Re: [PATCH 2/2] mm/page_alloc.c: add config option to sanitize freed pages
From: David Rientjes
Date: Fri Apr 24 2015 - 17:38:51 EST
On Fri, 24 Apr 2015, Anisse Astier wrote:
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 390214d..cb2df5f 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -635,3 +635,15 @@ config MAX_STACK_SIZE_MB
> changed to a smaller value in which case that is used.
> A sane initial value is 80 MB.
> +config SANITIZE_FREED_PAGES
> + bool "Sanitize memory pages after free"
> + default n
> + help
> + This option is used to make sure all pages freed are zeroed. This is
> + quite low-level and doesn't handle your slab buffers.
> + It has various applications, from preventing some info leaks to
> + helping kernel same-page merging in virtualised environments.
> + Depending on your workload, it will reduce performance of about 3%.
> + If unsure, say N.
Objection to allowing this without first enabling some other DEBUG config
option, it should never be a standalone option, but also to pretending to
have any insight into what the performance degredation of it will be. On
my systems, this would be _massive_.
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