Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752695AbdLES3J (ORCPT ); Tue, 5 Dec 2017 13:29:09 -0500 Received: from mail-qt0-f193.google.com ([209.85.216.193]:39307 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752415AbdLES3F (ORCPT ); Tue, 5 Dec 2017 13:29:05 -0500 X-Google-Smtp-Source: AGs4zMajuWSyC1J7ghywRDjnOaOUpMS2inV1ymY1QI2Q5NU8Hsw2hku6KGXbyS2cggBCqGZplzUqpQ== Date: Tue, 5 Dec 2017 10:29:01 -0800 From: Tejun Heo To: "Michael Kerrisk (man-pages)" Cc: lkml , Lennart Poettering Subject: [PATCH v2 cgroup/for-4.15-fixes] cgroup: add warning about RT not being supported on cgroup2 Message-ID: <20171205182901.GW2421075@devbig577.frc2.facebook.com> References: <20171204214710.GM2421075@devbig577.frc2.facebook.com> <8fa060d2-07c7-7306-3d93-781c919f24eb@gmail.com> <20171205160049.GT2421075@devbig577.frc2.facebook.com> <20171205171357.GU2421075@devbig577.frc2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1336 Lines: 36 >From f0a821260f24ea9378ed0e0c149e3bbc1a1bd008 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 5 Dec 2017 09:10:17 -0800 We haven't yet figured out what to do with RT threads on cgroup2. Document the limitation. v2: Included the warning about system management software behavior as suggested by Michael. Signed-off-by: Tejun Heo Reported-by: "Michael Kerrisk (man-pages)" --- Documentation/cgroup-v2.txt | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index 779211f..c5e3c21 100644 --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -898,6 +898,13 @@ controller implements weight and absolute bandwidth limit models for normal scheduling policy and absolute bandwidth allocation model for realtime scheduling policy. +WARNING: cgroup2 doesn't yet support control of realtime processes and +the cpu controller can only be enabled when all RT processes are in +the root cgroup. Be aware that that system management software may +already have placed RT processes into nonroot cgroups during the +system boot process, and these processes may need to be moved to the +root cgroup before the cpu controller can be enabled. + CPU Interface Files ~~~~~~~~~~~~~~~~~~~ -- 2.9.5