Commit 7b2489d3 authored Feb 01, 2019 by Johannes Weiner Committed by Linus Torvalds Feb 01, 2019

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>

parent e3df4c6e

init/Kconfig

+11 −0

Original line number	Diff line number	Diff line
		@@ -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"

		config CPU_ISOLATION

Admin message