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| author | Ingo Molnar <mingo@kernel.org> | 2017-12-07 01:37:06 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-12-07 01:37:06 +0300 |
| commit | d0300e5e8d2fb74852f8116f26546e12cfa66735 (patch) | |
| tree | a6580aa74a0ebd7965dbc37767717b4f73dd9d79 /Documentation/trace/coresight-cpu-debug.txt | |
| parent | c32909741fe93032705e6da29b564b8fec84f415 (diff) | |
| parent | 34c9ca37aaec2e307b837bb099d3b44f0ea04ddc (diff) | |
| download | linux-d0300e5e8d2fb74852f8116f26546e12cfa66735.tar.xz | |
Merge branch 'perf/urgent' into perf/core, to pick up fixes and to refresh to v4.15
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/trace/coresight-cpu-debug.txt')
| -rw-r--r-- | Documentation/trace/coresight-cpu-debug.txt | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/Documentation/trace/coresight-cpu-debug.txt b/Documentation/trace/coresight-cpu-debug.txt index b3da1f90b861..2b9b51cd501e 100644 --- a/Documentation/trace/coresight-cpu-debug.txt +++ b/Documentation/trace/coresight-cpu-debug.txt @@ -149,11 +149,23 @@ If you want to limit idle states at boot time, you can use "nohlt" or At the runtime you can disable idle states with below methods: -Set latency request to /dev/cpu_dma_latency to disable all CPUs specific idle -states (if latency = 0uS then disable all idle states): -# echo "what_ever_latency_you_need_in_uS" > /dev/cpu_dma_latency - -Disable specific CPU's specific idle state: +It is possible to disable CPU idle states by way of the PM QoS +subsystem, more specifically by using the "/dev/cpu_dma_latency" +interface (see Documentation/power/pm_qos_interface.txt for more +details). As specified in the PM QoS documentation the requested +parameter will stay in effect until the file descriptor is released. +For example: + +# exec 3<> /dev/cpu_dma_latency; echo 0 >&3 +... +Do some work... +... +# exec 3<>- + +The same can also be done from an application program. + +Disable specific CPU's specific idle state from cpuidle sysfs (see +Documentation/cpuidle/sysfs.txt): # echo 1 > /sys/devices/system/cpu/cpu$cpu/cpuidle/state$state/disable |