Re: [PATCH v2] drm/sched: Add test suite for concurrent job submissions

[Marco Pagani <marco.pagani@linux.dev>]

On 09/04/2026 17:35, Tvrtko Ursulin wrote:
> 
> On 08/04/2026 16:49, Marco Pagani wrote:
>> Add a new test suite to simulate concurrent job submissions to the DRM
>> scheduler, as this functionality is not covered by current test suites.
>>
>> The new test suite includes two initial test cases: (i) a test case for
>> parallel job submission and (ii) a test case for interleaved job
>> submission and completion. In the first test case, worker threads
>> concurrently submit jobs to the scheduler, and then the timeline is
>> manually advanced to complete them in bulk. In the second test case,
>> worker threads concurrently submit sequences of jobs of different
>> durations to the mock scheduler using a sliding window to better model
>> real-world workloads. The timeline is advanced automatically by the
>> finishing jobs, interleaving submission with completion.
>>
>> Signed-off-by: Marco Pagani <marco.pagani@linux.dev>
>> ---
>> Changes in v2:
>> - Improved test description
>> - Use multiple job durations instead of harmonic periods/durations
>> - Improved submission for interleaved test with a sliding window
>> - Removed unnecessary asserts per Tvrtko's feedback, but kept wait_scheduled
>> - Changed parameter names from period to duration for clarity
>> - Used temp variables to reduce line breaks
>> ---
>>   drivers/gpu/drm/scheduler/tests/tests_basic.c | 356 ++++++++++++++++++
>>   1 file changed, 356 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/scheduler/tests/tests_basic.c b/drivers/gpu/drm/scheduler/tests/tests_basic.c
>> index a5a5a35a87b0..1791b157cfc8 100644
>> --- a/drivers/gpu/drm/scheduler/tests/tests_basic.c
>> +++ b/drivers/gpu/drm/scheduler/tests/tests_basic.c
>> @@ -1,7 +1,11 @@
>>   // SPDX-License-Identifier: GPL-2.0
>>   /* Copyright (c) 2025 Valve Corporation */
>>   
>> +#include <linux/completion.h>
>>   #include <linux/delay.h>
>> +#include <linux/minmax.h>
>> +#include <linux/time.h>
>> +#include <linux/workqueue.h>
>>   
>>   #include "sched_tests.h"
>>   
>> @@ -235,6 +239,357 @@ static void drm_sched_basic_cancel(struct kunit *test)
>>   	KUNIT_ASSERT_EQ(test, job->hw_fence.error, -ECANCELED);
>>   }
>>   
>> +struct sched_concurrent_context {
>> +	struct drm_mock_scheduler *sched;
>> +	struct workqueue_struct *sub_wq;
>> +	struct kunit *test;
>> +	struct completion wait_go;
>> +};
>> +
>> +KUNIT_DEFINE_ACTION_WRAPPER(drm_mock_sched_fini_wrap, drm_mock_sched_fini,
>> +			    struct drm_mock_scheduler *);
>> +
>> +KUNIT_DEFINE_ACTION_WRAPPER(drm_mock_sched_entity_free_wrap, drm_mock_sched_entity_free,
>> +			    struct drm_mock_sched_entity *);
>> +
>> +static void complete_destroy_workqueue(void *context)
>> +{
>> +	struct sched_concurrent_context *ctx = context;
>> +
>> +	complete_all(&ctx->wait_go);
>> +
>> +	destroy_workqueue(ctx->sub_wq);
>> +}
>> +
>> +static int drm_sched_concurrent_init(struct kunit *test)
>> +{
>> +	struct sched_concurrent_context *ctx;
>> +	int ret;
>> +
>> +	ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
>> +	KUNIT_ASSERT_NOT_NULL(test, ctx);
>> +
>> +	init_completion(&ctx->wait_go);
>> +
>> +	ctx->sched = drm_mock_sched_new(test, MAX_SCHEDULE_TIMEOUT);
>> +
>> +	ret = kunit_add_action_or_reset(test, drm_mock_sched_fini_wrap, ctx->sched);
>> +	KUNIT_ASSERT_EQ(test, ret, 0);
>> +
>> +	/* Use an unbounded workqueue to maximize job submission concurrency */
>> +	ctx->sub_wq = alloc_workqueue("drm-sched-submitters-wq", WQ_UNBOUND,
>> +				      WQ_UNBOUND_MAX_ACTIVE);
>> +	KUNIT_ASSERT_NOT_NULL(test, ctx->sub_wq);
>> +
>> +	ret = kunit_add_action_or_reset(test, complete_destroy_workqueue, ctx);
>> +	KUNIT_ASSERT_EQ(test, ret, 0);
>> +
>> +	ctx->test = test;
>> +	test->priv = ctx;
>> +
>> +	return 0;
>> +}
>> +
>> +struct drm_sched_parallel_params {
>> +	const char *description;
>> +	unsigned int num_jobs;
>> +	unsigned int num_workers;
>> +};
>> +
>> +static const struct drm_sched_parallel_params drm_sched_parallel_cases[] = {
>> +	{
>> +		.description = "Parallel submission of multiple jobs per worker",
>> +		.num_jobs = 8,
>> +		.num_workers = 16,
>> +	},
>> +};
>> +
>> +static void
>> +drm_sched_parallel_desc(const struct drm_sched_parallel_params *params, char *desc)
>> +{
>> +	strscpy(desc, params->description, KUNIT_PARAM_DESC_SIZE);
>> +}
>> +
>> +KUNIT_ARRAY_PARAM(drm_sched_parallel, drm_sched_parallel_cases, drm_sched_parallel_desc);
> 
> As long as you don't plan to add more test cases any time soon the 
> boiler plate could be reduced by unot using KUNIT_ARRAY_PARAM but it is 
> up to you. (Same for the other test below.)

