Re: [PATCH 2/3] mm: Ensure that mark_page_accessed moves pages tothe active list

[Rik van Riel]

On 04/29/2013 12:31 PM, Mel Gorman wrote:

> A PageActive page is now added to the inactivate list.
>
> While this looks strange, I think it is sufficiently harmless that additional
> barriers to address the case is not justified.  Unfortunately, while I never
> witnessed it myself, these parallel updates potentially trigger defensive
> DEBUG_VM checks on PageActive and hence they are removed by this patch.

Could this not cause issues with __page_cache_release, called from
munmap, exit, truncate, etc.?

Could the eventual skewing of active vs inactive numbers break page
reclaim heuristics?

I wonder if we would need to move to a scheme where the PG_active bit
is always the authoritive one, and we never pass an overriding "lru"
parameter to __pagevec_lru_add.

Would memory ordering between SetPageLRU and testing for PageLRU be
enough to then prevent the statistics from going off?

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