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SubjectRe: [PATCH V1 09/13] selftests/resctrl: Modularize fill_buf for new CAT test case
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Hi Sai,

On 3/6/2020 7:40 PM, Sai Praneeth Prakhya wrote:
> Currently fill_buf (in-built benchmark) runs as a separate process and it
> runs indefinitely looping around given buffer either reading it or writing
> to it. But, some future test cases might want to start and stop looping
> around the buffer as they see fit. So, modularize fill_buf to support this
> use case.
>
> Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
> ---
> tools/testing/selftests/resctrl/fill_buf.c | 66 ++++++++++++++++++++----------
> 1 file changed, 44 insertions(+), 22 deletions(-)
>
> diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
> index 9ede7b63f059..204ae8870a32 100644
> --- a/tools/testing/selftests/resctrl/fill_buf.c
> +++ b/tools/testing/selftests/resctrl/fill_buf.c
> @@ -23,7 +23,7 @@
> #define PAGE_SIZE (4 * 1024)
> #define MB (1024 * 1024)
>
> -static unsigned char *startptr;
> +static unsigned char *startptr, *endptr;
>
> static void sb(void)
> {
> @@ -82,13 +82,13 @@ static void *malloc_and_init_memory(size_t s)
> return p;
> }
>
> -static int fill_one_span_read(unsigned char *start_ptr, unsigned char *end_ptr)
> +static int fill_one_span_read(void)
> {
> unsigned char sum, *p;
>
> sum = 0;
> - p = start_ptr;
> - while (p < end_ptr) {
> + p = startptr;
> + while (p < endptr) {
> sum += *p;
> p += (CL_SIZE / 2);
> }
> @@ -96,26 +96,24 @@ static int fill_one_span_read(unsigned char *start_ptr, unsigned char *end_ptr)
> return sum;
> }
>
> -static
> -void fill_one_span_write(unsigned char *start_ptr, unsigned char *end_ptr)
> +static void fill_one_span_write(void)
> {
> unsigned char *p;
>
> - p = start_ptr;
> - while (p < end_ptr) {
> + p = startptr;
> + while (p < endptr) {
> *p = '1';
> p += (CL_SIZE / 2);
> }
> }
>
> -static int fill_cache_read(unsigned char *start_ptr, unsigned char *end_ptr,
> - char *resctrl_val)
> +static int fill_cache_read(char *resctrl_val)
> {
> int ret = 0;
> FILE *fp;
>
> while (1) {
> - ret = fill_one_span_read(start_ptr, end_ptr);
> + ret = fill_one_span_read();
> if (!strcmp(resctrl_val, "cat"))
> break;
> }
> @@ -130,11 +128,10 @@ static int fill_cache_read(unsigned char *start_ptr, unsigned char *end_ptr,
> return 0;
> }
>
> -static int fill_cache_write(unsigned char *start_ptr, unsigned char *end_ptr,
> - char *resctrl_val)
> +static int fill_cache_write(char *resctrl_val)
> {
> while (1) {
> - fill_one_span_write(start_ptr, end_ptr);
> + fill_one_span_write();
> if (!strcmp(resctrl_val, "cat"))
> break;
> }
> @@ -142,24 +139,25 @@ static int fill_cache_write(unsigned char *start_ptr, unsigned char *end_ptr,
> return 0;
> }
>
> -static int
> -fill_cache(unsigned long long buf_size, int malloc_and_init, int memflush,
> - int op, char *resctrl_val)
> +static
> +int init_buffer(unsigned long long buf_size, int malloc_and_init, int memflush)
> {
> unsigned char *start_ptr, *end_ptr;
> unsigned long long i;
> - int ret;
>
> if (malloc_and_init)
> start_ptr = malloc_and_init_memory(buf_size);
> else
> start_ptr = malloc(buf_size);
>
> - if (!start_ptr)
> + if (!start_ptr) {
> + printf("Failed to allocate memory to buffer\n");
> return -1;
> + }
>
> - startptr = start_ptr;
> end_ptr = start_ptr + buf_size;
> + endptr = end_ptr;
> + startptr = start_ptr;
>
> /*
> * It's better to touch the memory once to avoid any compiler
> @@ -176,16 +174,40 @@ fill_cache(unsigned long long buf_size, int malloc_and_init, int memflush,
> if (memflush)
> mem_flush(start_ptr, buf_size);
>
> + return 0;
> +}
> +
> +static int use_buffer_forever(int op, char *resctrl_val)
> +{
> + int ret;
> +
> if (op == 0)
> - ret = fill_cache_read(start_ptr, end_ptr, resctrl_val);
> + ret = fill_cache_read(resctrl_val);
> else
> - ret = fill_cache_write(start_ptr, end_ptr, resctrl_val);
> + ret = fill_cache_write(resctrl_val);
>
> if (ret) {
> printf("\n Errror in fill cache read/write...\n");
> return -1;
> }
>
> + return 0;
> +}
> +
> +static int
> +fill_cache(unsigned long long buf_size, int malloc_and_init, int memflush,
> + int op, char *resctrl_val)
> +{
> + int ret;
> +
> + ret = init_buffer(buf_size, malloc_and_init, memflush);
> + if (ret)
> + return ret;
> +
> + ret = use_buffer_forever(op, resctrl_val);
> + if (ret)
> + return ret;

Should buffer be freed on this error path?

I think the asymmetrical nature of the memory allocation and release
creates traps like this.

It may be less error prone to have the pointer returned by init_buffer
and the acted on and released within fill_cache(), passed to
"use_buffer_forever()" as a parameter. The buffer size is known here,
there is no need to keep an "end pointer" around.

> +
> free(startptr);
>
> return 0;
>

Reinette

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