From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262555AbVF2LjK (ORCPT ); Wed, 29 Jun 2005 07:39:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262557AbVF2LjK (ORCPT ); Wed, 29 Jun 2005 07:39:10 -0400 Received: from smtp200.mail.sc5.yahoo.com ([216.136.130.125]:24170 "HELO smtp200.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S262555AbVF2Liv (ORCPT ); Wed, 29 Jun 2005 07:38:51 -0400 Message-ID: <42C28846.60702@yahoo.com.au> Date: Wed, 29 Jun 2005 21:38:46 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050324 Debian/1.7.6-1 X-Accept-Language: en MIME-Version: 1.0 To: Hirokazu Takahashi CC: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [rfc] lockless pagecache References: <42BF9CD1.2030102@yahoo.com.au> <20050629.194959.98866345.taka@valinux.co.jp> In-Reply-To: <20050629.194959.98866345.taka@valinux.co.jp> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hirokazu Takahashi wrote: > Hi Nick, > Hi, > Your patches improve the performance if lots of processes are > accessing the same file at the same time, right? > Yes. > If so, I think we can introduce multiple radix-trees instead, > which enhance each inode to be able to have two or more radix-trees > in it to avoid the race condition traversing the trees. > Some decision mechanism is needed which radix-tree each page > should be in, how many radix-tree should be prepared. > > It seems to be simple and effective. > > What do you think? > Sure it is a possibility. I don't think you could call it effective like a completely lockless version is effective. You might take more locks during gang lookups, you may have a lot of ugly and not-always-working heuristics (hey, my app goes really fast if it spreads accesses over a 1GB file, but falls on its face with a 10MB one). You might get increased cache footprints for common operations. I mainly did the patches for a bit of fun rather than to address a particular problem with a real workload and as such I won't be pushing to get them in the kernel for the time being. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com