Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756151AbZKSO0N (ORCPT ); Thu, 19 Nov 2009 09:26:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754776AbZKSO0M (ORCPT ); Thu, 19 Nov 2009 09:26:12 -0500 Received: from gv-out-0910.google.com ([216.239.58.188]:47184 "EHLO gv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754064AbZKSO0K (ORCPT ); Thu, 19 Nov 2009 09:26:10 -0500 MIME-Version: 1.0 In-Reply-To: <20091119141634.GA311@srcf.ucam.org> References: <20091118194053.GB12944@srcf.ucam.org> <20091118195342.GA13627@srcf.ucam.org> <20091118200712.GA14026@srcf.ucam.org> <20091118213355.GA16630@srcf.ucam.org> <20091119130107.GB20949@srcf.ucam.org> <20091119141634.GA311@srcf.ucam.org> From: Kay Sievers Date: Thu, 19 Nov 2009 15:25:59 +0100 Message-ID: Subject: Re: [PATCH] [RFC] Add support for uevents on block device idle changes To: Matthew Garrett Cc: David Zeuthen , linux-kernel@vger.kernel.org, axboe@kernel.dk, linux-hotplug@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1649 Lines: 33 On Thu, Nov 19, 2009 at 15:16, Matthew Garrett wrote: > On Thu, Nov 19, 2009 at 02:29:29PM +0100, Kay Sievers wrote: >> On Thu, Nov 19, 2009 at 14:01, Matthew Garrett wrote: >> > On Thu, Nov 19, 2009 at 12:09:30PM +0100, Kay Sievers wrote: >> >> On Wed, Nov 18, 2009 at 22:33, Matthew Garrett wrote: >> >> > My use cases are on the order of a second. >> >> >> >> Ok, what's the specific use case, which should be triggered after a >> >> second? I thought you were thinking about disk spindown or similar. >> > >> > The first is altering ALPM policy. ALPM will be initiated by the host if >> > the number of queued requests hits zero - if there's no hysteresis >> > implemented, then that can result in a significant performance hit. We >> > don't need /much/ hysteresis, but it's the difference between a 50% >> > performance hit and not having that. >> >> Can't that logic live entirely in the kernel, instead of being a >> rather generic userspace event interface (with the current limitation >> to a single user)? > > It could, but it seems a bit of a hack. It'd still also require the > timer to be in the kernel, so we might as well expose that to userspace. Sure, but a userspace configurable policy for an in-kernel disk-idle powermanagent sounds fine, compared to a single-subscriber userspace-only disk-idle event interface. :) Kay -- 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/