linux-kernel - Re: [PATCH] lib/test_vmalloc.c: Minor fixes to test

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Message-ID: <aW4XNSD6jzHUZlWn@milan>
Date: Mon, 19 Jan 2026 12:36:21 +0100
From: Uladzislau Rezki <urezki@...il.com>
To: Audra Mitchell <audra@...hat.com>
Cc: Audra Mitchell <audra@...hat.com>, shuah@...nel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, mhocko@...e.com, surenb@...gle.com,
	rppt@...nel.org, vbabka@...e.cz, Liam.Howlett@...cle.com,
	lorenzo.stoakes@...cle.com, david@...nel.org, urezki@...il.com,
	raquini@...hat.com, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] lib/test_vmalloc.c: Minor fixes to test_vmalloc.c

On Sun, Jan 18, 2026 at 05:30:36PM -0800, Andrew Morton wrote:
> On Mon,  1 Dec 2025 13:18:48 -0500 Audra Mitchell <audra@...hat.com> wrote:
> 
> > If PAGE_SIZE is larger than 4k and if you have a system with a
> > large number of CPUs, this test can require a very large amount
> > of memory leading to oom-killer firing. Given the type of allocation,
> > the kernel won't have anything to kill, causing the system to
> > stall. Add a parameter to the test_vmalloc driver to represent the
> > number of times a percpu object will be allocated. Calculate this
> > in test_vmalloc.sh to be 90% of available memory or the current
> > default of 35000, whichever is smaller.
> > 
> > ...
> >
> > --- a/lib/test_vmalloc.c
> > +++ b/lib/test_vmalloc.c
> > @@ -57,6 +57,9 @@ __param(int, run_test_mask, 7,
> >  		/* Add a new test case description here. */
> >  );
> >  
> > +__param(int, nr_pcpu_objects, 35000,
> > +	"Number of pcpu objects to allocate for pcpu_alloc_test");
> > +
> >  /*
> >   * This is for synchronization of setup phase.
> >   */
> > @@ -292,24 +295,24 @@ pcpu_alloc_test(void)
> >  	size_t size, align;
> >  	int i;
> >  
> > -	pcpu = vmalloc(sizeof(void __percpu *) * 35000);
> > +	pcpu = vmalloc(sizeof(void __percpu *) * nr_pcpu_objects);
> 
> Could have used vmalloc_array() here.  Otherwise lgtm, thanks.
> 
We can also reduce the default number from 35 000 to smaller one
since this patch makes it possible to control it via parameter.

--
Uladzislau Rezki