From patchwork Thu May 11 16:45:19 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Bristot de Oliveira X-Patchwork-Id: 13238194 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A2E0C7EE22 for ; Thu, 11 May 2023 16:45:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238563AbjEKQpk (ORCPT ); Thu, 11 May 2023 12:45:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238514AbjEKQpi (ORCPT ); Thu, 11 May 2023 12:45:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F2BF7A80; Thu, 11 May 2023 09:45:31 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EF6D964FCB; Thu, 11 May 2023 16:45:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81725C433D2; Thu, 11 May 2023 16:45:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683823530; bh=rS/seoN1+7P2xQ2x2xDH3JwrwIf+ALD+zNBvOwN/k84=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gGhDrs0zKDL5WdeeRbee2+P+7nmNRUg8ffXzPlCkHBLiwrWi8Ef/1ImmmMN3i+Tzk /mqIQd/WRPYrRc+hlx0IE20R7Boi+00uyFv0B3BegteZhYsdxsyjIJwO5u/HmHj2sW PYhGtW8oCy6q6LSb25heIIG9641YZM9TOKuC9udHDWKZcLKbxvSyMlVsG+oJKJv1dV cmfKQ9I75PP4FPEogS7JGAEX7Ywg1UMSGD5z+IhCKxnwZot7AJ/dpB5Wv0QQr1kaLh 4Lf/s7NmNkqQYJzxxt1jss1ygysVhUsT/l3vjw+i/RKuDb2U+QYkVefQcXVCLBsAbK mwYcmqa6VRtxQ== From: Daniel Bristot de Oliveira To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Steven Rostedt Cc: Daniel Bristot de Oliveira , Juri Lelli , William White , Masami Hiramatsu Subject: [PATCH 1/2] tracing/osnoise: Switch from PF_NO_SETAFFINITY to migrate_disable Date: Thu, 11 May 2023 18:45:19 +0200 Message-Id: X-Mailer: git-send-email 2.38.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org Currently, osnoise/timerlat threads run with PF_NO_SETAFFINITY set. It works well, however, cgroups do not allow PF_NO_SETAFFINITY threads to be accepted, and this creates a limitation to osnoise/timerlat. To avoid this limitation, disable migration of the threads as soon as they start to run, and then clean the PF_NO_SETAFFINITY flag (still) used during thread creation. If for some reason a thread migration is requested, e.g., via sched_settafinity, the tracer thread will notice and exit. Cc: Steven Rostedt Cc: Daniel Bristot de Oliveira Cc: Masami Hiramatsu Signed-off-by: Daniel Bristot de Oliveira --- kernel/trace/trace_osnoise.c | 68 ++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index e97e3fa5cbed..c265ec5f1726 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -1545,6 +1545,39 @@ static void osnoise_sleep(void) } } +/* + * osnoise_migration_pending - checks if the task needs to migrate + * + * osnoise/timerlat threads are per-cpu. If there is a pending request to + * migrate the thread away from the current CPU, something bad has happened. + * Play the good citizen and leave. + * + * Returns 0 if it is safe to continue, 1 otherwise. + */ +static inline int osnoise_migration_pending(void) +{ + if (!current->migration_pending) + return 0; + + /* + * If migration is pending, there is a task waiting for the + * tracer to enable migration. The tracer does not allow migration, + * thus: taint and leave to unblock the blocked thread. + */ + osnoise_taint("migration requested to osnoise threads, leaving."); + + /* + * Unset this thread from the threads managed by the interface. + * The tracers are responsible for cleaning their env before + * exiting. + */ + mutex_lock(&interface_lock); + this_cpu_osn_var()->kthread = NULL; + mutex_unlock(&interface_lock); + + return 1; +} + /* * osnoise_main - The osnoise detection kernel thread * @@ -1553,12 +1586,29 @@ static void osnoise_sleep(void) */ static int osnoise_main(void *data) { + unsigned long flags; + + /* + * This thread was created pinned to the CPU using PF_NO_SETAFFINITY. + * The problem is that cgroup does not allow PF_NO_SETAFFINITY thread. + * + * To work around this limitation, disable migration and remove the + * flag. + */ + migrate_disable(); + raw_spin_lock_irqsave(¤t->pi_lock, flags); + current->flags &= ~(PF_NO_SETAFFINITY); + raw_spin_unlock_irqrestore(¤t->pi_lock, flags); while (!kthread_should_stop()) { + if (osnoise_migration_pending()) + break; + run_osnoise(); osnoise_sleep(); } + migrate_enable(); return 0; } @@ -1706,6 +1756,7 @@ static int timerlat_main(void *data) struct timerlat_variables *tlat = this_cpu_tmr_var(); struct timerlat_sample s; struct sched_param sp; + unsigned long flags; u64 now, diff; /* @@ -1714,6 +1765,18 @@ static int timerlat_main(void *data) sp.sched_priority = DEFAULT_TIMERLAT_PRIO; sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); + /* + * This thread was created pinned to the CPU using PF_NO_SETAFFINITY. + * The problem is that