Re: [PATCH i-g-t] i915/gem_exec_whisper: Limit workload

[Nirmoy Das <nirmoy.das@linux.intel.com>]

On 3/21/2024 7:30 PM, Jonathan Cavitt wrote:
> From: Chris Wilson <chris.p.wilson@linux.intel.com>
>
> For large machines with lots of cpus and many engines, using a workload
> that tries to use every engine from every cpu causes massive
> oversaturation. The goal of the test workload is to cause saturation on
> both engines and cpus so that we apply some pressure on the scheduler to
> maintain order, but to do so we only need to ensure each scheduling
> queue is saturated and there is sufficient pressure for the CPU
> scheduler to push work across cores. We can impose a limit on the number
> of threads such that we ensure that every engine and every core should
> be occupied. Furthermore we can scale the amount of work submitted by
> each thread to keep the total amount of work under a reasonable time
> bound.
>
> Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>

Need your sign off here. Otherwise

Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>

> CC: Bruce Chang <yu.bruce.chang@intel.com>
> ---
>   tests/intel/gem_exec_whisper.c | 24 +++++++++++++++---------
>   1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/tests/intel/gem_exec_whisper.c b/tests/intel/gem_exec_whisper.c
> index effb473350..429dfc00d5 100644
> --- a/tests/intel/gem_exec_whisper.c
> +++ b/tests/intel/gem_exec_whisper.c
> @@ -294,6 +294,7 @@ static void whisper(int fd, const intel_ctx_t *ctx,
>   {
>   	const uint32_t bbe = MI_BATCH_BUFFER_END;
>   	const unsigned int gen = intel_gen(intel_get_drm_devid(fd));
> +	const unsigned int ncpus = sysconf(_SC_NPROCESSORS_ONLN);
>   	struct drm_i915_gem_exec_object2 batches[QLEN];
>   	struct drm_i915_gem_relocation_entry inter[QLEN];
>   	struct drm_i915_gem_relocation_entry reloc;
> @@ -306,18 +307,19 @@ static void whisper(int fd, const intel_ctx_t *ctx,
>   	int fds[64];
>   	intel_ctx_cfg_t local_cfg;
>   	const intel_ctx_t *contexts[64];
> -	unsigned nengine;
>   	uint32_t batch[16];
>   	unsigned int relocations = 0;
>   	unsigned int reloc_migrations = 0;
>   	unsigned int reloc_interruptions = 0;
>   	unsigned int eb_migrations = 0;
>   	struct power_sample sample[2];
> +	unsigned int nengine;
> +	unsigned int nchild;
> +	unsigned int qlen;
>   	struct igt_power gpu;
>   	uint64_t old_offset;
>   	int i, n, loc;
>   	int debugfs;
> -	int nchild;
>   	bool has_relocs = gem_has_relocations(fd);
>   
>   	if (flags & PRIORITY) {
> @@ -356,9 +358,13 @@ static void whisper(int fd, const intel_ctx_t *ctx,
>   
>   	nchild = 1;
>   	if (flags & FORKED)
> -		nchild *= sysconf(_SC_NPROCESSORS_ONLN);
> +		nchild *= ncpus;
>   	if (flags & ALL)
>   		nchild *= nengine;
> +	nchild = min(nchild, 2 * max(ncpus, nengine));
> +	qlen = max(2u, QLEN * nengine / (nchild + nengine - 1));
> +	igt_info("Using nchild:%d (out of ncpus:%d and nengine:%d), with a qlen:%d\n",
> +		 nchild, ncpus, nengine, qlen);
>   
>   	intel_detect_and_clear_missed_interrupts(fd);
>   	igt_power_get_energy(&gpu, &sample[0]);
> @@ -448,19 +454,19 @@ static void whisper(int fd, const intel_ctx_t *ctx,
>   		}
>   
>   		memset(batches, 0, sizeof(batches));
> -		for (n = 0; n < QLEN; n++) {
> +		for (n = 0; n < qlen; n++) {
>   			batches[n].handle = gem_create(fd, 4096);
>   			gem_write(fd, batches[n].handle, 0, &bbe, sizeof(bbe));
>   		}
>   		execbuf.buffers_ptr = to_user_pointer(batches);
> -		execbuf.buffer_count = QLEN;
> +		execbuf.buffer_count = qlen;
>   		gem_execbuf(fd, &execbuf);
>   
>   		execbuf.buffers_ptr = to_user_pointer(tmp);
>   		execbuf.buffer_count = 2;
>   
>   		old_offset = store.offset;
> -		for (n = 0; n < QLEN; n++) {
> +		for (n = 0; n < qlen; n++) {
>   			if (gen >= 8) {
>   				batch[1] = old_offset + loc;
>   				batch[2] = (old_offset + loc) >> 32;
> @@ -525,8 +531,8 @@ static void whisper(int fd, const intel_ctx_t *ctx,
>   					gem_sync(fd, tmp[0].handle);
>   				scratch = tmp[0];
>   
> -				gem_write(fd, batches[QLEN-1].handle, loc, &pass, sizeof(pass));
> -				for (n = QLEN; --n >= 1; ) {
> +				gem_write(fd, batches[qlen-1].handle, loc, &pass, sizeof(pass));
> +				for (n = qlen; --n >= 1; ) {
>   					uint32_t handle[2] = {};
>   					int this_fd = fd;
>   
> @@ -648,7 +654,7 @@ static void whisper(int fd, const intel_ctx_t *ctx,
>   				gem_vm_destroy(fd, local_cfg.vm);
>   			}
>   		}
> -		for (n = 0; n < QLEN; n++)
> +		for (n = 0; n < qlen; n++)
>   			gem_close(fd, batches[n].handle);
>   		if (flags & FDS) {
>   			for (n = 0; n < 64; n++)