The patch titled
Subject: psi: clarify the Kconfig text for the default-disable option
has been added to the -mm tree. Its filename is
psi-clarify-the-kconfig-text-for-the-default-disable-option.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/psi-clarify-the-kconfig-text-for-the-default-disable-option.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/psi-clarify-the-kconfig-text-for-the-default-disable-option.patch
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: 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@xxxxxxxxxxx
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
init/Kconfig | 11 +++++++++++
1 file changed, 11 insertions(+)
--- a/init/Kconfig~psi-clarify-the-kconfig-text-for-the-default-disable-option
+++ a/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"
config CPU_ISOLATION
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
psi-fix-aggregation-idle-shut-off.patch
psi-clarify-the-kconfig-text-for-the-default-disable-option.patch
fs-kernfs-add-poll-file-operation.patch
kernel-cgroup-add-poll-file-operation.patch
