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From:   Uladzislau Rezki <urezki@gmail.com>
Date:   Tue, 6 Apr 2021 12:05:05 +0200
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Uladzislau Rezki <urezki@gmail.com>, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>,
        Hillf Danton <hdanton@sina.com>,
        Michal Hocko <mhocko@suse.com>,
        Matthew Wilcox <willy@infradead.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH-next 2/5] lib/test_vmalloc.c: add a new 'nr_threads'
 parameter
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 <20210402202237.20334-2-urezki@gmail.com>
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 <20210403123143.GA38147@pc638.lan>
 <20210405193920.46d3792200ad05f4a7c66829@linux-foundation.org>
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On Mon, Apr 05, 2021 at 07:39:20PM -0700, Andrew Morton wrote:
> On Sat, 3 Apr 2021 14:31:43 +0200 Uladzislau Rezki <urezki@gmail.com> wrote:
> 
> > > 
> > > We may need to replaced that kcalloc() with kmvalloc() though...
> > >
> > Yep. If we limit to USHRT_MAX, the maximum amount of memory for
> > internal data would be ~12MB. Something like below:
> > 
> > diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c
> > index d337985e4c5e..a5103e3461bf 100644
> > --- a/lib/test_vmalloc.c
> > +++ b/lib/test_vmalloc.c
> > @@ -24,7 +24,7 @@
> >         MODULE_PARM_DESC(name, msg)                             \
> > 
> >  __param(int, nr_threads, 0,
> > -       "Number of workers to perform tests(min: 1 max: 1024)");
> > +       "Number of workers to perform tests(min: 1 max: 65536)");
> > 
> >  __param(bool, sequential_test_order, false,
> >         "Use sequential stress tests order");
> > @@ -469,13 +469,13 @@ init_test_configurtion(void)
> >  {
> >         /*
> >          * A maximum number of workers is defined as hard-coded
> > -        * value and set to 1024. We add such gap just in case
> > +        * value and set to 65536. We add such gap just in case
> >          * and for potential heavy stressing.
> >          */
> > -       nr_threads = clamp(nr_threads, 1, 1024);
> > +       nr_threads = clamp(nr_threads, 1, 65536);
> > 
> >         /* Allocate the space for test instances. */
> > -       tdriver = kcalloc(nr_threads, sizeof(*tdriver), GFP_KERNEL);
> > +       tdriver = kvcalloc(nr_threads, sizeof(*tdriver), GFP_KERNEL);
> >         if (tdriver == NULL)
> >                 return -1;
> > 
> > @@ -555,7 +555,7 @@ static void do_concurrent_test(void)
> >                         i, t->stop - t->start);
> >         }
> > 
> > -       kfree(tdriver);
> > +       kvfree(tdriver);
> >  }
> > 
> >  static int vmalloc_test_init(void)
> > 
> > Does it sound reasonable for you?
> 
> I think so.  It's a test thing so let's give testers more flexibility,
> remembering that they don't need as much protection from their own
> mistakes.
> 
OK. I will send one more extra patch then.

--
Vlad Rezki