Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261748AbUDCNto (ORCPT ); Sat, 3 Apr 2004 08:49:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261746AbUDCNto (ORCPT ); Sat, 3 Apr 2004 08:49:44 -0500 Received: from mail.shareable.org ([81.29.64.88]:45718 "EHLO mail.shareable.org") by vger.kernel.org with ESMTP id S261748AbUDCNtf (ORCPT ); Sat, 3 Apr 2004 08:49:35 -0500 Date: Sat, 3 Apr 2004 14:49:14 +0100 From: Jamie Lokier To: Jeremy Higdon Cc: Jeff Garzik , Nick Piggin , linux-ide@vger.kernel.org, Linux Kernel , Andrew Morton Subject: Re: [PATCH] speed up SATA Message-ID: <20040403134914.GC4706@mail.shareable.org> References: <406611CA.3050804@pobox.com> <406616EE.80301@pobox.com> <4066191E.4040702@yahoo.com.au> <40662108.40705@pobox.com> <20040328135124.GA32597@mail.shareable.org> <40670A36.3000005@pobox.com> <20040328173623.GA1087@mail.shareable.org> <20040402101108.GA752170@sgi.com> <20040402161149.GA32483@mail.shareable.org> <20040403104826.GA737325@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040403104826.GA737325@sgi.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1304 Lines: 30 Jeremy Higdon wrote: > > Are you refuting the following assertion by Eric D. Mudama's, based on > > your measurements? In other words, are ATA's 32 TCQ slots enough to > > eliminate the performance advantage of write cacheing? > > I must apologize. I had thought the context was SCSI, but now I > see that it is linux-ide. So please disregard comments about command > queueing. We're talking about _with_ TCQ, on serial ATA (SATA) where TCQ is common, and deliberately disabling the write cache so that TCQ completions indicate when the data is written. If your measurements indicate that 32 queue slots is adequate with SCSI drives to eliminate the overhead of disabling write cacheing, then that's valuable information. The drives are basically the same after all. > If you have write cache disabled and no TCQ (latter is common, > former may or may not be), you want to write as big a chunk as you can. That's a handy insight too. Personally I hadn't thought about large requests reducing the rotation latency with write cache disabled. -- Jamie - 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/