> From: Dave Hansen [mailto:dave@xxxxxxxxxxxxxxxxxx] > Subject: Re: [PATCH] mm: implement WasActive page flag (for improving cleancache) Thanks for the review Dave! > 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. No, there are no changes in cleancache.c so it isn't clearing the bit. > 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? True, it is not getting cleared and it should be, good catch! I'll find the place to add the call to ClearPageWasActive() for v2. Thanks, Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href