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 13:58:29 +0100 [thread overview]
Message-ID: <20150109125829.GF29390@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150109125507.GD495@console-pimps.org>
On Fri, Jan 09, 2015 at 12:55:07PM +0000, Matt Fleming wrote:
> On Wed, 07 Jan, at 01:16:17PM, Peter Zijlstra wrote:
> > On Fri, Nov 14, 2014 at 09:15:11PM +0000, Matt Fleming wrote:
> > + /*
> > > + * A reasonable upper limit on the max threshold is the number
> > > + * of lines tagged per RMID if all RMIDs have the same number of
> > > + * lines tagged in the LLC.
> > > + *
> > > + * For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC.
> > > + */
> > > + __intel_cqm_max_threshold =
> > > + boot_cpu_data.x86_cache_size * 1024 / (cqm_max_rmid + 1);
> >
> > Seeing how a percentage is without unit, the 35MB figure seems
> > pointless.
>
> It's only an example to demonstrate that this fudge calculation makes
> sense on the current class of CQM-enabled hardware.
>
> > Also, why would a flat distribution be a good measure for 'empty'? I
> > would think that would in fact constitute in use.
>
> It's not, it's a good measure for 'full'. This is the *max* threshold.
> When searching for RMIDs to stabilize we'll stop searching if
> __intel_cqm_threshold == __intel_cqm_max_threshold, since that indicates
> all our RMIDs have *so* many lines tagged that it's unlikely increasing
> __intel_cqm_threshold any further would be a win.
Right, but we'll also consider RMIDs with less than this as fit for
reuse. So we'll re-use RMIDs that are effectively full.
Our aim is to acquire an 'empty' RMID, not give up and start reusing
full ones just because, right?
next prev parent reply other threads:[~2015-01-09 12:58 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
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 [this message]
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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