From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 17 Nov 2008 09:06:07 -0800 (PST) From: Linus Torvalds Subject: Re: [PATCH] mm: evict streaming IO cache first In-Reply-To: <4921A1AF.1070909@redhat.com> 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> <4921A1AF.1070909@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: KAMEZAWA Hiroyuki , KOSAKI Motohiro , Andrew Morton , LKML , linux-mm , Gene Heskett List-ID: On Mon, 17 Nov 2008, Rik van Riel wrote: > Linus Torvalds wrote: > > > 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. > > True for streaming loads - if we scan the file list and find > mostly pages from streaming loads, we will become more eager > to scan the file list. The "count adding as activity" might hide that, but it does seem a big iffy. > > 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) > > That's an outdated comment. Andrew had a patch to update that > comment, but it must have gotten lost somewhere. I'll send you > a patch to update it. > > If you look at the actual calculation, you'l see that the > scan percentages are keyed off just swappiness and the > rotated/scanned ratios for each page category. Ok, that makes sense. Yes, as ratios the math looks valid. 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