From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from haymarket.ed.ac.uk (haymarket.ed.ac.uk [129.215.128.53]) by kvack.org (8.8.7/8.8.7) with ESMTP id RAA07193 for ; Mon, 2 Mar 1998 17:37:43 -0500 Date: Mon, 2 Mar 1998 22:35:39 GMT Message-Id: <199803022235.WAA03546@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: Fairness in love and swapping In-Reply-To: References: <199802271941.TAA01151@dax.dcs.ed.ac.uk> Sender: owner-linux-mm@kvack.org To: Rik van Riel Cc: "Stephen C. Tweedie" , "Dr. Werner Fink" , torvalds@transmeta.com, nahshon@actcom.co.il, alan@lxorguk.ukuu.org.uk, paubert@iram.es, mingo@chiara.csoma.elte.hu, linux-mm@kvack.org List-ID: Hi, On Mon, 2 Mar 1998 17:19:41 +0100 (MET), Rik van Riel said: > Nevertheless, the system seems to run smoother when the > page-cache pages aren't thrown away immediately, but aged > as normal pages are. Read-ahead pages _are_ sometimes > freed before they're actually used, so in this case the > system _will_ have to read them again. Absolutely. The trouble is that a) the kernel likes to keep reclaiming pages from a single source if it is finding it easy to locate unused pages there, so when it starts on the page cache it _can_ get over zealous in reaping those pages; and b) starting to find free pages from swap is inherently difficult due to the initial age placed on pages. I rather suspect with those patches that it's not simply the aging of page cache pages which helps performance, but also the tuning of the balance between page cache and data page reclamation. --Stephen