From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 17 Nov 2008 08:37:56 -0800 (PST) From: Linus Torvalds Subject: Re: [PATCH] mm: evict streaming IO cache first In-Reply-To: Message-ID: References: <20081115181748.3410.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20081115210039.537f59f5.akpm@linux-foundation.org> <49208E9A.5080801@redhat.com> <20081116204720.1b8cbe18.akpm@linux-foundation.org> <20081117153012.51ece88f.kamezawa.hiroyu@jp.fujitsu.com> <2f11576a0811162239w58555c6dq8a61ec184b22bd52@mail.gmail.com> <20081117155417.5cc63907.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro , Andrew Morton , Rik van Riel , LKML , linux-mm , Gene Heskett List-ID: On Mon, 17 Nov 2008, Linus Torvalds wrote: > On Mon, 17 Nov 2008, KAMEZAWA Hiroyuki wrote: > > > > How about resetting zone->recent_scanned/rotated to be some value calculated from > > INACTIVE_ANON/INACTIVE_FILE at some time (when the system is enough idle) ? > > .. or how about just considering the act of adding a new page to the LRU > to be a "scan" event? IOW, "scanning" is not necessarily just an act of > the VM looking for pages to free, but would be a more general "activity" > meter. Another thing strikes me: it looks like the logic in "get_scan_ratio()" has a tendency to get unbalanced - if we end up deciding that we should scan a lot of anonymous pages, the scan numbers for anonymous pages will go up, and we get even _more_ eager to scan those. Of course, "rotate" events will then make us less likely again, but for streaming loads, you wouldn't expect to see those at all. There seems to be another bug there wrt the "aging" - we age anon page events and file page events independently, which sounds like it would make the math totally nonsensical. We do that whole anon / (anon + file) thing, but since anon and file counts are aged independently, that "math" is not math, it looks like a totally random number that has no meaning. So instead of having two independent aging things, if we age one side, we should age the other. No? But maybe I'm looking at it wrong. It doesn't seem sensible to me, but maybe there's some deeper truth in there somewhere that I'm missing.. Linus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org