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-rw-r--r--Documentation/sysctl/kernel.txt50
1 files changed, 40 insertions, 10 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index ccd42589e124..ab7d16efa96b 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -70,12 +70,12 @@ show up in /proc/sys/kernel:
- shmall
- shmmax [ sysv ipc ]
- shmmni
-- softlockup_thresh
- stop-a [ SPARC only ]
- sysrq ==> Documentation/sysrq.txt
- tainted
- threads-max
- unknown_nmi_panic
+- watchdog_thresh
- version
==============================================================
@@ -427,6 +427,32 @@ This file shows up if CONFIG_DEBUG_STACKOVERFLOW is enabled.
==============================================================
+perf_cpu_time_max_percent:
+
+Hints to the kernel how much CPU time it should be allowed to
+use to handle perf sampling events. If the perf subsystem
+is informed that its samples are exceeding this limit, it
+will drop its sampling frequency to attempt to reduce its CPU
+usage.
+
+Some perf sampling happens in NMIs. If these samples
+unexpectedly take too long to execute, the NMIs can become
+stacked up next to each other so much that nothing else is
+allowed to execute.
+
+0: disable the mechanism. Do not monitor or correct perf's
+ sampling rate no matter how CPU time it takes.
+
+1-100: attempt to throttle perf's sample rate to this
+ percentage of CPU. Note: the kernel calculates an
+ "expected" length of each sample event. 100 here means
+ 100% of that expected length. Even if this is set to
+ 100, you may still see sample throttling if this
+ length is exceeded. Set to 0 if you truly do not care
+ how much CPU is consumed.
+
+==============================================================
+
pid_max:
@@ -604,15 +630,6 @@ without users and with a dead originative process will be destroyed.
==============================================================
-softlockup_thresh:
-
-This value can be used to lower the softlockup tolerance threshold. The
-default threshold is 60 seconds. If a cpu is locked up for 60 seconds,
-the kernel complains. Valid values are 1-60 seconds. Setting this
-tunable to zero will disable the softlockup detection altogether.
-
-==============================================================
-
tainted:
Non-zero if the kernel has been tainted. Numeric values, which
@@ -648,3 +665,16 @@ that time, kernel debugging information is displayed on console.
NMI switch that most IA32 servers have fires unknown NMI up, for
example. If a system hangs up, try pressing the NMI switch.
+
+==============================================================
+
+watchdog_thresh:
+
+This value can be used to control the frequency of hrtimer and NMI
+events and the soft and hard lockup thresholds. The default threshold
+is 10 seconds.
+
+The softlockup threshold is (2 * watchdog_thresh). Setting this
+tunable to zero will disable lockup detection altogether.
+
+==============================================================