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 SAA06198 for ; Mon, 16 Nov 1998 18:01:03 -0500 Date: Mon, 16 Nov 1998 21:48:35 +0100 (CET) From: Rik van Riel Reply-To: Rik van Riel Subject: Re: unexpected paging during large file reads in 2.1.127 In-Reply-To: <199811161959.TAA07259@dax.scot.redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: "Stephen C. Tweedie" Cc: Zlatko Calusic , "David J. Fred" , linux-kernel@vger.rutgers.edu, Linux-MM List List-ID: On Mon, 16 Nov 1998, Stephen C. Tweedie wrote: > On 12 Nov 1998 23:45:42 +0100, Zlatko Calusic > said: > > >> Agreed, we should do something about that. > >> > >> > + age_page(page); > >> > + age_page(page); > >> > age_page(page); > > The real cure is to disable page aging in the page cache completely. > Now that we have disabled it for swap, it makes absolutely no sense at > all to keep it in the page cache. This is not entirely true. There is a major difference between pages in the page cache and pages that can go into swap. The latter kind will always be mapped inside the address space of a program (where it gets proper aging and stuff), while file data could be used by doing a read() where the data never gets mapped into the processes address space. Now we can get severe problems with readahead when we are evicting just read-in data because it isn't mapped, resulting in us having to read it again and doing double I/O with a badly performing program. The only reason why it's better than the alternative is because we don't do swap readahead yet... cheers, Rik -- slowly getting used to dvorak kbd layout... +-------------------------------------------------------------------+ | 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