From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268274AbUHXUaI (ORCPT ); Tue, 24 Aug 2004 16:30:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268276AbUHXUaI (ORCPT ); Tue, 24 Aug 2004 16:30:08 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:30638 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S268274AbUHXUaB (ORCPT ); Tue, 24 Aug 2004 16:30:01 -0400 Date: Tue, 24 Aug 2004 22:29:55 +0200 From: Jens Axboe To: Peter Osterlund Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Speed up the cdrw packet writing driver Message-ID: <20040824202951.GA24280@suse.de> References: <20040823114329.GI2301@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 23 2004, Peter Osterlund wrote: > Jens Axboe writes: > > > On Sat, Aug 14 2004, Peter Osterlund wrote: > > > Hi! > > > > > > This patch replaces the pd->bio_queue linked list with an rbtree. The > > > list can get very long (>200000 entries on a 1GB machine), so keeping > > > it sorted with a naive algorithm is far too expensive. > > > > It looks like you are assuming that bio->bi_sector is unique which isn't > > necessarily true. In that respect, list -> rbtree conversion isn't > > trivial (or, at least it requires extra code to handle this). > > I don't think that is assumed anywhere. > > The pkt_rbtree_find() function returns the first node with a sector > number >= s, even if there are multiple bios with bi_sector == s. Note > that the code branches to the left if s == tmp->bio->bi_sector. > > The pkt_rbtree_insert() function is careful to insert a bio after any > already existing bios with the same sector number. Note that it > branches to the right if s == tmp->bio->bi_sector. > > The tree rotations done internally in rbtree.c also can't mess things > up, because tree rotations don't change the inorder traversal order of > a tree. You are right, the code looks fine indeed. The bigger problem is probably that a faster data structure is needed at all, having hundreds of thousands bio's pending for a packet writing device is not nice at all. -- Jens Axboe