Re: Minor page faults from memory compaction causing in-band transitions

[Philippe Gerum <rpm@xenomai.org>]

Brandon Ho <brandonho667@gmail.com> writes:

> Thank you for the responses! I recently came across the
> `compact_unevictable_allowed` sysctl option and it seems like it could be a
> good fit for our use case. Setting it to 0 would prevent the kernel from
> compacting/migrating locked pages, which should eliminate the minor faults
> we're seeing during compaction.
>
> Could we possibly set `compact_unevictable_allowed=0` by default when
> CONFIG_EVL is enabled?

Definitely, yes. Thanks for chasing this issue down. This patch is going
to be merged upstream asap, you may want to apply it for a preview.

diff --git a/mm/Kconfig b/mm/Kconfig
index 7bf469354faf3..759af896a5c7b 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -648,7 +648,7 @@ config COMPACTION
 config COMPACT_UNEVICTABLE_DEFAULT
 	int
 	depends on COMPACTION
-	default 0 if PREEMPT_RT
+	default 0 if PREEMPT_RT || DOVETAIL
 	default 1
 
 #

>
> https://www.infradead.org/~mchehab/kernel_docs/admin-guide/sysctl/vm.html#compact-unevictable-allowed

-- 
Philippe.