linux-kernel - Re: [PATCH 02/10] x86, perf: Support sysfs files depending on SMT status

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Message-ID: <20160509142741.GI11177@tassilo.jf.intel.com>
Date:	Mon, 9 May 2016 07:27:41 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>, acme@...nel.org,
	jolsa@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Subject: Re: [PATCH 02/10] x86, perf: Support sysfs files depending on SMT
 status

On Mon, May 09, 2016 at 11:42:19AM +0200, Peter Zijlstra wrote:
> On Thu, May 05, 2016 at 04:03:59PM -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.
> > 
> > v2:
> > Compute HT status only once in CPU online/offline hooks.
> > v3: Use topology_max_smt_threads()
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > ---
> >  arch/x86/events/core.c       | 24 ++++++++++++++++++++++++
> >  arch/x86/events/perf_event.h | 14 ++++++++++++++
> >  include/linux/perf_event.h   |  7 +++++++
> >  3 files changed, 45 insertions(+)
> > 
> 
> Should this not now live in /sys/devices/system/cpu/ ? Thomas?

This would be incompatible to all previous perf tools.

Also not clear why you would want to move such events, just
because they depend on SMT.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only