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Commit 925d82a4 authored by Ben Hutchings's avatar Ben Hutchings Committed by Jeff Vander Stoep
Browse files

BACKPORT: perf tools: Document the perf sysctls 



perf_event_paranoid was only documented in source code and a perf error
message.  Copy 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: default avatarBen Hutchings <ben@decadent.org.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/20160119213515.GG2637@decadent.org.uk


[ Remove reference to external Documentation file, provide info inline, as before ]
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>

Bug: 29054680
Change-Id: I13e73cfb2ad761c94762d0c8196df7725abdf5c5
parent c5c74d03

Documentation/sysctl/kernel.txt

+27 −14
Original line number Diff line number Diff line
@@ -54,8 +54,10 @@ show up in /proc/sys/kernel: 
- overflowuid

- panic

- panic_on_oops

- panic_on_unrecovered_nmi

- panic_on_stackoverflow

- panic_on_unrecovered_nmi

- perf_cpu_time_max_percent

- perf_event_paranoid

- pid_max

- powersave-nap               [ PPC only ]

- printk
@@ -527,19 +529,6 @@ the recommended setting is 60. 


==============================================================



panic_on_unrecovered_nmi:



The default Linux behaviour on an NMI of either memory or unknown is

to continue operation. For many environments such as scientific

computing it is preferable that the box is taken out and the error

dealt with than an uncorrected parity/ECC error get propagated.



A small number of systems do generate NMI's for bizarre random reasons

such as power management so the default is off. That sysctl works like

the existing panic controls already in that directory.



==============================================================



panic_on_oops:



Controls the kernel's behaviour when an oops or BUG is encountered.
@@ -563,6 +552,19 @@ This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled. 


==============================================================



panic_on_unrecovered_nmi:



The default Linux behaviour on an NMI of either memory or unknown is

to continue operation. For many environments such as scientific

computing it is preferable that the box is taken out and the error

dealt with than an uncorrected parity/ECC error get propagated.



A small number of systems do generate NMI's for bizarre random reasons

such as power management so the default is off. That sysctl works like

the existing panic controls already in that directory.



==============================================================



perf_cpu_time_max_percent:



Hints to the kernel how much CPU time it should be allowed to
@@ -589,6 +591,17 @@ 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:

tools/perf/util/evsel.c

+9 −6
Original line number Diff line number Diff line
@@ -2067,12 +2067,15 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target, 
	case EPERM:

	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",

		 "You may not have permission to collect %sstats.\n\n"

		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"

		 "which controls use of the performance events system by\n"

		 "unprivileged users (without CAP_SYS_ADMIN).\n\n"

		 "The default value is 1:\n\n"

		 "  -1: Allow use of (almost) all events by all users\n"

		 ">= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK\n"

		 ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n"

		 ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN",

				 target->system_wide ? "system-wide " : "");

	case ENOENT:

		return scnprintf(msg, size, "The %s event is not supported.",