From owner-freebsd-stable@FreeBSD.ORG Thu Sep 1 03:23:02 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id DAC57106564A for ; Thu, 1 Sep 2011 03:23:01 +0000 (UTC) (envelope-from kob6558@gmail.com) Received: from mail-yi0-f54.google.com (mail-yi0-f54.google.com [209.85.218.54]) by mx1.freebsd.org (Postfix) with ESMTP id 5C5008FC15 for ; Thu, 1 Sep 2011 03:23:01 +0000 (UTC) Received: by yib19 with SMTP id 19so1432492yib.13 for ; Wed, 31 Aug 2011 20:23:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=g+kG+lNhQ/NpYMWj/6bztMGYTnIQN73uZQeLck7s/8E=; b=Plbavn9XSf1829aFzWnf+Clg55saleF0Q1IHPM0x0oyPFLsGKtoOyTpFQwLPHQ+pFK fNx2H2WXy2fkVJIaUk8tiMdpCvNdEVMpOfB/8Fksxw8TrOPr/c/zmQRFgMAN3TIidDpE wRjrkUSWES745cMvqzjmSh9LlwJKmCp0/lbfI= MIME-Version: 1.0 Received: by 10.150.74.7 with SMTP id w7mr984172yba.284.1314847380864; Wed, 31 Aug 2011 20:23:00 -0700 (PDT) Received: by 10.150.186.21 with HTTP; Wed, 31 Aug 2011 20:23:00 -0700 (PDT) In-Reply-To: <4e5f49fa.2qH1H6gV7TIdZYiD%perryh@pluto.rain.com> References: <4E5BF15F.9070601@es.net> <20110830214832.GA87354@icarus.home.lan> <20110830234323.GA88936@icarus.home.lan> <20110831071207.GA95960@icarus.home.lan> <4e5f49fa.2qH1H6gV7TIdZYiD%perryh@pluto.rain.com> Date: Wed, 31 Aug 2011 20:23:00 -0700 Message-ID: From: Kevin Oberman To: perryh@pluto.rain.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: dmagda@ee.ryerson.ca, freebsd-stable@freebsd.org, dart@es.net, freebsd@jdc.parodius.com Subject: Re: Unable to shutdown X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Sep 2011 03:23:02 -0000 On Thu, Sep 1, 2011 at 2:01 AM, wrote: > Jeremy Chadwick wrote: >> On Tue, Aug 30, 2011 at 11:04:43PM -0700, Kevin Oberman wrote: >> > ... the standrad does not specify EXACTLY what triggers a >> > transition from standby to ready (PM2 to PM0). Only that it is >> > something that requires media access. A write does not >> > necessarily require media access if you define "media" as the >> > disk platter. >> >> You're correct -- "media access" could mean, literally, "accessing >> the platter" OR it could mean "LBA read/write I/O". =A0Then comes >> into question whether or not the drive returning something from >> its on-board cache would count as "media access" or not. >> >> T13 should probably clarify on this point, and this is one I do >> not have an answer for myself. =A0I strongly believe "media access" >> means "LBA read/write I/O" and regardless if it's data that's in >> the on-board cache on the disk or not. =A0I wonder if this behaviour >> varies per drive model. > > Given a standard which is, shall we say, "open to interpretation", > I think the liklihood approaches 100% that it has been interpreted > differently by different manufacturers -- or even by different > firmware authors within a single manufacturer. =A0I would be amazed > if the behaviour did _not_ vary among drive models. And, if you tell your firmware writers that they should look for any technique that reduces power consumption, I don't doubt that keeping the disk in standby until there was a reason to move data from write cache to disk would look good. I would= hope that they would not make a cache flush lie, but that used to be common on old ATA drives. --=20 R. Kevin Oberman, Network Engineer - Retired E-mail: kob6558@gmail.com