Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932473AbWEaGM0 (ORCPT ); Wed, 31 May 2006 02:12:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932482AbWEaGM0 (ORCPT ); Wed, 31 May 2006 02:12:26 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:42606 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S932473AbWEaGMZ (ORCPT ); Wed, 31 May 2006 02:12:25 -0400 Date: Wed, 31 May 2006 08:11:10 +0200 From: Jens Axboe To: Mark Lord Cc: Linus Torvalds , Nick Piggin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, mason@suse.com, andrea@suse.de, hugh@veritas.com Subject: Re: [rfc][patch] remove racy sync_page? Message-ID: <20060531061110.GB29535@suse.de> References: <447B8CE6.5000208@yahoo.com.au> <20060529183201.0e8173bc.akpm@osdl.org> <447BB3FD.1070707@yahoo.com.au> <447BD31E.7000503@yahoo.com.au> <447BD63D.2080900@yahoo.com.au> <447CE43A.6030700@yahoo.com.au> <447CF252.7010704@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <447CF252.7010704@rtr.ca> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1277 Lines: 30 On Tue, May 30 2006, Mark Lord wrote: > Linus wrote: > >(Yes, tagged queueing makes it less of an issue, of course. I know, > > My observations with (S)ATA tagged/native queuing, is that it doesn't make > nearly the difference under Linux that it does under other OSs. > Probably because our block layer is so good at ordering requests, > either from plugging or simply from clever disk scheduling. Hmm well, I have seen 30% performance increase for a random read work load with NCQ, I'd say that is pretty nice. And of course there's the whole write cache issue, with NCQ you _could_ get away with playing more safe and disabling write back caching. NCQ helps us with something we can never fix in software - the rotational latency. Ordering is only a small part of the picture. Plus I think that more recent drives have a better NCQ implementation, the first models I tried were pure and utter crap. Lets just say it didn't instill a lot of confidence in firmware engineers at various unnamed drive companies. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/