linux-kernel - Re: [PATCH v2 02/26] selftests/resctrl: Split fill

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Date:   Tue, 28 Nov 2023 14:10:20 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        "Shaopeng Tan" <tan.shaopeng@...fujitsu.com>,
        Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 02/26] selftests/resctrl: Split fill_buf to allow tests
 finer-grained control

Hi Ilpo,

On 11/20/2023 3:13 AM, Ilpo Järvinen wrote:
> MBM, MBA and CMT test cases call run_fill_buf() that in turn calls
> fill_cache() to alloc and loop indefinitely around the buffer. This
> binds buffer allocation and running the benchmark into a single bundle
> so that a selftest cannot allocate a buffer once and reuse it. CAT test
> doesn't want to loop around the buffer continuously and after rewrite
> it needs the ability to allocate the buffer separately.
> 
> Split buffer allocation out of fill_cache() into alloc_buffer(). This
> change is part of preparation for the new CAT test that allocates a
> buffer and does multiple passes over the same buffer (but not in an
> infinite loop).
> 
> Co-developed-by: Fenghua Yu <fenghua.yu@...el.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---

Could you please list the changes to a patch in this area instead of
lumping all in the cover letter? Without this it is not clear what,
if anything, changed in the new version.

>  tools/testing/selftests/resctrl/fill_buf.c | 26 +++++++++++++---------
>  1 file changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
> index 0d425f26583a..6f32f44128e1 100644
> --- a/tools/testing/selftests/resctrl/fill_buf.c
> +++ b/tools/testing/selftests/resctrl/fill_buf.c
> @@ -135,33 +135,37 @@ static int fill_cache_write(unsigned char *buf, size_t buf_size, bool once)
>  	return 0;
>  }
>  
> -static int fill_cache(size_t buf_size, int memflush, int op, bool once)
> +static unsigned char *alloc_buffer(size_t buf_size, int memflush)
>  {
>  	unsigned char *buf;
> -	int ret;
>  
>  	buf = malloc_and_init_memory(buf_size);
>  	if (!buf)
> -		return -1;
> +		return NULL;
>  
>  	/* Flush the memory before using to avoid "cache hot pages" effect */
>  	if (memflush)
>  		mem_flush(buf, buf_size);
>  
> +	return buf;
> +}
> +
> +static int fill_cache(size_t buf_size, int memflush, int op, bool once)
> +{
> +	unsigned char *buf;
> +	int ret;
> +
> +	buf = alloc_buffer(buf_size, memflush);
> +	if (!buf)
> +		return -1;
> +
>  	if (op == 0)
>  		ret = fill_cache_read(buf, buf_size, once);
>  	else
>  		ret = fill_cache_write(buf, buf_size, once);
> -
>  	free(buf);
>  
> -	if (ret) {
> -		printf("\n Error in fill cache read/write...\n");
> -		return -1;
> -	}
> -

The changelog does not motivate the removal of this error message.
It seems ok at this point since the only failing functions already
print their own error message. Without a motivation of this change
it is not clear if it is actually intended.

In any case, this looks good.

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette