From: Andi Kleen <andi@firstfloor.org>
To: Robert Richter <robert.richter@amd.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@elte.hu>,
Stephane Eranian <eranian@google.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] perf, x86: Use ALTERNATIVE() to check for X86_FEATURE_PERFCTR_CORE
Date: Tue, 19 Apr 2011 20:21:48 +0200 [thread overview]
Message-ID: <20110419182148.GS16484@one.firstfloor.org> (raw)
In-Reply-To: <20110419103927.GV31407@erda.amd.com>
On Tue, Apr 19, 2011 at 12:39:27PM +0200, Robert Richter wrote:
> On 18.04.11 16:00:57, Andi Kleen wrote:
> > Robert Richter <robert.richter@amd.com> writes:
> >
> > > Using ALTERNATIVE() when checking for X86_FEATURE_PERFCTR_CORE avoids
> > > an extra pointer chase and data cache hit.
> >
> > Is that really a performance critical path?
> >
> > Seems more like unnecessary obfuscation to me.
>
> We hotest path is in perf_pmu_disable(), which happens at least with
> every task switch when calling the event scheduler.
Yes but that's already a slow path isn't it? It better is, because
the MSR accesses alone are incredibly expensive. I guess your test
and jump isn't even on the radar after that ...
-Andi
next prev parent reply other threads:[~2011-04-19 18:21 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-16 0:27 [PATCH 0/4] perf, x86: Fixes for v2.6.39 Robert Richter
2011-04-16 0:27 ` [PATCH 1/4] perf, x86: Fix pre-defined cache-misses event for AMD family 15h cpus Robert Richter
2011-04-19 12:03 ` [tip:perf/urgent] " tip-bot for Andre Przywara
2011-04-16 0:27 ` [PATCH 2/4] perf, x86: Fix AMD family 15h FPU event constraints Robert Richter
2011-04-19 12:04 ` [tip:perf/urgent] " tip-bot for Robert Richter
2011-04-16 0:27 ` [PATCH 3/4] perf, x86: Use ALTERNATIVE() to check for X86_FEATURE_PERFCTR_CORE Robert Richter
2011-04-18 20:00 ` Andi Kleen
2011-04-19 10:39 ` Robert Richter
2011-04-19 18:21 ` Andi Kleen [this message]
2011-04-19 12:04 ` [tip:perf/core] " tip-bot for Robert Richter
2011-04-16 0:27 ` [PATCH 4/4] perf, x86: Fix event scheduler to solve complex scheduling problems Robert Richter
2011-04-16 8:51 ` Peter Zijlstra
2011-04-16 9:43 ` Ingo Molnar
2011-04-16 10:08 ` Peter Zijlstra
2011-04-16 10:14 ` Ingo Molnar
2011-04-16 10:15 ` Peter Zijlstra
2011-04-16 14:26 ` Valdis.Kletnieks
2011-04-17 8:15 ` Robert Richter
2011-04-17 8:18 ` Ingo Molnar
2011-04-17 8:53 ` Peter Zijlstra
2011-04-17 11:23 ` Robert Richter
2011-04-18 8:17 ` Robert Richter
2011-04-16 15:52 ` Stephane Eranian
2011-04-17 8:44 ` Robert Richter
2011-04-17 9:05 ` Stephane Eranian
2011-04-19 10:26 ` [PATCH v2] perf, x86: Fix event scheduler for constraints with overlapping counters Robert Richter
2011-04-19 11:29 ` Ingo Molnar
2011-04-19 13:55 ` Robert Richter
2011-04-28 9:50 ` Robert Richter
2011-05-18 21:16 ` Peter Zijlstra
2011-05-18 21:20 ` Ingo Molnar
2011-05-18 21:36 ` Peter Zijlstra
2011-05-19 10:49 ` Robert Richter
2011-05-19 18:06 ` Ingo Molnar
2011-05-20 3:18 ` Robert Richter
2011-09-01 12:56 ` Peter Zijlstra
2011-09-01 14:12 ` Robert Richter
2011-09-01 16:37 ` Peter Zijlstra
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