From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 24 Oct 2000 18:16:31 -0600 From: "Jeff V. Merkey" Subject: Re: PATCH: killing read_ahead[] Message-ID: <20001024181631.B14069@vger.timpanogas.org> References: <39F5DAF5.1D3662BD@mandrakesoft.com> <20001025003049.E18138@nightmaster.csn.tu-chemnitz.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20001025003049.E18138@nightmaster.csn.tu-chemnitz.de>; from ingo.oeser@informatik.tu-chemnitz.de on Wed, Oct 25, 2000 at 12:30:49AM +0200 Sender: owner-linux-mm@kvack.org Return-Path: To: Ingo Oeser Cc: Linus Torvalds , Jeff Garzik , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wed, Oct 25, 2000 at 12:30:49AM +0200, Ingo Oeser wrote: > On Tue, Oct 24, 2000 at 12:46:36PM -0700, Linus Torvalds wrote: > > Actually, the _real_ answer is to make fs/block_dev.c use the page cache > > instead - and generic_file_read() does read-ahead that actually improves > > performance, unlike the silly contortions that the direct block-dev > > read-ahead tries to do. > > If we had a paper about the page cache this would be easy. > > In the beginning page cache was just previously mmaped pages, > that are clean and ready to be mapped again. > > Today we have them either dirty or clean, mapped or not(?), with and > without buffers, in highmem(?) or lowmem and everybody and its > children is using it for everything. > > We need a clear definition about (concurrent) states of page > cached pages, valid transitions (and locks/sema4s to take for > them), assumptions, guarantees etc. > > The only thing I see guaranteed, that every big thing to be > cached should live there and is page aligned and page sized. > > I'm trying hard to understand a concept in the page cache and to > get it's limits and guarantees, but still find it hard to get > them. > > Time for specs, I would say ;-) > > I could help to explain and formulate, if someone could only cut > the edges of how it works and what it will be. > > Thanks & Regards > > Ingo Oeser > -- > Feel the power of the penguin - run linux@your.pc > :x > - I hope we are not doing something stupid here, like breaking the f*!%cking page cache again. I've finaly got all the bugs out of NWFS on 2.4.0-test9, and have waded through the breakage of the past two testX releases of 2.4. Why do we need to disable read ahead on the page cache anyway? :-) Jeff > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > Please read the FAQ at http://www.tux.org/lkml/ -- 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.eu.org/Linux-MM/