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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 46214C4338F for ; Fri, 30 Jul 2021 14:22:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3147C60F9B for ; Fri, 30 Jul 2021 14:22:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239526AbhG3OW6 (ORCPT ); Fri, 30 Jul 2021 10:22:58 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:56212 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239271AbhG3OSZ (ORCPT ); Fri, 30 Jul 2021 10:18:25 -0400 Message-ID: <20210730135208.691612668@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1627654699; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=EMwGRcY8RvXr6JjSs+RtaU5AQSasgUEmDuYASR2ZIq8=; b=BWkax6fvdyZkTTkt2qFBSymvsbsAip3g6LbRKAObsOrKmvAYulR0+KWjSuP6oStf3k5QAG N2bPV7sLYut6qRuhEOJHAamgWx8RwDWAS69wKpKuD/zwvf1QG7A+ujC3Bf3LfvEod2mn8+ ZXvWLlshk0Un/iivL/urQ+i0d+jL46weCyN2g37TL/WP1H8EuPyLJs79gxJUHMIt+Cde6r 5pRS/omIolc7UYXcmapggxpd19V2RiOyR2rXWodDVGXcwLFYnOeHQPgGZ5LFdscerfCcYh IHSNoYdjvnIAgnkql7uT67Z5P6YHgyFKsS8yYMmzpw/6HhwQ0SnT+Wu604tRTA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1627654699; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: references:references; bh=EMwGRcY8RvXr6JjSs+RtaU5AQSasgUEmDuYASR2ZIq8=; b=LckeqWr9LUrLBhUFlaXTuKwF6y7YIyn+Bv6mR3j1YAZTv+80ZzO5NEL1ad2juHpcyyScmY 9D2kw5nyYRdUFNDg== Date: Fri, 30 Jul 2021 15:51:10 +0200 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Ingo Molnar , Juri Lelli , Steven Rostedt , Daniel Bristot de Oliveira , Will Deacon , Waiman Long , Boqun Feng , Sebastian Andrzej Siewior , Davidlohr Bueso Subject: [patch 63/63] locking/rtmutex: Use adaptive spinwait for all rtmutex based locks References: <20210730135007.155909613@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is no reason to restrict adaptive spinwait to the rt mutex based 'spinlocks'. Testing on RT shows a 4x impromevemt for hackbench. Signed-off-by: Thomas Gleixner --- --- kernel/locking/rtmutex.c | 84 +++++++++++++++++++++++++---------------------- 1 file changed, 45 insertions(+), 39 deletions(-) --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1277,6 +1277,43 @@ static __always_inline void __rt_mutex_u rt_mutex_slowunlock(lock); } +#ifdef CONFIG_SMP +/* + * Note that owner is a speculative pointer and dereferencing relies + * on rcu_read_lock() and the check against the lock owner. + */ +static bool rtmutex_adaptive_spinwait(struct rt_mutex_base *lock, + struct task_struct *owner) +{ + bool res = true; + + rcu_read_lock(); + for (;;) { + /* Owner changed. Trylock again */ + if (owner != rt_mutex_owner(lock)) + break; + /* + * Ensure that owner->on_cpu is dereferenced _after_ + * checking the above to be valid. + */ + barrier(); + if (!owner->on_cpu) { + res = false; + break; + } + cpu_relax(); + } + rcu_read_unlock(); + return res; +} +#else +static bool rtmutex_adaptive_spinwait(struct rt_mutex_base *lock, + struct task_struct *owner) +{ + return false; +} +#endif + #ifdef RT_MUTEX_BUILD_MUTEX /* * Functions required for: @@ -1361,6 +1398,7 @@ static int __sched rt_mutex_slowlock_blo struct rt_mutex_waiter *waiter) { struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex); + struct task_struct *owner; int ret = 0; for (;;) { @@ -1383,9 +1421,14 @@ static int __sched rt_mutex_slowlock_blo break; } + if (waiter == rt_mutex_top_waiter(lock)) + owner = rt_mutex_owner(lock); + else + owner = NULL; raw_spin_unlock_irq(&lock->wait_lock); - schedule(); + if (!owner || !rtmutex_adaptive_spinwait(lock, owner)) + schedule(); raw_spin_lock_irq(&lock->wait_lock); set_current_state(state); @@ -1534,43 +1577,6 @@ static __always_inline int __rt_mutex_lo * Functions required for spin/rw_lock substitution on RT kernels */ -#ifdef CONFIG_SMP -/* - * Note that owner is a speculative pointer and dereferencing relies - * on rcu_read_lock() and the check against the lock owner. - */ -static bool rtlock_adaptive_spinwait(struct rt_mutex_base *lock, - struct task_struct *owner) -{ - bool res = true; - - rcu_read_lock(); - for (;;) { - /* Owner changed. Trylock again */ - if (owner != rt_mutex_owner(lock)) - break; - /* - * Ensure that owner->on_cpu is dereferenced _after_ - * checking the above to be valid. - */ - barrier(); - if (!owner->on_cpu) { - res = false; - break; - } - cpu_relax(); - } - rcu_read_unlock(); - return res; -} -#else -static bool rtlock_adaptive_spinwait(struct rt_mutex_base *lock, - struct task_struct *owner) -{ - return false; -} -#endif - /** * rtlock_slowlock_locked - Slow path lock acquisition for RT locks * @lock: The underlying rt mutex @@ -1603,7 +1609,7 @@ static void __sched rtlock_slowlock_lock owner = NULL; raw_spin_unlock_irq(&lock->wait_lock); - if (!owner || !rtlock_adaptive_spinwait(lock, owner)) + if (!owner || !rtmutex_adaptive_spinwait(lock, owner)) schedule_rtlock(); raw_spin_lock_irq(&lock->wait_lock);