From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752539Ab1CJI1Y (ORCPT ); Thu, 10 Mar 2011 03:27:24 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:44828 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752238Ab1CJI1W (ORCPT ); Thu, 10 Mar 2011 03:27:22 -0500 Date: Thu, 10 Mar 2011 00:25:34 -0800 From: Andrew Morton To: Scott James Remnant Cc: Alexander Shishkin , linux-kernel@vger.kernel.org, Ken MacLeod , Shaun Reich , Thomas Gleixner , Alexander Viro , Greg Kroah-Hartman , Feng Tang , Michael Tokarev , Marcelo Tosatti , John Stultz , Chris Friesen , Kay Sievers , "Kirill A. Shutemov" , Artem Bityutskiy , Davide Libenzi , linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, Michael Kerrisk Subject: Re: [RFCv4] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock changes Message-Id: <20110310002534.f984f8b2.akpm@linux-foundation.org> In-Reply-To: References: <1299681411-9227-1-git-send-email-virtuoso@slind.org> <20110309162513.5058c824.akpm@linux-foundation.org> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Mar 2011 18:01:09 -0800 Scott James Remnant wrote: > > It would be helpful to know if the identified users of this feature > > actually find it useful and adequate. __I guess the most common > > application is the 1,001 desktop clock widgets. __Do you have any > > feedback from any of the owners of those? > > > cron is another obvious one (or init systems attempting to replace > cron). Having to wakeup and check the time every minute can be > non-conducive to power savings, it would be better if we could just > sleep until the next alarm and be woken up if the time changes in > between. > > (That being said, we also need to poll for and/or check for timezone > changes - but those are entirely userspace, so we can deal with that > separately) Sure, there will be lots of applications. But what I'm asking isn't "it is a good feature". I'm asking "is the feature implemented well". Ideally someone would get down and modify cron to use the interface in this patch. That's a bit of work (although not a huge amount) and a compromise would be for app owners to sit down for half an hour and work through their code and the kernel interface and let us know whether they found the interface to be good and complete. Because it would be most regrettable if we were to roll this feature out and then three months later its users come back saying "what a shame you didn't do it *this* way". Also... Alexander, I assume you have a userspace test app? Please send it and we'll add it to the changelog for testers, as example code for implementers and as an additional way of reviewing the proposed interface. Thanks. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [RFCv4] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock changes Date: Thu, 10 Mar 2011 00:25:34 -0800 Message-ID: <20110310002534.f984f8b2.akpm@linux-foundation.org> References: <1299681411-9227-1-git-send-email-virtuoso@slind.org> <20110309162513.5058c824.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Alexander Shishkin , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Ken MacLeod , Shaun Reich , Thomas Gleixner , Alexander Viro , Greg Kroah-Hartman , Feng Tang , Michael Tokarev , Marcelo Tosatti , John Stultz , Chris Friesen , Kay Sievers , "Kirill A. Shutemov" , Artem Bityutskiy , Davide Libenzi , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Michael Kerrisk To: Scott James Remnant Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 9 Mar 2011 18:01:09 -0800 Scott James Remnant wrote: > > It would be helpful to know if the identified users of this feature > > actually find it useful and adequate. __I guess the most common > > application is the 1,001 desktop clock widgets. __Do you have any > > feedback from any of the owners of those? > > > cron is another obvious one (or init systems attempting to replace > cron). Having to wakeup and check the time every minute can be > non-conducive to power savings, it would be better if we could just > sleep until the next alarm and be woken up if the time changes in > between. > > (That being said, we also need to poll for and/or check for timezone > changes - but those are entirely userspace, so we can deal with that > separately) Sure, there will be lots of applications. But what I'm asking isn't "it is a good feature". I'm asking "is the feature implemented well". Ideally someone would get down and modify cron to use the interface in this patch. That's a bit of work (although not a huge amount) and a compromise would be for app owners to sit down for half an hour and work through their code and the kernel interface and let us know whether they found the interface to be good and complete. Because it would be most regrettable if we were to roll this feature out and then three months later its users come back saying "what a shame you didn't do it *this* way". Also... Alexander, I assume you have a userspace test app? Please send it and we'll add it to the changelog for testers, as example code for implementers and as an additional way of reviewing the proposed interface. Thanks.