On Tue, 23 Nov 2010 14:45:15 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > On Tue, Nov 23, 2010 at 2:22 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 23 Nov 2010 14:23:33 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > > > >> On Tue, Nov 23, 2010 at 2:01 PM, Andrew Morton > >> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > >> > On Tue, 23 Nov 2010 13:52:05 +0900 Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > >> > > >> >> >> +/* > >> >> >> + * Function used to forecefully demote a page to the head of the inactive > >> >> >> + * list. > >> >> >> + */ > >> >> > > >> >> > This comment is wrong? __The page gets moved to the _tail_ of the > >> >> > inactive list? > >> >> > >> >> No. I add it in _head_ of the inactive list intentionally. > >> >> Why I don't add it to _tail_ is that I don't want to be aggressive. > >> >> The page might be real working set. So I want to give a chance to > >> >> activate it again. > >> > > >> > Well.. __why? __The user just tried to toss the page away altogether. __If > >> > the kernel wasn't able to do that immediately, the best it can do is to > >> > toss the page away asap? > >> > > >> >> If it's not working set, it can be reclaimed easily and it can prevent > >> >> active page demotion since inactive list size would be big enough for > >> >> not calling shrink_active_list. > >> > > >> > What is "working set"? __Mapped and unmapped pagecache, or are you > >> > referring solely to mapped pagecache? > >> > >> I mean it's mapped by other processes. > >> > >> > > >> > If it's mapped pagecache then the user was being a bit silly (or didn't > >> > know that some other process had mapped the file). __In which case we > >> > need to decide what to do - leave the page alone, deactivate it, or > >> > half-deactivate it as this patch does. > >> > >> > >> What I want is the half-deactivate. > >> > >> Okay. We will use the result of invalidate_inode_page. > >> If fail happens by page_mapped, we can do half-deactivate. > >> But if fail happens by dirty(ex, writeback), we can add it to tail. > >> Does it make sense? > > > > Spose so. __It's unobvious. > > > > If the page is dirty or under writeback then reclaim will immediately > > move it to the head of the LRU anyway. __But given that the user has > > Why does it move into head of LRU? > If the page which isn't mapped doesn't have PG_referenced, it would be > reclaimed. If it's dirty or under writeback it can't be reclaimed! > > just freed a bunch of pages with invalidate(), it's unlikely that > > reclaim will be running soon. > > If reclaim doesn't start soon, it's good. That's because we have a > time to activate it and > when reclaim happens, reclaimer can reclaim pages easily. > > If I don't understand your point, could you elaborate on it? If reclaim doesn't happen soon and the page was dirty or under writeback (and hence unreclaimable) then there's a better chance that it _will_ be reclaimable by the time reclaim comes along and has a look at it. Yes, that's good. And a note to Mel: this is one way in which we can get significant (perhaps tremendous) numbers of dirty pages coming off the tail of the LRU, and hence eligible for pageout() treatment. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>