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From: "Liang, Kan" <kan.liang@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "mingo@redhat.com" <mingo@redhat.com>,
	"acme@kernel.org" <acme@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"eranian@google.com" <eranian@google.com>,
	"jolsa@kernel.org" <jolsa@kernel.org>,
	"ak@linux.intel.com" <ak@linux.intel.com>
Subject: RE: [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI
Date: Thu, 23 Mar 2017 20:48:06 +0000	[thread overview]
Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077536BE9A6@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <20170323203138.li45llrzfxcaqieu@hirez.programming.kicks-ass.net>

> On Thu, Mar 23, 2017 at 11:25:49AM -0700, kan.liang@intel.com wrote:
> > From: Kan Liang <Kan.liang@intel.com>
> >
> > When setting FREEZE_WHILE_SMM bit in IA32_DEBUGCTL, all
> performance
> > counters will be effected. There is no way to do per-counter freeze on
> > smi. So it should not use the per-event interface (e.g. ioctl or event
> > attribute) to set FREEZE_WHILE_SMM bit.
> >
> > Adds sysfs entry /sys/device/cpu/freeze_on_smi to set
> FREEZE_WHILE_SMM
> > bit in IA32_DEBUGCTL. When set, freezes perfmon and trace messages
> > while in SMM.
> > Value has to be 0 or 1. It will be applied to all possible cpus.
> 
> So is there ever a good reason to not set this?

For me, I don't see any drawbacks to set it unconditionally.
But I'm not sure if there is someone else who may want the counter
running in SMI.

If there is no objection, I will set the FREEZE_WHILE_SMM bit
unconditionally in next version.

Thanks,
Kan 

  reply	other threads:[~2017-03-23 20:48 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-23 18:25 [PATCH 0/3]measure SMI cost kan.liang
2017-03-23 18:25 ` [PATCH 1/3] perf/x86: add sysfs entry to freeze counter on SMI kan.liang
2017-03-23 20:31   ` Peter Zijlstra
2017-03-23 20:48     ` Liang, Kan [this message]
2017-03-23 22:23     ` Andi Kleen
2017-03-24  8:16       ` Peter Zijlstra
2017-03-23 20:32   ` Peter Zijlstra
2017-03-24  8:31     ` Thomas Gleixner
2017-03-24 14:15       ` Liang, Kan
2017-03-24 14:23         ` Peter Zijlstra
2017-03-23 18:25 ` [PATCH 2/3] tools lib api fs: Add sysfs__write_int function kan.liang
2017-03-28  3:38   ` Elliott, Robert (Persistent Memory)
2017-03-23 18:25 ` [PATCH 3/3] perf stat: Add support to measure SMI cost kan.liang
2017-03-24  8:44 ` [PATCH 0/3]measure " Thomas Gleixner
2017-03-24 11:40   ` Andi Kleen
2017-03-24 12:07     ` Thomas Gleixner
2017-03-24 14:14       ` Liang, Kan
2017-03-31 21:51 ` Stephane Eranian
2017-04-01  1:41   ` Liang, Kan

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