From mboxrd@z Thu Jan 1 00:00:00 1970 From: jalvo@mbay.net (John Alvord) Subject: Re: [PATCH] 2.2.17pre7 VM enhancement Re: I/O performance on 2.4.0-test2 Date: Wed, 12 Jul 2000 00:05:03 GMT Message-ID: <396bb43f.25232236@mail.mbay.net> References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: "Juan J. Quintela" , Rik van Riel , "Stephen C. Tweedie" , Marcelo Tosatti , Jens Axboe , Alan Cox , Derek Martin , Linux Kernel , linux-mm@kvack.org, "David S. Miller" List-ID: On Tue, 11 Jul 2000 21:32:30 +0200 (CEST), Andrea Arcangeli wrote: >On 11 Jul 2000, Juan J. Quintela wrote: > >>If you are copying in the background a cp and you don't touch your >>vi/emacs/whatever pages in 2 hours (i.e. age = 0) then I think that it >>is ok for that pages to be swaped out. Notice that the cage pages >>will have _initial age_ and the pages of the binaries will have an >>_older_ age. > >If we want to do that we can do that. My design doesn't forbid this. I >only avoid the overhead of the inactive list. > >Also note that what I was really complaining is to threat the lru_cached >and lru_mapped list equally. If you threat them equally you get in >troubles as I pointed out. I just want to say that lru_mapped have much >more priority than lru_cache. If you give the higher priority with a aging >factor, or I give higher priority with a different falling back behaviour >it doesn't matter (with the difference that I avoid overhead of refiling >between lru lists and I avoid to roll ex-mapped-pages in the lru_cache >list just to decrease their age). One question that puzzles me... cache for disk files and cache for program data will have very unlike characteristics. Executable program storage is typically more constant. Often disk files are read once and throw away and program data is often reused. This isn't always true, but it is very common. My puzzle is how the MM system should balance between those three uses of cache. Under pressure. it is very easy for disk file cache to overwhelm program data and executable storage. And equally program data can overwhelm disk file cache storage. If there is more than enough memory, no problem. When there is not enough, what algorithm is used to achieve an effective balance of usage? Thanks, John Alvord -- 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.eu.org/Linux-MM/