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Subject: Re: [PATCH] selftests/vm: 10x speedup for hmm-tests
To:     Andrew Morton <akpm@linux-foundation.org>
CC:     Shuah Khan <shuah@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        <linux-mm@kvack.org>, <linux-kselftest@vger.kernel.org>,
        Ralph Campbell <rcampbell@nvidia.com>
References: <20201003011721.44238-1-jhubbard@nvidia.com>
From:   John Hubbard <jhubbard@nvidia.com>
Message-ID: <6c07b012-4cfc-e89c-43f0-13266d71bf8c@nvidia.com>
Date:   Tue, 6 Oct 2020 13:34:38 -0700
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On 10/2/20 6:17 PM, John Hubbard 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. Thanks to Ralph Campbell
> for suggesting changing NTIMES as a way to get the speedup.
> 
> Suggested-by: Ralph Campbell <rcampbell@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---

Andrew, do you think we can get this one merged into mmotm? I think it's
pretty low risk.


thanks,
-- 
John Hubbard
NVIDIA

> 
> 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)))
>   
>