cgroup does not allow PF_NO_SETAFFINITY thread. + * + * To work around this limitation, disable migration and remove the + * flag. + */ + migrate_disable(); + raw_spin_lock_irqsave(¤t->pi_lock, flags); + current->flags &= ~(PF_NO_SETAFFINITY); + raw_spin_unlock_irqrestore(¤t->pi_lock, flags); + tlat->count = 0; tlat->tracing_thread = false; @@ -1731,6 +1794,7 @@ static int timerlat_main(void *data) osn_var->sampling = 1; while (!kthread_should_stop()) { + now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer)); diff = now - tlat->abs_period; @@ -1749,10 +1813,14 @@ static int timerlat_main(void *data) if (time_to_us(diff) >= osnoise_data.stop_tracing_total) osnoise_stop_tracing(); + if (osnoise_migration_pending()) + break; + wait_next_period(tlat); } hrtimer_cancel(&tlat->timer); + migrate_enable(); return 0; } #else /* CONFIG_TIMERLAT_TRACER */ From patchwork Thu May 11 16:45:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Bristot de Oliveira X-Patchwork-Id: 13238195 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 921F8C77B7C for ; Thu, 11 May 2023 16:45:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238312AbjEKQpl (ORCPT ); Thu, 11 May 2023 12:45:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58180 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238393AbjEKQpj (ORCPT ); Thu, 11 May 2023 12:45:39 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82D887DBC; Thu, 11 May 2023 09:45:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1F3B164FCE; Thu, 11 May 2023 16:45:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D379FC4339E; Thu, 11 May 2023 16:45:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683823532; bh=QN31lfcfV4O5vC4vDBplSjYRBUdS3kX3MOlPv3M48gA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qlWBJQzL3XbMbfNHEK7VwFmY+piyLj0vKqtx5D3w8PA1M74Sg+Q7yveaaxCmZii0l 8gEU22I8FauCQ0j+cnmMrfVCSA6A/k7EkImr8QgHbpaTIN6MU75D45JHWF5YmRggAN OzdxxczcXuMIPDuuWc0vpwPlTj8SHw0k6tayK6bfykq96TO7BPimV+iO7gd+W840eq +gDjtLmD4eofrvzT67REcg2TsMvoXg+Jv4nBXVn0/WjM0ZGghoCdcVW02UDrBGZw1z tvJSq+9wTO2VMeCJ+OVmguVdxxvPdC7zl2oyjFyiPlZHWpKofFFlKESSEWaBhKwFgi /Kn/i5cgrv38w== From: Daniel Bristot de Oliveira To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Steven Rostedt Cc: Daniel Bristot de Oliveira , Juri Lelli , William White , Masami Hiramatsu Subject: [PATCH 2/2] tracing/osnoise: Skip running osnoise if all instances are off Date: Thu, 11 May 2023 18:45:20 +0200 Message-Id: X-Mailer: git-send-email 2.38.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org In the case of all tracing instances being off, sleep for the entire period. Q: Why not kill all threads so? A: It is valid and useful to start the threads with tracing off. For example, rtla disables tracing, starts the tracer, applies the scheduling setup to the threads, e.g., sched priority and cgroup, and then begin tracing with all set. Skipping the period helps to speed up rtla setup and save the trace after a stop tracing. Cc: Steven Rostedt Cc: Daniel Bristot de Oliveira Cc: Masami Hiramatsu Signed-off-by: Daniel Bristot de Oliveira --- kernel/trace/trace_osnoise.c | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index c265ec5f1726..220172cb874d 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -1285,6 +1285,22 @@ static __always_inline void osnoise_stop_tracing(void) rcu_read_unlock(); } +/* + * osnoise_has_tracing_on - Check if there is at least one instance on + */ +static __always_inline int osnoise_has_tracing_on(void) +{ + struct osnoise_instance *inst; + int trace_is_on = 0; + + rcu_read_lock(); + list_for_each_entry_rcu(inst, &osnoise_instances, list) + trace_is_on += tracer_tracing_is_on(inst->tr); + rcu_read_unlock(); + + return trace_is_on; +} + /* * notify_new_max_latency - Notify a new max latency via fsnotify interface. */ @@ -1517,13 +1533,16 @@ static struct cpumask save_cpumask; /* * osnoise_sleep - sleep until the next period */ -static void osnoise_sleep(void) +static void osnoise_sleep(bool skip_period) { u64 interval; ktime_t wake_time; mutex_lock(&interface_lock); - interval = osnoise_data.sample_period - osnoise_data.sample_runtime; + if (skip_period) + interval = osnoise_data.sample_period; + else + interval = osnoise_data.sample_period - osnoise_data.sample_runtime; mutex_unlock(&interface_lock); /* @@ -1604,8 +1623,14 @@ static int osnoise_main(void *data) if (osnoise_migration_pending()) break; + /* skip a period if tracing is off on all instances */ + if (!osnoise_has_tracing_on()) { + osnoise_sleep(true); + continue; + } + run_osnoise(); - osnoise_sleep(); + osnoise_sleep(false); } migrate_enable();