Right.

>> +
>> +struct parallel_worker {
>> +	struct work_struct work;
>> +	struct sched_concurrent_context *ctx;
>> +	struct drm_mock_sched_entity *entity;
>> +	struct drm_mock_sched_job **jobs;
>> +	unsigned int id;
>> +};
>> +
>> +static void drm_sched_parallel_worker(struct work_struct *work)
>> +{
>> +	const struct drm_sched_parallel_params *params;
>> +	struct sched_concurrent_context *test_ctx;
>> +	struct parallel_worker *worker;
>> +	unsigned int i;
>> +
>> +	worker = container_of(work, struct parallel_worker, work);
>> +	test_ctx = worker->ctx;
>> +	params = test_ctx->test->param_value;
>> +
>> +	wait_for_completion(&test_ctx->wait_go);
>> +
>> +	kunit_info(test_ctx->test, "Parallel worker %u submitting %u jobs started\n",
>> +		   worker->id, params->num_jobs);
>> +
>> +	for (i = 0; i < params->num_jobs; i++)
>> +		drm_mock_sched_job_submit(worker->jobs[i]);
>> +}
>> +
>> +/*
>> + * Spawns workers that submit a sequence of jobs to the mock scheduler.
>> + * Once all jobs are submitted, the timeline is manually advanced.
>> + */
>> +static void drm_sched_parallel_submit_test(struct kunit *test)
>> +{
>> +	struct sched_concurrent_context *ctx = test->priv;
>> +	const struct drm_sched_parallel_params *params = test->param_value;
>> +	struct parallel_worker *workers, *worker;
>> +	struct drm_mock_sched_job *job;
>> +	unsigned int i, j, completed_jobs, total_jobs;
>> +	bool done;
>> +	int ret;
>> +
>> +	KUNIT_ASSERT_GT(test, params->num_workers, 0);
>> +	KUNIT_ASSERT_GT(test, params->num_jobs, 0);
>> +
>> +	workers = kunit_kcalloc(test, params->num_workers, sizeof(*workers),
>> +				GFP_KERNEL);
>> +	KUNIT_ASSERT_NOT_NULL(test, workers);
>> +
>> +	/*
>> +	 * Init workers only after all jobs and entities have been successfully
>> +	 * allocated. In this way, the cleanup logic for when an assertion fail
>> +	 * can be simplified.
>> +	 */
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		worker->id = i;
>> +		worker->ctx = ctx;
>> +		worker->entity = drm_mock_sched_entity_new(test,
>> +							   DRM_SCHED_PRIORITY_NORMAL,
>> +							   ctx->sched);
>> +
>> +		ret = kunit_add_action_or_reset(test, drm_mock_sched_entity_free_wrap,
>> +						worker->entity);
>> +		KUNIT_ASSERT_EQ(test, ret, 0);
>> +
>> +		worker->jobs = kunit_kcalloc(test, params->num_jobs,
>> +					     sizeof(*worker->jobs), GFP_KERNEL);
>> +		KUNIT_ASSERT_NOT_NULL(test, worker->jobs);
>> +
>> +		for (j = 0; j < params->num_jobs; j++) {
>> +			job = drm_mock_sched_job_new(test, worker->entity);
>> +			worker->jobs[j] = job;
>> +		}
>> +	}
>> +
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		INIT_WORK(&worker->work, drm_sched_parallel_worker);
>> +		queue_work(ctx->sub_wq, &worker->work);
>> +	}
>> +
>> +	complete_all(&ctx->wait_go);
>> +	flush_workqueue(ctx->sub_wq);
>> +
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		for (j = 0; j < params->num_jobs; j++) {
>> +			job = worker->jobs[j];
>> +			done = drm_mock_sched_job_wait_scheduled(job, HZ);
>> +			KUNIT_EXPECT_TRUE(test, done);
>> +		}
>> +	}
>> +
>> +	total_jobs = params->num_workers * params->num_jobs;
>> +	completed_jobs = drm_mock_sched_advance(ctx->sched, total_jobs);
>> +	KUNIT_EXPECT_EQ(test, completed_jobs, total_jobs);
>> +
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		for (j = 0; j < params->num_jobs; j++) {
>> +			job = worker->jobs[j];
>> +			done = drm_mock_sched_job_wait_finished(job, HZ);
>> +			KUNIT_EXPECT_TRUE(test, done);
>> +		}
>> +	}
>> +}
>> +
>> +struct drm_sched_interleaved_params {
>> +	const char *description;
>> +	unsigned int test_duration_ms;
>> +	unsigned int job_base_duration_us;
