linux-kernel - [PATCH 2/2] perf stat: Remove nmi watchdog check code again

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Date:	Wed,  8 Jun 2016 14:36:47 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	peterz@...radead.org
Cc:	acme@...nel.org, jolsa@...nel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 2/2] perf stat: Remove nmi watchdog check code again

From: Andi Kleen <ak@...ux.intel.com>

Now that the NMI watchdog runs with reference cycles, and does not
conflict with TopDown anymore, we don't need to check that the
NMI watchdog is off in perf stat --topdown.

Remove the code that does this and always use a group unconditionally.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 tools/perf/Documentation/perf-stat.txt |  6 ------
 tools/perf/arch/x86/util/Build         |  1 -
 tools/perf/arch/x86/util/group.c       | 27 ---------------------------
 tools/perf/builtin-stat.c              | 18 +-----------------
 tools/perf/util/group.h                |  7 -------
 5 files changed, 1 insertion(+), 58 deletions(-)
 delete mode 100644 tools/perf/arch/x86/util/group.c
 delete mode 100644 tools/perf/util/group.h

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index d96ccd4844df..6cf4028ddc2c 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -225,12 +225,6 @@ CPU thread. Per core mode is automatically enabled
 and -a (global monitoring) is needed, requiring root rights or
 perf.perf_event_paranoid=-1.
 
-Topdown uses the full Performance Monitoring Unit, and needs
-disabling of the NMI watchdog (as root):
-echo 0 > /proc/sys/kernel/nmi_watchdog
-for best results. Otherwise the bottlenecks may be inconsistent
-on workload with changing phases.
-
 This enables --metric-only, unless overriden with --no-metric-only.
 
 To interpret the results it is usually needed to know on which
diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
index f95e6f46ef0d..bc24b75add88 100644
--- a/tools/perf/arch/x86/util/Build
+++ b/tools/perf/arch/x86/util/Build
@@ -3,7 +3,6 @@ libperf-y += tsc.o
 libperf-y += pmu.o
 libperf-y += kvm-stat.o
 libperf-y += perf_regs.o
-libperf-y += group.o
 
 libperf-$(CONFIG_DWARF) += dwarf-regs.o
 libperf-$(CONFIG_BPF_PROLOGUE) += dwarf-regs.o
diff --git a/tools/perf/arch/x86/util/group.c b/tools/perf/arch/x86/util/group.c
deleted file mode 100644
index 37f92aa39a5d..000000000000
--- a/tools/perf/arch/x86/util/group.c
+++ /dev/null
@@ -1,27 +0,0 @@
-#include <stdio.h>
-#include "api/fs/fs.h"
-#include "util/group.h"
-
-/*
- * Check whether we can use a group for top down.
- * Without a group may get bad results due to multiplexing.
- */
-bool arch_topdown_check_group(bool *warn)
-{
-	int n;
-
-	if (sysctl__read_int("kernel/nmi_watchdog", &n) < 0)
-		return false;
-	if (n > 0) {
-		*warn = true;
-		return false;
-	}
-	return true;
-}
-
-void arch_topdown_group_warn(void)
-{
-	fprintf(stderr,
-		"nmi_watchdog enabled with topdown. May give wrong results.\n"
-		"Disable with echo 0 > /proc/sys/kernel/nmi_watchdog\n");
-}
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index dff63733dfb7..a599a78b2f22 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -59,10 +59,8 @@
 #include "util/thread.h"
 #include "util/thread_map.h"
 #include "util/counts.h"
-#include "util/group.h"
 #include "util/session.h"
 #include "util/tool.h"
-#include "util/group.h"
 #include "asm/bug.h"
 
 #include <api/fs/fs.h>
@@ -1861,16 +1859,6 @@ static int topdown_filter_events(const char **attr, char **str, bool use_group)
 	return 0;
 }
 
-__weak bool arch_topdown_check_group(bool *warn)
-{
-	*warn = false;
-	return false;
-}
-
-__weak void arch_topdown_group_warn(void)
-{
-}
-
 /*
  * Add default attributes, if there were no attributes specified or
  * if -d/--detailed, -d -d or -d -d -d is used:
@@ -2010,7 +1998,6 @@ static int add_default_attributes(void)
 
 	if (topdown_run) {
 		char *str = NULL;
-		bool warn = false;
 
 		if (stat_config.aggr_mode != AGGR_GLOBAL &&
 		    stat_config.aggr_mode != AGGR_CORE) {
@@ -2025,14 +2012,11 @@ static int add_default_attributes(void)
 
 		if (!force_metric_only)
 			metric_only = true;
-		if (topdown_filter_events(topdown_attrs, &str,
-				arch_topdown_check_group(&warn)) < 0) {
+		if (topdown_filter_events(topdown_attrs, &str, true) < 0) {
 			pr_err("Out of memory\n");
 			return -1;
 		}
 		if (topdown_attrs[0] && str) {
-			if (warn)
-				arch_topdown_group_warn();
 			err = parse_events(evsel_list, str, NULL);
 			if (err) {
 				fprintf(stderr,
diff --git a/tools/perf/util/group.h b/tools/perf/util/group.h
deleted file mode 100644
index 116debe7a995..000000000000
--- a/tools/perf/util/group.h
+++ /dev/null
@@ -1,7 +0,0 @@
-#ifndef GROUP_H
-#define GROUP_H 1
-
-bool arch_topdown_check_group(bool *warn);
-void arch_topdown_group_warn(void);
-
-#endif
-- 
2.5.5