From aa71ac2f9d4ad7443e4959c59a81962b0ec210b3 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Fri, 1 Feb 2019 14:21:15 -0800 Subject: [PATCH] UPSTREAM: 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 Reviewed-by: Andrew Morton Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds (cherry picked from commit 7b2489d37e1e355228f7c55724f77580e1dec22a) Bug: 127712811 Test: lmkd in PSI mode Change-Id: I5d0cb901562fd74c82d9d211544745b802776d8a Signed-off-by: Suren Baghdasaryan --- init/Kconfig | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index f3fcc15f57cf..92ae180bb084 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -507,6 +507,17 @@ 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" source "kernel/rcu/Kconfig" -- 2.20.1