>> +	unsigned int num_workers;
>> +	unsigned int num_in_flight_jobs;
>> +};
>> +
>> +static const struct drm_sched_interleaved_params drm_sched_interleaved_cases[] = {
>> +	{
>> +		.description = "Interleaved submission of multiple jobs per worker",
>> +		.test_duration_ms = 1000,
>> +		.job_base_duration_us = 100,
>> +		.num_workers = 16,
>> +		.num_in_flight_jobs = 8,
>> +	},
>> +};
>> +
>> +static void
>> +drm_sched_interleaved_desc(const struct drm_sched_interleaved_params *params, char *desc)
>> +{
>> +	strscpy(desc, params->description, KUNIT_PARAM_DESC_SIZE);
>> +}
>> +
>> +KUNIT_ARRAY_PARAM(drm_sched_interleaved, drm_sched_interleaved_cases,
>> +		  drm_sched_interleaved_desc);
>> +
>> +struct interleaved_worker {
>> +	struct work_struct work;
>> +	struct sched_concurrent_context *ctx;
>> +	struct drm_mock_sched_entity *entity;
>> +	struct drm_mock_sched_job **jobs;
>> +	unsigned int id;
>> +	unsigned int job_count;
>> +	unsigned int job_duration_us;
>> +};
>> +
>> +static void drm_sched_interleaved_worker(struct work_struct *work)
>> +{
>> +	struct sched_concurrent_context *test_ctx;
>> +	const struct drm_sched_interleaved_params *params;
>> +	struct interleaved_worker *worker;
>> +	unsigned int i, j, max_in_flight_job;
>> +	unsigned long timeout;
>> +	bool done;
>> +
>> +	worker = container_of(work, struct interleaved_worker, work);
>> +	test_ctx = worker->ctx;
>> +	params = test_ctx->test->param_value;
>> +
>> +	wait_for_completion(&test_ctx->wait_go);
>> +
>> +	kunit_info(test_ctx->test, "Worker %u submitting %u jobs of %u us started\n",
>> +		   worker->id, worker->job_count, worker->job_duration_us);
>> +
>> +	timeout = msecs_to_jiffies(params->test_duration_ms * 2);
>> +
>> +	/* Fill the submission window */
>> +	max_in_flight_job = min(worker->job_count, params->num_in_flight_jobs);
>> +	for (i = 0; i < max_in_flight_job; i++)
>> +		drm_mock_sched_job_submit(worker->jobs[i]);
>> +
>> +	/* Keep the window full by submitting a new job at once until done */
>> +	for (i = 0; i < worker->job_count; i++) {
>> +		done = drm_mock_sched_job_wait_finished(worker->jobs[i], timeout);
>> +		if (!done)
>> +			kunit_info(test_ctx->test, "Job %u of worker %u timed out\n",
>> +				   i, worker->id);
>> +
>> +		j = i + max_in_flight_job;
>> +		if (j < worker->job_count)
>> +			drm_mock_sched_job_submit(worker->jobs[j]);
>> +	}
> 
> The loop maybe isn't the most straight-forward but eventually looked to 
> me like it will do what it wants.

I will address this in my reply to your next message.

> num_in_flight_jobs as a test parameter is perhaps arbitrary? I am not 
> sure what it aims to achieve versus if workers would just be submitting 
> one by one, or perhaps two by two, in both cases loops would be simpler.

I think it's better to have it as a parameter rather than hardcoded in
the test.
 
> Or even if num_in_flight_jobs would perhaps be automatically derived 
> from the worker->id? If the goal is to simulate queue depth it sounds 
> good to vary it.

That's a nice idea, but I think having a fixed number of in_flight_jobs
expressed as a parameter is a good balance between test expressiveness
and simplicity.

> But these are minor points and up to you. The test now looks passably 
> tidy as it is.

Thanks for the tidy encouragement.

> Ah wait, please also check if this one needs to be marked as "slow" 
> kunit test. AFAIR all that are expected to take more than 1s need that.

I've run it with UML and QEMU (arch=x86_64) and with the current parameters
kunit does not recommend to mark it as slow. But maybe you are right, it's
safer to mark it as slow anyway.

