From patchwork Tue Mar 10 07:28:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?b?SsO8cmdlbiBHcm/Dnw==?= X-Patchwork-Id: 11428595 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 56EFD1800 for ; Tue, 10 Mar 2020 07:30:07 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3CFC324655 for ; Tue, 10 Mar 2020 07:30:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3CFC324655 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jBZK7-0001Z5-Le; Tue, 10 Mar 2020 07:29:07 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jBZK5-0001Yk-W9 for xen-devel@lists.xenproject.org; Tue, 10 Mar 2020 07:29:06 +0000 X-Inumbo-ID: cec9a1f4-62a0-11ea-8f6d-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id cec9a1f4-62a0-11ea-8f6d-bc764e2007e4; Tue, 10 Mar 2020 07:28:59 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 7CB11AC91; Tue, 10 Mar 2020 07:28:58 +0000 (UTC) From: Juergen Gross To: xen-devel@lists.xenproject.org Date: Tue, 10 Mar 2020 08:28:48 +0100 Message-Id: <20200310072853.27567-2-jgross@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200310072853.27567-1-jgross@suse.com> References: <20200310072853.27567-1-jgross@suse.com> Subject: [Xen-devel] [PATCH v4 1/6] xen/rcu: use rcu softirq for forcing quiescent state X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Juergen Gross , Stefano Stabellini , Julien Grall , Wei Liu , Andrew Cooper , Ian Jackson , George Dunlap , Jan Beulich MIME-Version: 1.0 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" As rcu callbacks are processed in __do_softirq() there is no need to use the scheduling softirq for forcing quiescent state. Any other softirq would do the job and the scheduling one is the most expensive. So use the already existing rcu softirq for that purpose. For telling apart why the rcu softirq was raised add a flag for the current usage. Signed-off-by: Juergen Gross Acked-by: Andrew Cooper --- xen/common/rcupdate.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c index d76b991627..03d84764d2 100644 --- a/xen/common/rcupdate.c +++ b/xen/common/rcupdate.c @@ -89,6 +89,8 @@ struct rcu_data { /* 3) idle CPUs handling */ struct timer idle_timer; bool idle_timer_active; + + bool process_callbacks; }; /* @@ -198,7 +200,7 @@ static void force_quiescent_state(struct rcu_data *rdp, struct rcu_ctrlblk *rcp) { cpumask_t cpumask; - raise_softirq(SCHEDULE_SOFTIRQ); + raise_softirq(RCU_SOFTIRQ); if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) { rdp->last_rs_qlen = rdp->qlen; /* @@ -206,7 +208,7 @@ static void force_quiescent_state(struct rcu_data *rdp, * rdp->cpu is the current cpu. */ cpumask_andnot(&cpumask, &rcp->cpumask, cpumask_of(rdp->cpu)); - cpumask_raise_softirq(&cpumask, SCHEDULE_SOFTIRQ); + cpumask_raise_softirq(&cpumask, RCU_SOFTIRQ); } } @@ -263,7 +265,10 @@ static void rcu_do_batch(struct rcu_data *rdp) if (!rdp->donelist) rdp->donetail = &rdp->donelist; else + { + rdp->process_callbacks = true; raise_softirq(RCU_SOFTIRQ); + } } /* @@ -414,7 +419,13 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, static void rcu_process_callbacks(void) { - __rcu_process_callbacks(&rcu_ctrlblk, &this_cpu(rcu_data)); + struct rcu_data *rdp = &this_cpu(rcu_data); + + if ( rdp->process_callbacks ) + { + rdp->process_callbacks = false; + __rcu_process_callbacks(&rcu_ctrlblk, rdp); + } } static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) @@ -522,6 +533,9 @@ static void rcu_idle_timer_handler(void* data) void rcu_check_callbacks(int cpu) { + struct rcu_data *rdp = &this_cpu(rcu_data); + + rdp->process_callbacks = true; raise_softirq(RCU_SOFTIRQ); }