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 FAA23916 for ; Mon, 6 Jul 1998 05:09:33 -0400 Date: Mon, 6 Jul 1998 08:41:03 +0200 (CEST) From: Rik van Riel Reply-To: Rik van Riel Subject: Re: increasing page size In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Gerard Roudier Cc: Peter-Paul Witta , Linux Kernel , Linux MM List-ID: On Sun, 5 Jul 1998, Gerard Roudier wrote: > On Sun, 5 Jul 1998, Rik van Riel wrote: > > > Even if files are fragmented, readahead _will_ give a large > > performance increase. This is because we can bring in the > > This requires: > > 1 - The program will really need the next page. > 2 - The latency to get the next page is far lower than the program > time execution before it will need of the next page. > 3 - The page is still in memory when the program will > need it. With good algorithms, the kernel can make some quite proper decisions on which readahead can be done and which readahead is too expensive... I believe Ingo's readahead code (not yet released) does something like this. It analizes the programs' usage pattern and swaps in until the page that has 50% probability of usage. If the program soft-faults one of the preread pages, the kernel reads in the next one(s) and this goes on until the kernel frees one of the preread pages. 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