linux-kernel - Re: [PATCH] selftests/vm: 10x speedup for hmm-tests

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Date:   Sat,  3 Oct 2020 07:23:09 +0200
From:   SeongJae Park <sj38.park@...il.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org,
        Ralph Campbell <rcampbell@...dia.com>
Subject: Re: [PATCH] selftests/vm: 10x speedup for hmm-tests

On Fri, 2 Oct 2020 18:17:21 -0700 John Hubbard <jhubbard@...dia.com> wrote:

> This patch reduces the running time for hmm-tests from about 10+
> seconds, to just under 1.0 second, for an approximately 10x speedup.
> That brings it in line with most of the other tests in selftests/vm,
> which mostly run in < 1 sec.
> 
> This is done with a one-line change that simply reduces the number of
> iterations of several tests, from 256, to 10.

Could this result in reduced test capacity?  If so, how about making the number
easily tweakable?


Thanks,
SeongJae Park

> Thanks to Ralph Campbell for suggesting changing NTIMES as a way to get the
> speedup.
> 
> Suggested-by: Ralph Campbell <rcampbell@...dia.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
> 
> This is based on mmotm.
> 
>  tools/testing/selftests/vm/hmm-tests.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
> index 6b79723d7dc6..5d1ac691b9f4 100644
> --- a/tools/testing/selftests/vm/hmm-tests.c
> +++ b/tools/testing/selftests/vm/hmm-tests.c
> @@ -49,7 +49,7 @@ struct hmm_buffer {
>  #define TWOMEG		(1 << 21)
>  #define HMM_BUFFER_SIZE (1024 << 12)
>  #define HMM_PATH_MAX    64
> -#define NTIMES		256
> +#define NTIMES		10
>  
>  #define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1)))
>  
> -- 
> 2.28.0