linux-kernel - Re: [PATCH 01/11] x86, perf: Support sysfs files depending on SMT status

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Message-ID: <20160428080609.GU3430@twins.programming.kicks-ass.net>
Date:	Thu, 28 Apr 2016 10:06:09 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	acme@...nel.org, jolsa@...nel.org, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 01/11] x86, perf: Support sysfs files depending on SMT
 status

On Wed, Apr 27, 2016 at 01:00:41PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.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/