Commit f77b9672 authored by Reinette Chatre's avatar Reinette Chatre Committed by Shuah Khan
Browse files

selftests/resctrl: Use cache size to determine "fill_buf" buffer size 



By default the MBM and MBA tests use the "fill_buf" benchmark to
read from a buffer with the goal to measure the memory bandwidth
generated by this buffer access.

Care should be taken when sizing the buffer used by the "fill_buf"
benchmark. If the buffer is small enough to fit in the cache then
it cannot be expected that the benchmark will generate much memory
bandwidth. For example, on a system with 320MB L3 cache the existing
hardcoded default of 250MB is insufficient.

Use the measured cache size to determine a buffer size that can be
expected to trigger memory access while keeping the existing default
as minimum, now renamed to MINIMUM_SPAN, that has been appropriate for
testing so far.

Signed-off-by: default avatarReinette Chatre <reinette.chatre@intel.com>
Reviewed-by: default avatarIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: default avatarShuah Khan <skhan@linuxfoundation.org>
parent 3cb3f0b8

tools/testing/selftests/resctrl/fill_buf.c

+13 −0
Original line number Diff line number Diff line
@@ -129,3 +129,16 @@ unsigned char *alloc_buffer(size_t buf_size, bool memflush) 


	return buf;

}



ssize_t get_fill_buf_size(int cpu_no, const char *cache_type)

{

	unsigned long cache_total_size = 0;

	int ret;



	ret = get_cache_size(cpu_no, cache_type, &cache_total_size);

	if (ret)

		return ret;



	return cache_total_size * 2 > MINIMUM_SPAN ?

			cache_total_size * 2 : MINIMUM_SPAN;

}

tools/testing/selftests/resctrl/mba_test.c

+6 −1
Original line number Diff line number Diff line
@@ -182,7 +182,12 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param 
		fill_buf.memflush = uparams->fill_buf->memflush;

		param.fill_buf = &fill_buf;

	} else if (!uparams->benchmark_cmd[0]) {

		fill_buf.buf_size = DEFAULT_SPAN;

		ssize_t buf_size;



		buf_size = get_fill_buf_size(uparams->cpu, "L3");

		if (buf_size < 0)

			return buf_size;

		fill_buf.buf_size = buf_size;

		fill_buf.memflush = true;

		param.fill_buf = &fill_buf;

	}

tools/testing/selftests/resctrl/mbm_test.c

+6 −1
Original line number Diff line number Diff line
@@ -149,7 +149,12 @@ static int mbm_run_test(const struct resctrl_test *test, const struct user_param 
		fill_buf.memflush = uparams->fill_buf->memflush;

		param.fill_buf = &fill_buf;

	} else if (!uparams->benchmark_cmd[0]) {

		fill_buf.buf_size = DEFAULT_SPAN;

		ssize_t buf_size;



		buf_size = get_fill_buf_size(uparams->cpu, "L3");

		if (buf_size < 0)

			return buf_size;

		fill_buf.buf_size = buf_size;

		fill_buf.memflush = true;

		param.fill_buf = &fill_buf;

	}

tools/testing/selftests/resctrl/resctrl.h

+2 −1
Original line number Diff line number Diff line
@@ -41,7 +41,7 @@ 


#define BENCHMARK_ARGS		64



#define DEFAULT_SPAN		(250 * MB)

#define MINIMUM_SPAN		(250 * MB)



/*

 * fill_buf_param:	"fill_buf" benchmark parameters
@@ -169,6 +169,7 @@ int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu, 
unsigned char *alloc_buffer(size_t buf_size, bool memflush);

void mem_flush(unsigned char *buf, size_t buf_size);

void fill_cache_read(unsigned char *buf, size_t buf_size, bool once);

ssize_t get_fill_buf_size(int cpu_no, const char *cache_type);

int initialize_read_mem_bw_imc(void);

int measure_read_mem_bw(const struct user_params *uparams,

			struct resctrl_val_param *param, pid_t bm_pid);

tools/testing/selftests/resctrl/resctrl_tests.c

+1 −1
Original line number Diff line number Diff line
@@ -189,7 +189,7 @@ static struct fill_buf_param *alloc_fill_buf_param(struct user_params *uparams) 
			ksft_exit_skip("Unable to parse benchmark buffer size.\n");

		}

	} else {

		fill_param->buf_size = DEFAULT_SPAN;

		fill_param->buf_size = MINIMUM_SPAN;

	}



	if (uparams->benchmark_cmd[2] && *uparams->benchmark_cmd[2] != '\0') {