Commit 7b2489d3 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

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.orgSigned-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e3df4c6e
...@@ -512,6 +512,17 @@ config PSI_DEFAULT_DISABLED ...@@ -512,6 +512,17 @@ config PSI_DEFAULT_DISABLED
per default but can be enabled through passing psi=1 on the per default but can be enabled through passing psi=1 on the
kernel commandline during boot. 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" endmenu # "CPU/Task time and stats accounting"
config CPU_ISOLATION config CPU_ISOLATION
......
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