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| author | Uladzislau Rezki <uladzislau.rezki@sony.com> | 2022-02-16 14:52:09 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2022-05-11 11:38:50 -0700 |
| commit | 28b3ae426598e722cf5d5ab9cc7038791b955a56 (patch) | |
| tree | 3fddab261f875fe8e828bbb42d5a190df6ad8144 /Documentation/RCU | |
| parent | 3123109284176b1532874591f7c81f3837bbdc17 (diff) | |
| download | lwn-28b3ae426598e722cf5d5ab9cc7038791b955a56.tar.gz lwn-28b3ae426598e722cf5d5ab9cc7038791b955a56.zip | |
rcu: Introduce CONFIG_RCU_EXP_CPU_STALL_TIMEOUT
Currently both expedited and regular grace period stall warnings use
a single timeout value that with units of seconds. However, recent
Android use cases problem require a sub-100-millisecond expedited RCU CPU
stall warning. Given that expedited RCU grace periods normally complete
in far less than a single millisecond, especially for small systems,
this is not unreasonable.
Therefore introduce the CONFIG_RCU_EXP_CPU_STALL_TIMEOUT kernel
configuration that defaults to 20 msec on Android and remains the same
as that of the non-expedited stall warnings otherwise. It also can be
changed in run-time via: /sys/.../parameters/rcu_exp_cpu_stall_timeout.
[ paulmck: Default of zero to use CONFIG_RCU_STALL_TIMEOUT. ]
Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'Documentation/RCU')
| -rw-r--r-- | Documentation/RCU/stallwarn.rst | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index 78404625bad2..794837eb519b 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -162,6 +162,26 @@ CONFIG_RCU_CPU_STALL_TIMEOUT Stall-warning messages may be enabled and disabled completely via /sys/module/rcupdate/parameters/rcu_cpu_stall_suppress. +CONFIG_RCU_EXP_CPU_STALL_TIMEOUT +-------------------------------- + + Same as the CONFIG_RCU_CPU_STALL_TIMEOUT parameter but only for + the expedited grace period. This parameter defines the period + of time that RCU will wait from the beginning of an expedited + grace period until it issues an RCU CPU stall warning. This time + period is normally 20 milliseconds on Android devices. A zero + value causes the CONFIG_RCU_CPU_STALL_TIMEOUT value to be used, + after conversion to milliseconds. + + This configuration parameter may be changed at runtime via the + /sys/module/rcupdate/parameters/rcu_exp_cpu_stall_timeout, however + this parameter is checked only at the beginning of a cycle. If you + are in a current stall cycle, setting it to a new value will change + the timeout for the -next- stall. + + Stall-warning messages may be enabled and disabled completely via + /sys/module/rcupdate/parameters/rcu_cpu_stall_suppress. + RCU_STALL_DELAY_DELTA --------------------- |