Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752362AbaBZCxO (ORCPT ); Tue, 25 Feb 2014 21:53:14 -0500 Received: from mail-pa0-f45.google.com ([209.85.220.45]:41796 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751075AbaBZCxN (ORCPT ); Tue, 25 Feb 2014 21:53:13 -0500 Message-ID: <530D5715.1050901@mit.edu> Date: Tue, 25 Feb 2014 18:53:09 -0800 From: Andy Lutomirski User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Alexey Perevalov , linux-kernel@vger.kernel.org, tglx@linutronix.de, john.stultz@linaro.org CC: Anton Vorontsov , kyungmin.park@samsung.com, cw00.choi@samsung.com, akpm@linux-foundation.org, Anton Vorontsov Subject: Re: [PATCH v4 5/6] timerfd: Add support for deferrable timers References: <1392913425-29369-1-git-send-email-a.perevalov@samsung.com> <1392913425-29369-6-git-send-email-a.perevalov@samsung.com> In-Reply-To: <1392913425-29369-6-git-send-email-a.perevalov@samsung.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/20/2014 08:23 AM, Alexey Perevalov wrote: > From: Anton Vorontsov > > This patch implements a userland-side API for generic deferrable timers, > per linux/timer.h: > > * A deferrable timer will work normally when the system is busy, but > * will not cause a CPU to come out of idle just to service it; instead, > * the timer will be serviced when the CPU eventually wakes up with a > * subsequent non-deferrable timer. > > These timers are crucial for power saving, i.e. periodic tasks that want > to work in background when the system is under use, but don't want to > cause wakeups themselves. Please don't. This API sucks for all kinds of reasons: - Why is it a new kind of clock? - How deferrable is deferrable? - It adds new core code, which serves no purpose (the problem is already solved). On the other hand, if you added a fancier version of timerfd_settime that could explicitly set the slack value (or, equivalently, the earliest and latest allowable times), that could be quite useful. It's often bugged me that timer slack is per-process. --Andy -- 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/