Re: [PATCH 2/5] mm/debug_pagealloc: don't allocate page_ext if we don't use guard page

[Vlastimil Babka]

On 08/10/2016 08:16 AM, js1304@xxxxxxxxx wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> What debug_pagealloc does is just mapping/unmapping page table.
> Basically, it doesn't need additional memory space to memorize something.
> But, with guard page feature, it requires additional memory to distinguish
> if the page is for guard or not. Guard page is only used when
> debug_guardpage_minorder is non-zero so this patch removes additional
> memory allocation (page_ext) if debug_guardpage_minorder is zero.
>
> It saves memory if we just use debug_pagealloc and not guard page.

We could also save cycles with a static key for _debug_guardpage_enabled :)

But memory savings are likely more significant, so

> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>