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=-5.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 42F71C33C9E for ; Fri, 17 Jan 2020 22:18:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1191D21D56 for ; Fri, 17 Jan 2020 22:18:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="LfRx5pvZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726970AbgAQWSI (ORCPT ); Fri, 17 Jan 2020 17:18:08 -0500 Received: from mail-pf1-f196.google.com ([209.85.210.196]:33587 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726861AbgAQWSI (ORCPT ); Fri, 17 Jan 2020 17:18:08 -0500 Received: by mail-pf1-f196.google.com with SMTP id z16so12576050pfk.0 for ; Fri, 17 Jan 2020 14:18:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=apkoNmNueEmlW6DbknDEwDUk7paJjuboBqdPKRt5uKE=; b=LfRx5pvZwjleMwhu3r9sLni1dQV3OOv7jBLLHK9p5Wr5Bq3oeGJF7dfy13mJVVshc/ HtouQj9zyrAiSNGFoiql1YGNnUGKrV3j2B47NoGGv1HBdVWtMD+Gj9v9AttyIQI/JOWn vO34laggYffBHcbzOpDj0PBkKLr+LvAsYChgM= 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:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=apkoNmNueEmlW6DbknDEwDUk7paJjuboBqdPKRt5uKE=; b=n/hvsMLniYEwkUi2Q3/Bs2QSLykxG5IJx/CW7Q4uyD0r6oXGqnJ4dFEHtF4JkcxuPH 2zDTrirwGKW/EYJSNgwHypvQdf3Ab5ikmWx0qZgZ6hjGKbYEi1MA5C0CMYuzMyNVxbZC CLpz0X0ebDI9aKWBFv01uH+Q0d1XVNS6+gdZCEQJN84ExrKQ5LD6RqX1lPJ4r3UGXiGc IBMBlclzWivvs81xzMd7bRDLEOaBOYd0z9SOo0E7WBkIopDZSyx7nU8MRElhaqfNSB1v ynsePlro1RxYxpr5vgaen24MjisFl/x7gCdWCe6hAhGQijJti6kOjEwd9nTNxYclNbGb gnQw== X-Gm-Message-State: APjAAAWWBjU13iPmcwXf4kKb6jS2Dt6abME/2pP5XpwnptLKDjP3TxUM PTzrvCh2BcQr915WgQOBIK94t63hxGY= X-Google-Smtp-Source: APXvYqwIjHrNnIGY3KFBFxkV7T/YNv6TdLCbXtRxh6q0QTTX0ss8FQUFJbKXpqlXKe1AeD2SO1wybw== X-Received: by 2002:a62:158c:: with SMTP id 134mr5078321pfv.81.1579299486267; Fri, 17 Jan 2020 14:18:06 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id m19sm7434662pjv.10.2020.01.17.14.18.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jan 2020 14:18:05 -0800 (PST) Date: Fri, 17 Jan 2020 17:18:04 -0500 From: Joel Fernandes To: rcu@vger.kernel.org, paulmck@kernel.org, rostedt@goodmis.org, bristot@redhat.com Subject: Re: RCU_BOOST not working for me Message-ID: <20200117221804.GA211665@google.com> References: <20200117215814.GB206250@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200117215814.GB206250@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Fri, Jan 17, 2020 at 04:58:14PM -0500, Joel Fernandes wrote: > Hi, > Me and Daniel were poking around with RCU_BOOST. I wrote a kernel module to > test it a bit and I don't see the boost happening (thanks to Daniel for idea > of writing a module). Haven't debugged it more yet. Will look more tomorrow. > But below is the kernel module code and it prints a FAIL message to kernel > logs in a few seconds. > > I see the reader thread not getting CPU for several seconds. RCU_BOOST_DELAY > is set to 500. > > Thoughts? So this could be because I did not start a grace period which is quite silly. I am sorry about that. I will add another thread to start grace periods as well and let you know if I still see a problem. thanks, - Joel > > ---8<----------------------- > > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile > index c1860d35dc7e..ba34957dff26 100644 > --- a/drivers/misc/Makefile > +++ b/drivers/misc/Makefile > @@ -2,7 +2,7 @@ > # > # Makefile for misc devices that really don't fit anywhere else. > # > - > +obj-m += ptest.o > obj-$(CONFIG_IBM_ASM) += ibmasm/ > obj-$(CONFIG_IBMVMC) += ibmvmc.o > obj-$(CONFIG_AD525X_DPOT) += ad525x_dpot.o > diff --git a/drivers/misc/ptest.c b/drivers/misc/ptest.c > new file mode 100644 > index 000000000000..76cc9524ccac > --- /dev/null > +++ b/drivers/misc/ptest.c > @@ -0,0 +1,112 @@ > +#include > +#include > +#include > +#include > +#include > +#include > + > +#define RCU_READER_DELAY 100 //ms > +#define RCU_BLOCKER_DELAY 600 //ms > + > +MODULE_LICENSE("GPL"); > + > +struct sched_param { > + int sched_priority; > +}; > + > +int stop_test = 0; > +int test_pass = 1; > +int reader_exit = 0; > +s64 delta_fail; > + > +#define ns_to_ms(delta) (delta / 1000000ULL) > + > +static int rcu_reader(void *a) > +{ > + ktime_t start, end, reader_begin; > + s64 delta; > + > + reader_begin = ktime_get(); > + > + while (!kthread_should_stop() && !stop_test) { > + start = ktime_get(); > + rcu_read_lock(); > + trace_printk("rcu_reader entering RSCS\n"); > + mdelay(RCU_READER_DELAY); > + trace_printk("rcu_reader exiting RSCS\n"); > + rcu_read_lock(); > + end = ktime_get(); > + delta = ktime_to_ns(ktime_sub(end, start)); > + > + if (delta < 0 || (ns_to_ms(delta) > (2 * RCU_READER_DELAY))) { > + delta_fail = delta; > + test_pass = 0; > + break; > + } > + > + // Don't let the rcu_reader() run more than 3s inorder to > + // not starve the blocker incase reader prio > blocker prio. > + delta = ktime_to_ns(ktime_sub(end, reader_begin)); > + if (ns_to_ms(delta) > 3000) > + break; > + } > + > + stop_test = 1; > + reader_exit = 1; > + pr_err("Exiting reader\n"); > + return 0; > +} > + > +static int rcu_blocker(void *a) > +{ > + int loops = 5; > + > + while (!kthread_should_stop() && loops-- && !stop_test) { > + trace_printk("rcu_blocker entering\n"); > + mdelay(RCU_BLOCKER_DELAY); > + trace_printk("rcu_blocker exiting\n"); > + } > + > + pr_err("Exiting blocker\n"); > + stop_test = 1; > + > + // Wait for reader to finish > + while (!reader_exit) > + schedule_timeout_uninterruptible(1); > + > + if (test_pass) > + pr_err("TEST PASSED\n"); > + else > + pr_err("TEST FAILED, failing delta=%lldms\n", ns_to_ms(delta_fail)); > + > + return 0; > +} > + > +static int __init ptest_init(void){ > + struct sched_param params; > + struct task_struct *reader, *blocker; > + > + reader = kthread_create(rcu_reader, NULL, "reader"); > + params.sched_priority = 50; > + sched_setscheduler(reader, SCHED_FIFO, ¶ms); > + kthread_bind(reader, smp_processor_id()); > + > + blocker = kthread_create(rcu_blocker, NULL, "blocker"); > + params.sched_priority = 60; > + sched_setscheduler(blocker, SCHED_FIFO, ¶ms); > + kthread_bind(blocker, smp_processor_id()); > + > + wake_up_process(reader); > + > + // Let reader run a little > + mdelay(50); > + > + wake_up_process(blocker); > + return 0; > +} > + > +static void __exit ptest_exit(void){ > +} > + > +module_init(ptest_init); > +module_exit(ptest_exit); > -- > 2.25.0.341.g760bfbb309-goog >