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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 BFBC9C433DF for ; Mon, 1 Jun 2020 09:53:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A45642077D for ; Mon, 1 Jun 2020 09:53:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726383AbgFAJwf (ORCPT ); Mon, 1 Jun 2020 05:52:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726022AbgFAJwZ (ORCPT ); Mon, 1 Jun 2020 05:52:25 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D48F0C08C5CA; Mon, 1 Jun 2020 02:52:24 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jfh7F-0003fb-KJ; Mon, 01 Jun 2020 11:52:21 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 5343C1C0481; Mon, 1 Jun 2020 11:52:21 +0200 (CEST) Date: Mon, 01 Jun 2020 09:52:21 -0000 From: "tip-bot2 for Peter Zijlstra" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] smp: Optimize flush_smp_call_function_queue() Cc: "Peter Zijlstra (Intel)" , Ingo Molnar , x86 , LKML In-Reply-To: <20200526161907.836818381@infradead.org> References: <20200526161907.836818381@infradead.org> MIME-Version: 1.0 Message-ID: <159100514119.17951.4934899720059285189.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 52103be07d8b08311955f8c30e535c2dda290cf4 Gitweb: https://git.kernel.org/tip/52103be07d8b08311955f8c30e535c2dda290cf4 Author: Peter Zijlstra AuthorDate: Tue, 26 May 2020 18:10:59 +02:00 Committer: Ingo Molnar CommitterDate: Thu, 28 May 2020 10:54:15 +02:00 smp: Optimize flush_smp_call_function_queue() The call_single_queue can contain (two) different callbacks, synchronous and asynchronous. The current interrupt handler runs them in-order, which means that remote CPUs that are waiting for their synchronous call can be delayed by running asynchronous callbacks. Rework the interrupt handler to first run the synchonous callbacks. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200526161907.836818381@infradead.org --- kernel/smp.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index 786092a..db2f738 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -209,9 +209,9 @@ void generic_smp_call_function_single_interrupt(void) */ static void flush_smp_call_function_queue(bool warn_cpu_offline) { - struct llist_head *head; - struct llist_node *entry; call_single_data_t *csd, *csd_next; + struct llist_node *entry, *prev; + struct llist_head *head; static bool warned; lockdep_assert_irqs_disabled(); @@ -235,21 +235,40 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline) csd->func); } + /* + * First; run all SYNC callbacks, people are waiting for us. + */ + prev = NULL; llist_for_each_entry_safe(csd, csd_next, entry, llist) { smp_call_func_t func = csd->func; void *info = csd->info; /* Do we wait until *after* callback? */ if (csd->flags & CSD_FLAG_SYNCHRONOUS) { + if (prev) { + prev->next = &csd_next->llist; + } else { + entry = &csd_next->llist; + } func(info); csd_unlock(csd); } else { - csd_unlock(csd); - func(info); + prev = &csd->llist; } } /* + * Second; run all !SYNC callbacks. + */ + llist_for_each_entry_safe(csd, csd_next, entry, llist) { + smp_call_func_t func = csd->func; + void *info = csd->info; + + csd_unlock(csd); + func(info); + } + + /* * Handle irq works queued remotely by irq_work_queue_on(). * Smp functions above are typically synchronous so they * better run first since some other CPUs may be busy waiting