linux-kernel - Re: [PATCH-next 2/5] lib/test_vmalloc.c: add a new 'nr

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Date:   Mon, 5 Apr 2021 19:39:20 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH-next 2/5] lib/test_vmalloc.c: add a new 'nr_threads'
 parameter

On Sat, 3 Apr 2021 14:31:43 +0200 Uladzislau Rezki <urezki@...il.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.