linux-kernel - [PATCH RESEND] perf: Document the perf sysctls

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Message-ID: <20160119213515.GG2637@decadent.org.uk>
Date:	Tue, 19 Jan 2016 21:35:15 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH RESEND] perf: Document the perf sysctls

perf_event_paranoid was only documented in source code and a perf
error message.  Move the documentation from the error message to
Documentation/sysctl/kernel.txt.

perf_cpu_time_max_percent was already documented but missing from the
list at the top, so add it there.

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 Documentation/sysctl/kernel.txt | 13 +++++++++++++
 tools/perf/util/evsel.c         |  7 ++-----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index af70d15..88a2c8e 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -58,6 +58,8 @@ show up in /proc/sys/kernel:
 - panic_on_stackoverflow
 - panic_on_unrecovered_nmi
 - panic_on_warn
+- perf_cpu_time_max_percent
+- perf_event_paranoid
 - pid_max
 - powersave-nap               [ PPC only ]
 - printk
@@ -624,6 +626,17 @@ allowed to execute.
 
 ==============================================================
 
+perf_event_paranoid:
+
+Controls use of the performance events system by unprivileged
+users (without CAP_SYS_ADMIN).  The default value is 1.
+
+ -1: Allow use of (almost) all events by all users
+>=0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
+>=1: Disallow CPU event access by users without CAP_SYS_ADMIN
+>=2: Disallow kernel profiling by users without CAP_SYS_ADMIN
+
+==============================================================
 
 pid_max:
 
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 397fb4e..9b4df11 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2314,11 +2314,8 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 	case EACCES:
 		return scnprintf(msg, size,
 		 "You may not have permission to collect %sstats.\n"
-		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid:\n"
-		 " -1 - Not paranoid at all\n"
-		 "  0 - Disallow raw tracepoint access for unpriv\n"
-		 "  1 - Disallow cpu events for unpriv\n"
-		 "  2 - Disallow kernel profiling for unpriv",
+		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid -\n"
+		 "see Documentation/sysctl/kernel.txt",
 				 target->system_wide ? "system-wide " : "");
 	case ENOENT:
 		return scnprintf(msg, size, "The %s event is not supported.",


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