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From: Joel Fernandes <joel@joelfernandes.org>
To: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org, max.byungchul.park@gmail.com,
	byungchul.park@lge.com, Davidlohr Bueso <dave@stgolabs.net>,
	Josh Triplett <josh@joshtriplett.org>,
	kernel-team@android.com, kernel-team@lge.com,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Rao Shoaib <rao.shoaib@oracle.com>,
	rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH RFC v1 2/2] rcuperf: Add kfree_rcu performance Tests
Date: Fri, 9 Aug 2019 12:01:55 -0400	[thread overview]
Message-ID: <20190809160155.GA221383@google.com> (raw)
In-Reply-To: <20190807175657.GF28441@linux.ibm.com>

On Wed, Aug 07, 2019 at 10:56:57AM -0700, Paul E. McKenney wrote:
> On Wed, Aug 07, 2019 at 06:22:13AM -0400, Joel Fernandes wrote:
> > On Tue, Aug 06, 2019 at 05:29:15PM -0700, Paul E. McKenney wrote:
> > > On Tue, Aug 06, 2019 at 05:20:41PM -0400, Joel Fernandes (Google) wrote:
> > > > This test runs kfree_rcu in a loop to measure performance of the new
> > > > kfree_rcu, with and without patch.
> > > > 
> > > > To see improvement, run with boot parameters:
> > > > rcuperf.kfree_loops=2000 rcuperf.kfree_alloc_num=100 rcuperf.perf_type=kfree
> > > > 
> > > > Without patch, test runs in 6.9 seconds.
> > > > With patch, test runs in 6.1 seconds (+13% improvement)
> > > > 
> > > > If it is desired to run the test but with the traditional (non-batched)
> > > > kfree_rcu, for example to compare results, then you could pass along the
> > > > rcuperf.kfree_no_batch=1 boot parameter.
> > > 
> > > You lost me on this one.  You ran two runs, with rcuperf.kfree_no_batch=1
> > > and without?  Or you ran this patch both with and without the earlier
> > > patch, and could have run with the patch and rcuperf.kfree_no_batch=1?
> > 
> > I always run the rcutorture test with patch because the patch doesn't really
> > do anything if rcuperf.kfree_no_batch=0. This parameter is added so that in
> > the future folks can compare effect of non-batching with that of the
> > batching. However, I can also remove the patch itself and run this test
> > again.
> > 
> > > If the latter, it would be good to try all three.
> > 
> > Ok, sure.
> 
> Very good!  And please make the commit log more clear.  ;-)

Sure will do :)

> > > > +	long me = (long)arg;
> > > > +	struct kfree_obj **alloc_ptrs;
> > > > +	u64 start_time, end_time;
> > > > +
> > > > +	VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
> > > > +	set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
> > > > +	set_user_nice(current, MAX_NICE);
> > > > +	atomic_inc(&n_kfree_perf_thread_started);
> > > > +
> > > > +	alloc_ptrs = (struct kfree_obj **)kmalloc(sizeof(struct kfree_obj *) * kfree_alloc_num,
> > > > +						  GFP_KERNEL);
> > > > +	if (!alloc_ptrs)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	start_time = ktime_get_mono_fast_ns();
> > > 
> > > Don't you want to announce that you started here rather than above in
> > > order to avoid (admittedly slight) measurement inaccuracies?
> > 
> > I did not follow, are you referring to the measurement inaccuracy related to
> > the "kfree_perf_thread task started" string print?  Or, are you saying that
> > ktime_get_mono_fast_ns() has to start earlier than over here?
> 
> I am referring to the atomic_inc().

Oh yes, great catch. I will increment closer to the test's actual start.
thanks!

> > (I will reply to the rest of the comments below in a bit, I am going to a
> > hospital now to visit a sick relative and will be back a bit later.)
> 
> Ouch!!!  I hope that goes as well as it possibly can!  And please don't
> neglect your relative on RCU's account!!!

Thanks! it went quite well and now I am back to work ;-)

 - Joel


  reply	other threads:[~2019-08-09 16:01 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-06 21:20 [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree_rcu batching Joel Fernandes (Google)
2019-08-06 21:20 ` [PATCH RFC v1 2/2] rcuperf: Add kfree_rcu performance Tests Joel Fernandes (Google)
2019-08-07  0:29   ` Paul E. McKenney
2019-08-07 10:22     ` Joel Fernandes
2019-08-07 17:56       ` Paul E. McKenney
2019-08-09 16:01         ` Joel Fernandes [this message]
2019-08-11  2:01     ` Joel Fernandes
2019-08-11 23:42       ` Paul E. McKenney
2019-08-06 23:56 ` [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree_rcu batching Paul E. McKenney
2019-08-07  9:45   ` Joel Fernandes
2019-08-07 17:52     ` Paul E. McKenney
2019-08-08  9:52       ` Byungchul Park
2019-08-08 12:56         ` Joel Fernandes
2019-08-08 14:23           ` Byungchul Park
2019-08-08 18:09             ` Paul E. McKenney
2019-08-11  8:36               ` Byungchul Park
2019-08-11  8:49                 ` Byungchul Park
2019-08-11 23:49                   ` Paul E. McKenney
2019-08-12 10:10                     ` Byungchul Park
2019-08-12 13:12                       ` Joel Fernandes
2019-08-13  5:29                         ` Byungchul Park
2019-08-13 15:41                           ` Paul E. McKenney
2019-08-14  0:11                             ` Byungchul Park
2019-08-14  2:53                               ` Paul E. McKenney
2019-08-14  3:43                                 ` Byungchul Park
2019-08-14 16:59                                   ` Paul E. McKenney
2019-08-11 10:37                 ` Byungchul Park
2019-08-08 23:30           ` Joel Fernandes
2019-08-09 15:16             ` Paul E. McKenney
2019-08-09 15:39               ` Joel Fernandes
2019-08-09 16:33                 ` Paul E. McKenney
2019-08-09 20:22                   ` Joel Fernandes
2019-08-09 20:26                     ` Joel Fernandes
2019-08-09 21:25                       ` Joel Fernandes
2019-08-10  3:38                         ` Paul E. McKenney
2019-08-09 20:29                     ` Joel Fernandes
2019-08-09 20:42                     ` Paul E. McKenney
2019-08-09 21:36                       ` Joel Fernandes
2019-08-10  3:40                         ` Paul E. McKenney
2019-08-10  3:52                           ` Joel Fernandes
2019-08-10  2:42       ` Joel Fernandes
2019-08-10  3:38         ` Paul E. McKenney
2019-08-10  4:20           ` Joel Fernandes
2019-08-10 18:24             ` Paul E. McKenney
2019-08-11  2:26               ` Joel Fernandes
2019-08-11 23:35                 ` Paul E. McKenney
2019-08-12 13:13                   ` Joel Fernandes
2019-08-12 14:44                     ` Paul E. McKenney
2019-08-08 10:26     ` Byungchul Park
2019-08-08 18:11       ` Paul E. McKenney
2019-08-08 20:13         ` Joel Fernandes
2019-08-08 20:51           ` Paul E. McKenney
2019-08-08 22:34             ` Joel Fernandes
2019-08-08 22:37               ` Paul E. McKenney

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