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From: Peter Zijlstra <peterz@infradead.org>
To: Matt Fleming <matt@console-pimps.org>
Cc: Ingo Molnar <mingo@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Andi Kleen <andi@firstfloor.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Kanaka Juvva <kanaka.d.juvva@intel.com>,
	Matt Fleming <matt.fleming@intel.com>
Subject: Re: [PATCH v4 10/11] perf/x86/intel: Perform rotation on Intel CQM RMIDs
Date: Fri, 9 Jan 2015 16:58:35 +0100	[thread overview]
Message-ID: <20150109155835.GJ29390@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150109152442.GG495@console-pimps.org>

On Fri, Jan 09, 2015 at 03:24:42PM +0000, Matt Fleming wrote:
> On Fri, 09 Jan, at 02:02:50PM, Peter Zijlstra wrote:
> > On Fri, Jan 09, 2015 at 12:14:01PM +0000, Matt Fleming wrote:
> > > On Tue, 06 Jan, at 06:17:12PM, Peter Zijlstra wrote:
> > > > 
> > > > afaict the again label will try and steal yet another rmid, if rmids
> > > > don't decay fast enough, we could end up with all rmids on the limbo
> > > > list and none active. Or am I missing something here?
> > > 
> > > You're not missing anything, that's true, we will try and steal more
> > > RMIDs. We could perhaps put a limit on how many RMIDs we're willing to
> > > steal, but I think it should definitely be > 1 because RMIDs can
> > > stabilize out of order.
> > > 
> > > It's worth pointing out that we only steal more RMIDs if the ones on the
> > > limbo list have been queued for the "minimum queue time" - it really is
> > > a last resort.
> > 
> > Do we really care? Why not just hold up everything until the one(s) we
> > have are low enough?
> > 
> > Yes it all blows, but would not some active be better than none active,
> > just because the stupid lines aren't clearing fast enough?
> 
> Right, but now we need a "steal limit", so we know when to stop stealing
> active RMIDs.
> 
> 	(cqm_max_rmid + 1) / 4 ?
> 
> I guess any limit is better than no limit.

Yeah, that'll work, when the free+limbo count is 1/4th the total we
should stop pulling more plugs.

  reply	other threads:[~2015-01-09 15:58 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-14 21:15 [PATCH v4 00/11] perf: Intel Cache QoS Monitoring support Matt Fleming
2014-11-14 21:15 ` [PATCH 01/11] perf tools: Parse event per-package info files Matt Fleming
2014-11-14 21:15 ` [PATCH 02/11] perf tools: Implement snapshot event file logic Matt Fleming
2014-11-14 21:15 ` [PATCH 03/11] perf: Make perf_cgroup_from_task() global Matt Fleming
2014-11-14 21:15 ` [PATCH 04/11] perf: Add ->count() function to read per-package counters Matt Fleming
2014-11-14 21:15 ` [PATCH 05/11] perf: Move cgroup init before PMU ->event_init() Matt Fleming
2014-11-14 21:15 ` [PATCH 06/11] x86: Add support for Intel Cache QoS Monitoring (CQM) detection Matt Fleming
2014-11-14 21:15 ` [PATCH 07/11] perf/x86/intel: Add Intel Cache QoS Monitoring support Matt Fleming
2014-11-14 21:15 ` [PATCH 08/11] perf/x86/intel: Implement LRU monitoring ID allocation for CQM Matt Fleming
2014-11-14 21:15 ` [PATCH v4 09/11] perf/x86/intel: Support task events with Intel CQM Matt Fleming
2014-11-14 21:15 ` [PATCH v4 10/11] perf/x86/intel: Perform rotation on Intel CQM RMIDs Matt Fleming
2015-01-06 16:13   ` Peter Zijlstra
2015-01-06 17:17   ` Peter Zijlstra
2015-01-09 12:14     ` Matt Fleming
2015-01-09 13:02       ` Peter Zijlstra
2015-01-09 15:24         ` Matt Fleming
2015-01-09 15:58           ` Peter Zijlstra [this message]
2015-01-15 15:31             ` Matt Fleming
2015-01-15 19:37             ` Matt Fleming
2015-01-06 17:36   ` Peter Zijlstra
2015-01-09 12:22     ` Matt Fleming
2015-01-09 12:59       ` Peter Zijlstra
2015-01-07 12:16   ` Peter Zijlstra
2015-01-09 12:55     ` Matt Fleming
2015-01-09 12:58       ` Peter Zijlstra
2015-01-11 10:45         ` Matt Fleming
2014-11-14 21:15 ` [PATCH 11/11] perf/x86/intel: Enable conflicting event scheduling for CQM Matt Fleming
2015-01-08 11:49   ` Peter Zijlstra
2015-01-09 12:56     ` Matt Fleming
2015-01-08 11:51   ` Peter Zijlstra
2015-01-09 14:27     ` Matt Fleming
2014-11-25 14:55 ` [PATCH v4 00/11] perf: Intel Cache QoS Monitoring support Matt Fleming
2014-12-18  7:59   ` Matt Fleming

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