linux-kernel - [tip:perf/core] perf/x86/intel/lbr: Optimize v4 LBR unfreezing

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Message-ID: <tip-425507fa5f321bb5ce1b5eb57a9586e0cf0b9802@git.kernel.org>
Date:	Tue, 4 Aug 2015 01:58:44 -0700
From:	tip-bot for Andi Kleen <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	mingo@...nel.org, tglx@...utronix.de, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, peterz@...radead.org, hpa@...or.com,
	torvalds@...ux-foundation.org
Subject: [tip:perf/core] perf/x86/intel/lbr: Optimize v4 LBR unfreezing

Commit-ID:  425507fa5f321bb5ce1b5eb57a9586e0cf0b9802
Gitweb:     http://git.kernel.org/tip/425507fa5f321bb5ce1b5eb57a9586e0cf0b9802
Author:     Andi Kleen <ak@...ux.intel.com>
AuthorDate: Sun, 10 May 2015 12:22:46 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 4 Aug 2015 10:16:58 +0200

perf/x86/intel/lbr: Optimize v4 LBR unfreezing

In Arch perfmon v4 the GLOBAL_STATUS reset automatically unfreezes
LBRs. So no need to do it manually in the LBR code. Add a check
to skip it.

v2: Move test up to beginning of function.
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: eranian@...gle.com
Link: http://lkml.kernel.org/r/1431285767-27027-9-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/perf_event_intel_lbr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 2fb5737..769a42f 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -141,6 +141,13 @@ static void __intel_pmu_lbr_enable(bool pmi)
 	u64 debugctl, lbr_select = 0, orig_debugctl;
 
 	/*
+	 * No need to unfreeze manually, as v4 can do that as part
+	 * of the GLOBAL_STATUS ack.
+	 */
+	if (pmi && x86_pmu.version >= 4)
+		return;
+
+	/*
 	 * No need to reprogram LBR_SELECT in a PMI, as it
 	 * did not change.
 	 */
--
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