From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: ahci: CAP_SSS and parallel scan Date: Fri, 07 May 2010 17:33:54 -0400 Message-ID: <4BE48742.8060604@garzik.org> References: <4BE27C49.5090809@kernel.org> <4BE28C4F.9000903@linux.intel.com> <4BE2D5D6.1010705@kernel.org> <4BE31D57.6020400@garzik.org> <4BE3A1A6.1040106@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-vw0-f46.google.com ([209.85.212.46]:60079 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756401Ab0EGVd6 (ORCPT ); Fri, 7 May 2010 17:33:58 -0400 Received: by vws3 with SMTP id 3so168368vws.19 for ; Fri, 07 May 2010 14:33:57 -0700 (PDT) In-Reply-To: <4BE3A1A6.1040106@kernel.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Arjan van de Ven , t.artem@mailcity.com, "linux-ide@vger.kernel.org" On 05/07/2010 01:14 AM, Tejun Heo wrote: > Hello, > > On 05/06/2010 09:49 PM, Jeff Garzik wrote: >> The problem being... that we are honoring SSS bit, and thus thing are >> slower? :) I don't see any reason to change that, seeing as how people >> may be using it to avoid power spikes. >> >> I agree there's no way to tell whether SSS is needed, but we cannot >> ignore SSS on that basis alone. We should avoid making the assumption >> that BIOS w/ SSS bit has already spun up all drives regardless. > > It's just that the usefulness seems very limited at this point so it > might be better idea to flip the default behavior and let people opt > in for SSS. The problem is compounded by the complete serial behavior > we end up with and on some machines large number of ahci ports. I > don't care much about boot time all that much but as that seems to be > a hot issue on desktops too these days. I'm not sure the usefulness is limited, as it definitely avoids power spikes on server BIOSen that care. Also, it seems unwise for the Linux SATA driver to do the exact -opposite- of what the SSS bit intends, by default. The existing ignore_sss option should be sufficient for people who wish to entertain non-standard behavior... Jeff