From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-rt-users-owner@vger.kernel.org Received: from mail-wr1-f51.google.com ([209.85.221.51]:44907 "EHLO mail-wr1-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726010AbeHTMJK (ORCPT ); Mon, 20 Aug 2018 08:09:10 -0400 Received: by mail-wr1-f51.google.com with SMTP id r16-v6so12276205wrt.11 for ; Mon, 20 Aug 2018 01:54:24 -0700 (PDT) Date: Mon, 20 Aug 2018 10:54:20 +0200 From: Juri Lelli Subject: Re: SCHED_DEADLINE as user Message-ID: <20180820085420.GB8866@localhost.localdomain> References: <0ac9fabc-c316-2a59-c3dd-c7b4e4f93209@bristot.me> <20180817095106.GB27071@localhost.localdomain> <20180817102810.GC27071@localhost.localdomain> <513fd544-bc51-7ea6-8b94-983d28922a66@klingt.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <513fd544-bc51-7ea6-8b94-983d28922a66@klingt.org> Sender: linux-rt-users-owner@vger.kernel.org List-ID: To: Tim Blechmann Cc: Daniel Bristot de Oliveira , linux-rt-users@vger.kernel.org, Tommaso Cucinotta , Luca Abeni On 18/08/18 15:26, Tim Blechmann wrote: > >> audio applications typically use SCHED_FIFO. however they are > >> rate-monotonic by design, so i wanted to evaluate how SCHED_DEADLINE > >> behaves here. > > > > Right. Exactly what I started to think about lately as well. > > > >> > >>> Asking because we might want to have a look at how to relax the current > >>> privileges requirement. > >> > >> please :) > > > > Anything to try attracting new users. :-P > > > > More seriously, could you please describe in a bit more details your > > specific use case? Based on JACK I guess? Is it the application you are > > interested into public available somewhere? > > it could be based on JACK or natively on ALSA. furthermore the fun part > starts when trying to distribute work to multiple threads: during the > time slice of one audio callback (could be as low as 1.3ms), we need to > wake helper threads and (busy?)wait to collect all the results. (while > one of the applications is open source, it's not entirely > straight-forward to use) > > for me it's more an investigation if SCHED_DEADLINE is actually feasible > in real-world audio application these days. tommaso used to have a > research prototype [1], built directly into JACK. however currently i'd > be more interested in using it in ALSA. but yeah, it's more an > investigation as SCHED_FIFO does a decent job for my use case ... I (almost) see. Thanks for the details. > [1] http://retis.sssup.it/~tommaso/publications/LAC-2011.pdf So, this was IIRC using AQuoSA hierarchical RT on EDF scheduler implementation; which it was handy to easy the task of assigning CBS server parameters to JACK clients (graph). In your case - assuming you could already use DEADLINE for !root - do you think you would need to use the same interface for the multiple threads you are distributing work among? Or would you be fine with assigning runtime/deadline for each one of those? BTW, cc-ing Tommaso and Luca. Discussion started from https://www.spinics.net/lists/linux-rt-users/msg19296.html