Messages in this thread | | | Date | Thu, 26 Jan 2012 09:28:22 -0800 | From | Dave Hansen <> | Subject | Re: [PATCH] mm: implement WasActive page flag (for improving cleancache) |
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On 01/25/2012 01:58 PM, Dan Magenheimer wrote: > (Feedback welcome if there is a different/better way to do this > without using a page flag!) > > Since about 2.6.27, the page replacement algorithm maintains > an "active" bit to help decide which pages are most eligible > to reclaim, see http://linux-mm.org/PageReplacementDesign > > This "active' information is also useful to cleancache but is lost > by the time that cleancache has the opportunity to preserve the > pageful of data. This patch adds a new page flag "WasActive" to > retain the state. The flag may possibly be useful elsewhere.
I guess cleancache itself is clearing the bit, right? I didn't see any clearing going on in the patch.
I do think it also needs to get cleared on the way in to the page allocator. Otherwise:
PageSetWasActive(page); free_page(page); ... another_user_page = get_free_page() // now cleancache sees the active bit for the prev user
Or am I missing somewhere it gets cleared non-explicitly somewhere?
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