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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 DC170C433E0 for ; Thu, 18 Jun 2020 22:27:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ACFD2207D8 for ; Thu, 18 Jun 2020 22:27:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592519245; bh=5LLHU83TJW662FBlQnZuvNz1/ymFXqtKCTV6ySPTQLE=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=1mvu+nWLZnvsCpt8wdfwbX7QI07NMdiWvQ1XPrlvYsR5iDEF3c88ICw/ftx/nUCBB aw11SaZ9Kbt8EV2xT64Ze41z1wH+R7SwylEDW0jbvJuboWP11DYyJKm0xgYBBRx3q6 zpT+iDA5jwpEZVNQ6rNqXueeoOzQU1iKuQMgDC1c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732287AbgFRW1X (ORCPT ); Thu, 18 Jun 2020 18:27:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:53630 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728597AbgFRW1W (ORCPT ); Thu, 18 Jun 2020 18:27:22 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E2E620732; Thu, 18 Jun 2020 22:27:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592519241; bh=5LLHU83TJW662FBlQnZuvNz1/ymFXqtKCTV6ySPTQLE=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=WlgqCujSPhVcnHCRV8QowhXtmrINgtijICinMfJNEQdcU1i3C6SPAjUK89r66cWlr TWmbzpI9tIK47gRj2sKxklr7rnmAFob5aKm5j2GQIU0OJ2dGJ7aQE07x17v8A5DBZI hM0WdWPZj4cFOrVBxtZRRUbeRa9FpW5bmeEedO0w= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 67DFC352264E; Thu, 18 Jun 2020 15:27:21 -0700 (PDT) Date: Thu, 18 Jun 2020 15:27:21 -0700 From: "Paul E. McKenney" To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, Davidlohr Bueso , Ingo Molnar , Josh Triplett , Lai Jiangshan , Marco Elver , Mathieu Desnoyers , rcu@vger.kernel.org, Steven Rostedt , "Uladzislau Rezki (Sony)" Subject: Re: [PATCH 5/7] rcu/trace: Use rsp's gp_seq in acceleration's rcu_grace_period tracepoint Message-ID: <20200618222721.GA2723@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200618202955.4024-1-joel@joelfernandes.org> <20200618202955.4024-5-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200618202955.4024-5-joel@joelfernandes.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 18, 2020 at 04:29:53PM -0400, Joel Fernandes (Google) wrote: > During acceleration of CB, the rsp's gp_seq is rcu_seq_snap'd. This is > the value used for acceleration - it is the value of gp_seq at which it > is safe the execute all callbacks in the callback list. > > The rdp's gp_seq is not very useful for this scenario. Make > rcu_grace_period report the rsp's gp_seq instead as it allows one to > reason about how the acceleration works. Good catch, but please instead trace the gp_seq_req local variable. Thanx, Paul > Signed-off-by: Joel Fernandes (Google) > --- > kernel/rcu/tree.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 81df1b837dd9d..c3bae7a83d792 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1437,9 +1437,9 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp) > > /* Trace depending on how much we were able to accelerate. */ > if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) > - trace_rcu_grace_period(rcu_state.name, "rdp", rdp->gp_seq, TPS("AccWaitCB")); > + trace_rcu_grace_period(rcu_state.name, "rsp", rcu_state.gp_seq, TPS("AccWaitCB")); > else > - trace_rcu_grace_period(rcu_state.name, "rdp", rdp->gp_seq, TPS("AccReadyCB")); > + trace_rcu_grace_period(rcu_state.name, "rsp", rcu_state.gp_seq, TPS("AccReadyCB")); > > /* Count CBs for tracing. */ > rcu_segcblist_countseq(&rdp->cblist, cbs, gps); > -- > 2.27.0.111.gc72c7da667-goog >