Thanks,
Marco

> 
>> +}
>> +
>> +/*
>> + * Spawns workers that submit a sequence of jobs to the mock scheduler. Job
>> + * durations are chosen as multiples of a base duration value specified as
>> + * a test parameter. Since the scheduler serializes jobs from all workers,
>> + * the total test duration budget is divided into equal shares among workers.
>> + * These shares are then used to compute the number of jobs that each worker
>> + * can submit
>> + */
>> +static void drm_sched_interleaved_submit_test(struct kunit *test)
>> +{
>> +	const struct drm_sched_interleaved_params *params = test->param_value;
>> +	struct sched_concurrent_context *ctx = test->priv;
>> +	struct interleaved_worker *workers, *worker;
>> +	struct drm_mock_sched_job *job;
>> +	unsigned int worker_share_us;
>> +	unsigned int i, j;
>> +	bool done;
>> +	int ret;
>> +
>> +	KUNIT_ASSERT_GT(test, params->num_workers, 0);
>> +	KUNIT_ASSERT_GT(test, params->job_base_duration_us, 0);
>> +
>> +	workers = kunit_kcalloc(test, params->num_workers, sizeof(*workers),
>> +				GFP_KERNEL);
>> +	KUNIT_ASSERT_NOT_NULL(test, workers);
>> +
>> +	/* Divide the available test time into equal shares among the workers */
>> +	worker_share_us = (params->test_duration_ms * USEC_PER_MSEC) /
>> +			  params->num_workers;
>> +
>> +	/*
>> +	 * Init workers only after all jobs and entities have been successfully
>> +	 * allocated. In this way, the cleanup logic for when an assertion fails
>> +	 * can be simplified.
>> +	 */
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		worker->id = i;
>> +		worker->ctx = ctx;
>> +
>> +		worker->job_duration_us = params->job_base_duration_us * (i + 1);
>> +		worker->job_count = worker_share_us / worker->job_duration_us;
>> +		worker->job_count = max(1U, worker->job_count);
>> +
>> +		worker->entity = drm_mock_sched_entity_new(test,
>> +							   DRM_SCHED_PRIORITY_NORMAL,
>> +							   ctx->sched);
>> +
>> +		ret = kunit_add_action_or_reset(test, drm_mock_sched_entity_free_wrap,
>> +						worker->entity);
>> +		KUNIT_ASSERT_EQ(test, ret, 0);
>> +
>> +		worker->jobs = kunit_kcalloc(test, worker->job_count,
>> +					     sizeof(*worker->jobs), GFP_KERNEL);
>> +		KUNIT_ASSERT_NOT_NULL(test, worker->jobs);
>> +
>> +		for (j = 0; j < worker->job_count; j++) {
>> +			job = drm_mock_sched_job_new(test, worker->entity);
>> +			drm_mock_sched_job_set_duration_us(job, worker->job_duration_us);
>> +
>> +			worker->jobs[j] = job;
>> +		}
>> +	}
>> +
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		INIT_WORK(&worker->work, drm_sched_interleaved_worker);
>> +		queue_work(ctx->sub_wq, &worker->work);
>> +	}
>> +
>> +	complete_all(&ctx->wait_go);
>> +	flush_workqueue(ctx->sub_wq);
>> +
>> +	for (i = 0; i < params->num_workers; i++) {
>> +		worker = &workers[i];
>> +		for (j = 0; j < worker->job_count; j++) {
>> +			job = worker->jobs[j];
>> +			done = drm_mock_sched_job_is_finished(job);
>> +			KUNIT_EXPECT_TRUE(test, done);
>> +		}
>> +	}
>> +}
>> +
>> +static struct kunit_case drm_sched_concurrent_tests[] = {
>> +	KUNIT_CASE_PARAM(drm_sched_parallel_submit_test, drm_sched_parallel_gen_params),
>> +	KUNIT_CASE_PARAM(drm_sched_interleaved_submit_test, drm_sched_interleaved_gen_params),
>> +	{}
>> +};
>> +
>> +static struct kunit_suite drm_sched_concurrent = {
>> +	.name = "drm_sched_concurrent_tests",
>> +	.init = drm_sched_concurrent_init,
>> +	.test_cases = drm_sched_concurrent_tests,
>> +};
>> +
>>   static struct kunit_case drm_sched_cancel_tests[] = {
>>   	KUNIT_CASE(drm_sched_basic_cancel),
>>   	{}
>> @@ -556,6 +911,7 @@ static struct kunit_suite drm_sched_credits = {
>>   };
>>   
>>   kunit_test_suites(&drm_sched_basic,
>> +		  &drm_sched_concurrent,
>>   		  &drm_sched_timeout,
>>   		  &drm_sched_cancel,
>>   		  &drm_sched_priority,
>