From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964949AbWD0GM2 (ORCPT ); Thu, 27 Apr 2006 02:12:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964951AbWD0GM2 (ORCPT ); Thu, 27 Apr 2006 02:12:28 -0400 Received: from smtp106.mail.mud.yahoo.com ([209.191.85.216]:40879 "HELO smtp106.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S964949AbWD0GM1 (ORCPT ); Thu, 27 Apr 2006 02:12:27 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=afGGgspXBXK4RDdnTCNtyKqExp54E7srcVUu/2pk3dxog67ZecdI7hEtn1c4iYj9XoG6x9S3FRfQ57hPO9Q/XhGJEJxbPphlB/+sAYZnbBwnBdezB3TpWUbRO3xRPwpar8lqT/fl7mqY+M7ZuzuMPt+BZjCjvYhz8IL/MAE9KMk= ; Message-ID: <44505D75.8070409@yahoo.com.au> Date: Thu, 27 Apr 2006 15:58:13 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Andrew Morton CC: Jens Axboe , linux-kernel@vger.kernel.org, npiggin@suse.de, linux-mm@kvack.org Subject: Re: Lockless page cache test results References: <20060426135310.GB5083@suse.de> <20060426095511.0cc7a3f9.akpm@osdl.org> <20060426174235.GC5002@suse.de> <20060426111054.2b4f1736.akpm@osdl.org> <20060426182323.GI5002@suse.de> <20060426114649.5a0e0dea.akpm@osdl.org> In-Reply-To: <20060426114649.5a0e0dea.akpm@osdl.org> 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 Andrew Morton wrote: > Jens Axboe wrote: > >>Are there cases where the lockless page cache performs worse than the >>current one? > > > Yeah - when human beings try to understand and maintain it. Have any tried yet? ;) I won't deny it is complex (because I don't like when I make the same point and people go on to take great trouble to convince me how simple it is!). But I hope it isn't _too_ bad. It is basically a dozen line function at the core, and that gets used to implement find_get_page, find_lock_page. Their semantics remain the same, so that's where the line is drawn (plus minor things, like an addition for reclaim's remove-from-pagecache protocol). IMO the rcu radix tree is probably the most complex bit... but that pales in comparison to things like our prio tree, or RCU trie. > > The usual tradeoffs apply ;) Definitely. It isn't fun if you just take the patch and merge it. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com