linux-kernel - Re: [PATCH 01/24] selftests/resctrl: Split fill

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Date:   Fri, 27 Oct 2023 13:24:37 +0200
From:   Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC:     <linux-kselftest@...r.kernel.org>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        Shaopeng Tan <tan.shaopeng@...fujitsu.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/24] selftests/resctrl: Split fill_buf to allow tests
 finer-grained control

On 2023-10-24 at 12:26:11 +0300, Ilpo Järvinen wrote:
>MBM, MBA and CMT test cases use run_fill_buf() to loop indefinitely
>around the buffer. CAT test case is different and doesn't want to loop
>around the buffer continuously.
>
>Split fill_cache() so that both the use cases are easier to control by
>creating separate functions for buffer allocation and looping around
>the buffer. Make those functions available for tests. The new interface
>is based on returning/passing pointers instead of the startptr global
>pointer variable that can now be removed. The deallocation can use
>free() directly.
>
>This change is part of preparation for new CAT test which 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>
>---
> 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..f9893edda869 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 == NULL)

Maybe just do:
	if (!buf)?

Checkpatch also seems to suggest this approach:

CHECK: Comparison to NULL could be written "!buf"
#65: FILE: tools/testing/selftests/resctrl/fill_buf.c:159:
+       if (buf == NULL)

>+		return -1;
>+

-- 
Kind regards
Maciej Wieczór-Retman