andi Kleen
2016-03-22 23:08 ` [PATCH 01/11] x86, perf: Support sysfs files depending on SMT status Andi Kleen

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