> Hi KOSAKI, > > On Wed, Sep 1, 2010 at 10:37 AM, KOSAKI Motohiro > <kosaki.motohiro@xxxxxxxxxxxxxx> wrote: > > When a page has PG_referenced, shrink_page_list() discard it only > > if it is no dirty. This rule works completely fine if the backend > > filesystem is regular one. PG_dirty is good signal that it was used > > recently because flusher thread clean pages periodically. In addition, > > page writeback is costly rather than simple page discard. > > > > However, When a page is on tmpfs, this heuristic don't works because > > flusher thread don't writeback tmpfs pages. then, tmpfs pages always > > rotate lru twice at least and it makes unnecessary lru churn. Merely > > tmpfs streaming io shouldn't cause large anonymous page swap-out. > > It seem to make sense. > But the why admin use tmps is to keep the contents in memory as far as > possible than other's file system. > But this patch has a possibility for tmpfs pages to reclaim early than > old behavior. > > I admit this routine's goal is not to protect tmpfs page from too early reclaim. > But at least, it would have affected until now. > If it is, we might need other demotion prevent mechanism to protect tmpfs pages. > Is split LRU enough? (I mean we consider tmpfs pages as anonymous > which is hard to reclaim than file backed pages). I think so. Split-LRU provide priotize anon rather than regular file. and old behavior is obvious strange. streaming io tolerance is one of fundamental VM requirement. So, I think current one is only historical reason. > > I don't mean to oppose this patch and I don't have a any number to > insist on my opinion. > Just what I want is that let's think about it more carefully and > listen other's opinions. :) > > Thanks for good suggestion. > > -- > Kind regards, > Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>