From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84284C433FF for ; Fri, 2 Aug 2019 17:21:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56D1121773 for ; Fri, 2 Aug 2019 17:21:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="EIUgStH2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404642AbfHBRVL (ORCPT ); Fri, 2 Aug 2019 13:21:11 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:34846 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404609AbfHBRVJ (ORCPT ); Fri, 2 Aug 2019 13:21:09 -0400 Received: by mail-wr1-f68.google.com with SMTP id y4so77956677wrm.2 for ; Fri, 02 Aug 2019 10:21:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=k7XXhuFhbeAXylvqHKe+SPxiEDLJJ/8J0ggCvzHZXcU=; b=EIUgStH2DoDr21rshDUNKpj6TBTjmp8CsMm0kFgYgmAY9rTMLbaBKjMgj/hwK8uKqb s8xhNITkdqAJluVpwDKBl0sJVtXBH6mf/DTp8MHACchcX6p5GyqtUGJ1WSLKBDuos+7G 0WBDCUcMuJdJ4JPrLSVKK+SQS8SSJl+Y8cMZP7FW2RfjOmMXHY65RPgmP/d2g3HcwQ8O aaMvnmVsE/Q6G7yH1QTqamGp7fCbLfqHcI9h84ac1LlfXx38KJb62Gkw9RXLUyb3cxXt UrHR5oZOQa42ryZLxbdXufbPgGnOGgohozxHXR5vm3d6ehe6E2EcG7wt7am2xaoaxOdy dgKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=k7XXhuFhbeAXylvqHKe+SPxiEDLJJ/8J0ggCvzHZXcU=; b=fPOAMIzwuCJHBVr/aj3ragdobTaywfVrNYaf3/1Uelu+OeVEv317YX8/v443vvaRon w1gyQkWMfFfBhkIhRLDO9ETsc/d/QQePQfaHPYmy0+eSsze1O5lVunCGrHTpHPUBweMg kkjyx2wb8EFC3xNKdMx5YfpX1K867ycI+F/Mjx7ZKCtOscDXMKnr4LJvhE6ROx4YrBEN fzodYg+sMbDzmPPrpZw/j1sxJVkAyjhDr5mxn3atNy7YAZ0HUXJeibI3Kwy77LzbXDfc JYiOsJKKcwXwPnaqyYqIYn14ZRznYEmFdSW2hSPHjJfxdS+Y/o2NC/ck1GdaWEgEt4AH XtJA== X-Gm-Message-State: APjAAAU6JHhVO+wBPl5le1uxy9PKkhrbesUM3u7r4ZskPHDyaq3sICES FF+lMAEvu1PtF31H/kvpSGs= X-Google-Smtp-Source: APXvYqzDP0EVG14dI+O6+H/eHBOJ6k1rlj1OHd5KX1DVwLlMZZW1ahk3gfVCGe+g53WZGSAhCo2WTQ== X-Received: by 2002:adf:e843:: with SMTP id d3mr2906477wrn.249.1564766466906; Fri, 02 Aug 2019 10:21:06 -0700 (PDT) Received: from google.com ([2a00:79e0:d:210:e751:37a0:1e95:e65d]) by smtp.gmail.com with ESMTPSA id f70sm104873631wme.22.2019.08.02.10.21.05 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 02 Aug 2019 10:21:06 -0700 (PDT) Date: Fri, 2 Aug 2019 18:21:04 +0100 From: Alessio Balsini To: Peter Zijlstra Cc: mingo@kernel.org, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, luca.abeni@santannapisa.it, bristot@redhat.com, dvyukov@google.com, tglx@linutronix.de, vpillai@digitalocean.com, rostedt@goodmis.org Subject: Re: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Message-ID: <20190802172104.GA134279@google.com> References: <20190726145409.947503076@infradead.org> <20190726161357.397880775@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190726161357.397880775@infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, This is indeed an important missing piece. I think it would be worth having some simple checks, e.g.: - period_min <= period_max; - period_min >= (1ULL << DL_SCALE). To be even more picky, I'm wondering if it would be a good practice to fail the write operation if there are already dl-tasks in the system that violate the new constraint. I'm afraid there is no cheap way of achieving such check, so, I think we can skip this last tricky thing for now. Thanks, Alessio On Fri, Jul 26, 2019 at 04:54:10PM +0200, Peter Zijlstra wrote: > > Cc: Daniel Bristot de Oliveira > Cc: Luca Abeni > Cc: Juri Lelli > Cc: Dmitry Vyukov > Signed-off-by: Peter Zijlstra (Intel) > --- > include/linux/sched/sysctl.h | 3 +++ > kernel/sched/deadline.c | 23 +++++++++++++++++++++-- > kernel/sysctl.c | 14 ++++++++++++++ > 3 files changed, 38 insertions(+), 2 deletions(-) > > --- a/include/linux/sched/sysctl.h > +++ b/include/linux/sched/sysctl.h > @@ -56,6 +56,9 @@ int sched_proc_update_handler(struct ctl > extern unsigned int sysctl_sched_rt_period; > extern int sysctl_sched_rt_runtime; > > +extern unsigned int sysctl_sched_dl_period_max; > +extern unsigned int sysctl_sched_dl_period_min; > + > #ifdef CONFIG_UCLAMP_TASK > extern unsigned int sysctl_sched_uclamp_util_min; > extern unsigned int sysctl_sched_uclamp_util_max; > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -2597,6 +2597,14 @@ void __getparam_dl(struct task_struct *p > } > > /* > + * Default limits for DL period; on the top end we guard against small util > + * tasks still getting rediculous long effective runtimes, on the bottom end we > + * guard against timer DoS. > + */ > +unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */ > +unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */ > + > +/* > * This function validates the new parameters of a -deadline task. > * We ask for the deadline not being zero, and greater or equal > * than the runtime, as well as the period of being zero or > @@ -2608,6 +2616,8 @@ void __getparam_dl(struct task_struct *p > */ > bool __checkparam_dl(const struct sched_attr *attr) > { > + u64 period, max, min; > + > /* special dl tasks don't actually use any parameter */ > if (attr->sched_flags & SCHED_FLAG_SUGOV) > return true; > @@ -2631,12 +2641,21 @@ bool __checkparam_dl(const struct sched_ > attr->sched_period & (1ULL << 63)) > return false; > > + period = attr->sched_period; > + if (!period) > + period = attr->sched_deadline; > + > /* runtime <= deadline <= period (if period != 0) */ > - if ((attr->sched_period != 0 && > - attr->sched_period < attr->sched_deadline) || > + if (period < attr->sched_deadline || > attr->sched_deadline < attr->sched_runtime) > return false; > > + max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC; > + min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC; > + > + if (period < min || period > max) > + return false; > + > return true; > } > > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -443,6 +443,20 @@ static struct ctl_table kern_table[] = { > .proc_handler = sched_rt_handler, > }, > { > + .procname = "sched_deadline_period_max_us", > + .data = &sysctl_sched_dl_period_max, > + .maxlen = sizeof(unsigned int), > + .mode = 0644, > + .proc_handler = proc_dointvec, > + }, > + { > + .procname = "sched_deadline_period_min_us", > + .data = &sysctl_sched_dl_period_min, > + .maxlen = sizeof(unsigned int), > + .mode = 0644, > + .proc_handler = proc_dointvec, > + }, > + { > .procname = "sched_rr_timeslice_ms", > .data = &sysctl_sched_rr_timeslice, > .maxlen = sizeof(int), > >