From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752474AbeEOBBe (ORCPT ); Mon, 14 May 2018 21:01:34 -0400 Received: from mail-pg0-f67.google.com ([74.125.83.67]:42515 "EHLO mail-pg0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752139AbeEOBBc (ORCPT ); Mon, 14 May 2018 21:01:32 -0400 X-Google-Smtp-Source: AB8JxZpvXtSRoflr3BH4fkQYrqULSpfwonKK1JjvWyQJ/F31p9hwD6jnrNbyx3vpplZeweKD2Tb9sw== Date: Mon, 14 May 2018 18:01:31 -0700 From: Joel Fernandes To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , byungchul.park@lge.com, kernel-team@android.com Subject: Re: [PATCH RFC 7/8] rcu: trace CleanupMore condition only if needed Message-ID: <20180515010131.GF209519@joelaf.mtv.corp.google.com> References: <20180514031541.67247-1-joel@joelfernandes.org> <20180514031541.67247-8-joel@joelfernandes.org> <20180514192028.GG26088@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180514192028.GG26088@linux.vnet.ibm.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 14, 2018 at 12:20:28PM -0700, Paul E. McKenney wrote: > On Sun, May 13, 2018 at 08:15:40PM -0700, Joel Fernandes (Google) wrote: > > Currently the tree RCU clean up code records a CleanupMore trace event > > even if the GP was already in progress. This makes CleanupMore show up > > twice for no reason. Avoid it. > > > > Signed-off-by: Joel Fernandes (Google) > > Good catch, and I applied this patch. I did rework the commit log > a bit, so please look it over to make sure I didn't mess it up. > > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 52c4e689efd975f5383895b1bc1b91bc90fdd372 > Author: Joel Fernandes (Google) > Date: Sun May 13 20:15:40 2018 -0700 > > rcu: Produce last "CleanupMore" trace only if late-breaking request > > Currently the tree RCU clean-up code records a "CleanupMore" trace > event in response to late-arriving grace-period requests even if the > grace period was already requested. This makes "CleanupMore" show up an > extra time (in addition to once for each rcu_node structure that was > previously marked with the request) for no good reason. This commit > therefore avoids emitting this trace message unless the only if the only > request for this next grace period arrived during or after the cleanup > scan of the rcu_node structures. Yes, this is fine except "unless the only if the only" should be "unless the". thanks, - Joel > > Signed-off-by: Joel Fernandes (Google) > Signed-off-by: Paul E. McKenney > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 8063a0478870..de6447dd73de 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -2072,7 +2072,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) > rsp->gp_state = RCU_GP_IDLE; > /* Check for GP requests since above loop. */ > rdp = this_cpu_ptr(rsp->rda); > - if (ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) { > + if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) { > trace_rcu_this_gp(rnp, rdp, rnp->gp_seq_needed, > TPS("CleanupMore")); > needgp = true; >