From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 29 Jul 2002 03:37:12 -0400 (EDT) From: Vladimir Dergachev Reply-To: Vladimir Dergachev Subject: Re: [RFC] start_aggressive_readahead In-Reply-To: <3D44F01A.C7AAA1B4@zip.com.au> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: linux-mm@kvack.org List-ID: > > > - It shrinks the window size in response to "misses" - if > > > userspace requests a page which is *not* inside the previously-requested > > > window, the future window size is shrunk by 25% > > > > This one seems wierd. If I reference a page that could have been in a > > larger read-ahead window, shouldn't I make the window *larger* so that > > next time, it *will* be in the window? > > That's true. If the application is walking across a file > touching every fifth page, readahead will stabilise at > its minimum window size, which is less than five pages and > we lose bigtime. I'm not sure how to fix that while retaining > some sanity in the code. I am curious: which applications do you know of that actually do this ? What about growing the window even if there is a miss as long as misses are sequential and not further than a fixed amount from the window ? Vladimir Dergachev -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/