path: root/init
diff options
authorJohannes Weiner <hannes@cmpxchg.org>2019-02-01 14:21:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-02-01 15:46:24 -0800
commit7b2489d37e1e355228f7c55724f77580e1dec22a (patch)
tree51ae035f64cbed04a867484904466ca63e044e3a /init
parente3df4c6e4836ce93cd5cf92d9cbdeaf4439a0241 (diff)
psi: clarify the Kconfig text for the default-disable option
The current help text caused some confusion in online forums about whether or not to default-enable or default-disable psi in vendor kernels. This is because it doesn't communicate the reason for why we made this setting configurable in the first place: that the overhead is non-zero in an artificial scheduler stress test. Since this isn't representative of real workloads, and the effect was not measurable in scheduler-heavy real world applications such as the webservers and memcache installations at Facebook, it's fair to point out that this is a pretty cautious option to select. Link: http://lkml.kernel.org/r/20190129233617.16767-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'init')
1 files changed, 11 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig
index 354146666d97..c9386a365eea 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -512,6 +512,17 @@ config PSI_DEFAULT_DISABLED
per default but can be enabled through passing psi=1 on the
kernel commandline during boot.
+ This feature adds some code to the task wakeup and sleep
+ paths of the scheduler. The overhead is too low to affect
+ common scheduling-intense workloads in practice (such as
+ webservers, memcache), but it does show up in artificial
+ scheduler stress tests, such as hackbench.
+ If you are paranoid and not sure what the kernel will be
+ used for, say Y.
+ Say N if unsure.
endmenu # "CPU/Task time and stats accounting"