From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935148AbcKNRVX (ORCPT ); Mon, 14 Nov 2016 12:21:23 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:59780 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932174AbcKNRVV (ORCPT ); Mon, 14 Nov 2016 12:21:21 -0500 X-Originating-IP: 50.39.170.172 Date: Mon, 14 Nov 2016 09:21:10 -0800 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH tip/core/rcu 5/7] torture: Trace long read-side delays Message-ID: <20161114172110.yybjdk6p6754nlih@jtriplet-mobl2.jf.intel.com> References: <20161114165648.GA15216@linux.vnet.ibm.com> <1479142633-15315-5-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1479142633-15315-5-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: NeoMutt/20161104 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 14, 2016 at 08:57:11AM -0800, Paul E. McKenney wrote: > Although rcutorture will occasionally do a 50-millisecond grace-period > delay, these delays are quite rare. And rightly so, because otherwise > the read rate would be quite low. Thie means that it can be important > to identify whether or not a given run contained a long-delay read. > This commit therefore inserts a trace_rcu_torture_read() event to flag > runs containing long delays. > > Signed-off-by: Paul E. McKenney A couple of apparent typos below. With those fixed: Reviewed-by: Josh Triplett > include/trace/events/rcu.h | 5 ++++- > kernel/rcu/rcutorture.c | 11 ++++++++++- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h > index d3e756539d44..b31e05bc8e26 100644 > --- a/include/trace/events/rcu.h > +++ b/include/trace/events/rcu.h > @@ -698,7 +698,10 @@ TRACE_EVENT(rcu_batch_end, > /* > * Tracepoint for rcutorture readers. The first argument is the name > * of the RCU flavor from rcutorture's viewpoint and the second argument > - * is the callback address. > + * is the callback address. The third callback is the start time in > + * seconds, and the last two arguments are the grace period numbers > + * and the beginning and end of the read, respectively. Note that the > + * callback address can be NULL. s/third callback/third argument/? Also, s/and the beginning/of the beginning/? > TRACE_EVENT(rcu_torture_read, > > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c > index bf08fee53dc7..87c51225ceec 100644 > --- a/kernel/rcu/rcutorture.c > +++ b/kernel/rcu/rcutorture.c > @@ -289,15 +289,24 @@ static int rcu_torture_read_lock(void) __acquires(RCU) > > static void rcu_read_delay(struct torture_random_state *rrsp) > { > + unsigned long started; > + unsigned long completed; > const unsigned long shortdelay_us = 200; > const unsigned long longdelay_ms = 50; > + unsigned long long ts; > > /* We want a short delay sometimes to make a reader delay the grace > * period, and we want a long delay occasionally to trigger > * force_quiescent_state. */ > > - if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) > + if (!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { > + started = cur_ops->completed(); > + ts = rcu_trace_clock_local(); > mdelay(longdelay_ms); > + completed = cur_ops->completed(); > + do_trace_rcu_torture_read(cur_ops->name, NULL, ts, > + started, completed); > + } > if (!(torture_random(rrsp) % (nrealreaders * 2 * shortdelay_us))) > udelay(shortdelay_us); > #ifdef CONFIG_PREEMPT > -- > 2.5.2 >