linux-kernel - Re: [PATCH 02/24] selftests/resctrl: Refactor fill

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Date:   Fri, 27 Oct 2023 13:32:31 +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 02/24] selftests/resctrl: Refactor fill_buf functions

On 2023-10-24 at 12:26:12 +0300, Ilpo Järvinen wrote:
>There are unnecessary nested calls in fill_buf.c:
>  - run_fill_buf() calls fill_cache()
>  - alloc_buffer() calls malloc_and_init_memory()
>
>Simplify the code flow and remove those unnecessary call levels by
>moving the called code inside the calling function.
>
>Resolve the difference in run_fill_buf() and fill_cache() parameter
>name into 'buf_size' which is more descriptive than 'span'.
>
>Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
>---
> tools/testing/selftests/resctrl/fill_buf.c | 58 +++++++---------------
> tools/testing/selftests/resctrl/resctrl.h  |  2 +-
> 2 files changed, 20 insertions(+), 40 deletions(-)
>
>diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
>index f9893edda869..9d0b0bf4b85a 100644
>--- a/tools/testing/selftests/resctrl/fill_buf.c
>+++ b/tools/testing/selftests/resctrl/fill_buf.c
>@@ -51,29 +51,6 @@ static void mem_flush(unsigned char *buf, size_t buf_size)
> 	sb();
> }
> 
>-static void *malloc_and_init_memory(size_t buf_size)
>-{
>-	void *p = NULL;
>-	uint64_t *p64;
>-	size_t s64;
>-	int ret;
>-
>-	ret = posix_memalign(&p, PAGE_SIZE, buf_size);
>-	if (ret < 0)
>-		return NULL;
>-
>-	p64 = (uint64_t *)p;
>-	s64 = buf_size / sizeof(uint64_t);
>-
>-	while (s64 > 0) {
>-		*p64 = (uint64_t)rand();
>-		p64 += (CL_SIZE / sizeof(uint64_t));
>-		s64 -= (CL_SIZE / sizeof(uint64_t));
>-	}
>-
>-	return p;
>-}
>-
> static int fill_one_span_read(unsigned char *buf, size_t buf_size)
> {
> 	unsigned char *end_ptr = buf + buf_size;
>@@ -137,20 +114,33 @@ static int fill_cache_write(unsigned char *buf, size_t buf_size, bool once)
> 
> static unsigned char *alloc_buffer(size_t buf_size, int memflush)
> {
>-	unsigned char *buf;
>+	void *p = NULL;

Is this initialization doing anything? "p" seems to be either overwritten or in
case of an error never accessed.

>+	uint64_t *p64;
>+	size_t s64;
>+	int ret;
> 
>-	buf = malloc_and_init_memory(buf_size);
>-	if (!buf)
>+	ret = posix_memalign(&p, PAGE_SIZE, buf_size);
>+	if (ret < 0)
> 		return NULL;
> 
>+	/* Initialize the buffer */
>+	p64 = (uint64_t *)p;
>+	s64 = buf_size / sizeof(uint64_t);
>+
>+	while (s64 > 0) {
>+		*p64 = (uint64_t)rand();
>+		p64 += (CL_SIZE / sizeof(uint64_t));
>+		s64 -= (CL_SIZE / sizeof(uint64_t));
>+	}
>+
> 	/* Flush the memory before using to avoid "cache hot pages" effect */
> 	if (memflush)
>-		mem_flush(buf, buf_size);
>+		mem_flush(p, buf_size);

Wouldn't renaming "p" to "buf" keep this relationship with "buf_size" more
explicit?

Or is naming void pointers "buffers" not appropriate?

> 
>-	return buf;
>+	return p;
> }

-- 
Kind regards
Maciej Wieczór-Retman