From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from max.phys.uu.nl (max.phys.uu.nl [131.211.32.73]) by kvack.org (8.8.7/8.8.7) with ESMTP id SAA14799 for ; Fri, 24 Jul 1998 18:12:58 -0400 Date: Fri, 24 Jul 1998 23:55:10 +0200 (CEST) From: Rik van Riel Reply-To: Rik van Riel Subject: Re: More info: 2.1.108 page cache performance on low memory In-Reply-To: <87ww93dvyt.fsf@atlas.CARNet.hr> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Zlatko Calusic Cc: "Stephen C. Tweedie" , "Eric W. Biederman" , Linux MM List-ID: On 24 Jul 1998, Zlatko Calusic wrote: > > There's also a 'soft limit', or borrow percentage. Ultimately > > the minimum and maximum percentages should be 0 and 100 % > > respectively. > > Could you elaborate on "borrow" percentage? I have some trouble > understanding what that could be. It's an idea I stole from Digital Unix :) Basically, the cache is allowed to grow boundless, but is reclaimed until it reaches the borrow percentage when memory is short. The philosophy behind is that caching the disk doesn't make much sense beyond a certain point. It's a primitive idea, but it seems to have saved Andrea's machine quite well (with the additional patch). I admit your patch (multiple aging) should work even better, but in order to do that, we probably want to make it auto-tuning on the borrow percentage: - if page_cache_size > borrow + 5% --> add aging loop - if loads_of_disk_io and almost thrashing [*] --> remove aging loop [*] this thrashing can be measured by testing the cache hit/mis rate; if it falls below (say) 50% we could consider thrashing. (50% should be a good rate for an aging cache, and the amount of loops is trimmed quickly enough when we grow anyway. This mechanism could make a nice somewhat adjusting trimming mechanism. Expect a patch soon...) Rik. +-------------------------------------------------------------------+ | Linux memory management tour guide. H.H.vanRiel@phys.uu.nl | | Scouting Vries cubscout leader. http://www.phys.uu.nl/~riel/ | +-------------------------------------------------------------------+ -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org