linux-kernel - Re: [PATCH v2 rcu-dev 1/3] rcuperf: Add ability to increase object allocation size

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Date:   Tue, 17 Mar 2020 14:45:02 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        rcu@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        urezki@...il.com
Subject: Re: [PATCH v2 rcu-dev 1/3] rcuperf: Add ability to increase object
 allocation size

On Tue, Mar 17, 2020 at 02:08:22PM -0700, Paul E. McKenney wrote:
> On Mon, Mar 16, 2020 at 12:32:26PM -0400, Joel Fernandes (Google) wrote:
> > This allows us to increase memory pressure dynamically using a new
> > rcuperf boot command line parameter called 'rcumult'.
> > 
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> 
> Applied for testing and review, thank you!

But testing did not go far:

kernel/rcu/tree.c: In function ‘kfree_rcu_shrink_count’:
kernel/rcu/tree.c:3120:16: warning: unused variable ‘flags’ [-Wunused-variable]
  unsigned long flags, count = 0;
                ^~~~~

I will drop these and await a replacement.

							Thanx, Paul

> > ---
> > 
> > The Series v1->v2 only has added a new patch (3/3).
> > 
> > 
> >  kernel/rcu/rcuperf.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
> > index a4a8d097d84d9..16dd1e6b7c09f 100644
> > --- a/kernel/rcu/rcuperf.c
> > +++ b/kernel/rcu/rcuperf.c
> > @@ -88,6 +88,7 @@ torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
> >  torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
> >  torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
> >  torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
> > +torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
> >  
> >  static char *perf_type = "rcu";
> >  module_param(perf_type, charp, 0444);
> > @@ -635,7 +636,7 @@ kfree_perf_thread(void *arg)
> >  		}
> >  
> >  		for (i = 0; i < kfree_alloc_num; i++) {
> > -			alloc_ptr = kmalloc(sizeof(struct kfree_obj), GFP_KERNEL);
> > +			alloc_ptr = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
> >  			if (!alloc_ptr)
> >  				return -ENOMEM;
> >  
> > @@ -722,6 +723,8 @@ kfree_perf_init(void)
> >  		schedule_timeout_uninterruptible(1);
> >  	}
> >  
> > +	pr_alert("kfree object size=%lu\n", kfree_mult * sizeof(struct kfree_obj));
> > +
> >  	kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]),
> >  			       GFP_KERNEL);
> >  	if (kfree_reader_tasks == NULL) {
> > -- 
> > 2.25.1.481.gfbce0eb801-goog