Commit 0d11cf93 authored by Jim Harris's avatar Jim Harris Committed by Tomasz Zawadzki
Browse files

bdevperf: use rand_r() twice to get 64-bit values 



rand_r() only returns up to RAND_MAX which is
INT32_MAX.  This means that on sufficiently large
bdevs, especially with smaller block sizes, bdevperf
may not be issuing I/O across the full range of the
bdev.

Found while investigating issue #2908.

Signed-off-by: default avatarJim Harris <james.r.harris@intel.com>
Change-Id: I16db684a57a96f138e709008bded4471428944b6
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/16768


Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarAleksey Marchuk <alexeymar@nvidia.com>
Reviewed-by: default avatarTomasz Zawadzki <tomasz.zawadzki@intel.com>
parent df45f114

examples/bdev/bdevperf/bdevperf.c

+7 −1
Original line number Diff line number Diff line
@@ -1094,11 +1094,17 @@ static void 
bdevperf_submit_single(struct bdevperf_job *job, struct bdevperf_task *task)

{

	uint64_t offset_in_ios;

	uint64_t rand_value;



	if (job->zipf) {

		offset_in_ios = spdk_zipf_generate(job->zipf);

	} else if (job->is_random) {

		offset_in_ios = rand_r(&job->seed) % job->size_in_ios;

		/* RAND_MAX is only INT32_MAX, so use 2 calls to rand_r to

		 * get a large enough value to ensure we are issuing I/O

		 * uniformly across the whole bdev.

		 */

		rand_value = (uint64_t)rand_r(&job->seed) * RAND_MAX + rand_r(&job->seed);

		offset_in_ios = rand_value % job->size_in_ios;

	} else {

		offset_in_ios = job->offset_in_ios++;

		if (job->offset_in_ios == job->size_in_ios) {