From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 8 Jul 1998 14:54:53 +0100 Message-Id: <199807081354.OAA03355@dax.dcs.ed.ac.uk> From: "Stephen C. Tweedie" MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: cp file /dev/zero <-> cache [was Re: increasing page size] In-Reply-To: References: Sender: owner-linux-mm@kvack.org To: "Benjamin C.R. LaHaise" Cc: Rik van Riel , "Stephen C. Tweedie" , Andrea Arcangeli , Linux MM , Linux Kernel List-ID: Hi, On Tue, 7 Jul 1998 13:32:34 -0400 (8UU), "Benjamin C.R. LaHaise" said: > This is the wrong fix for the case that Andrea is complaining about - > tossing out chunks of processes piecemeal, resulting in a length page-in > time when the process becomes active again. Two things that might help > with this are: read-ahead on swapins, and *true* swapping. I'm unconvinced. It's pretty clear that the underlying problem is that the cache is far too agressive when you are copying large amounts of data around. The fact that interactive performance is bad suggests not that the swapping algorithm is making bad decisions, but that it is being forced to work with far too little physical memory due to the cache size. There's no doubt that swap readahead and true full-process swapping can give us performance benefits, but Andrea is quite clearly seeing enormous resident cache sizes when copying large files to /dev/null, and that's a problem which we need to tackle independently of the swapper's own page selection algorithms. --Stephen -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org