[Intel-gfx] [PATCH i-g-t v4] benchmarks/gem_wsim: Command submission workload simulator

[Chris Wilson]

On Thu, Apr 20, 2017 at 01:29:11PM +0100, Tvrtko Ursulin wrote:
> +static void
> +alloc_step_batch(struct workload *wrk, struct w_step *w, struct w_step_eb *b,
> +		 enum intel_engine_id engine, unsigned int flags)
> +{
> +	unsigned int bb_i, j = 0;
> +
> +	b->obj[j].handle = gem_create(fd, 4096);
> +	b->obj[j].flags = EXEC_OBJECT_WRITE;
> +	j++;
> +
> +	if (flags & SEQNO) {
> +		b->obj[j].handle = wrk->status_page_handle;
> +		j++;
> +	}
> +
> +	bb_i = j++;
> +	b->bb_sz = get_bb_sz(w->duration.max);
> +	b->bb_handle = b->obj[bb_i].handle = gem_create(fd, b->bb_sz);
> +	terminate_bb(w, b, engine, flags);
> +
> +	igt_assert(w->dependency <= 0);
> +	if (w->dependency) {
> +		int dep_idx = w->idx + w->dependency;
> +
> +		igt_assert(dep_idx >= 0 && dep_idx < wrk->nr_steps);
> +		igt_assert(wrk->steps[dep_idx].type == BATCH);
> +
> +		b->obj[j].handle = b->obj[bb_i].handle;
> +		bb_i = j;
> +		b->obj[j - 1].handle = wrk->steps[dep_idx].b[0].obj[0].handle;
> +		j++;
> +
> +		if (wrk->steps[dep_idx].b[1].obj[0].handle) {
> +			b->obj[j].handle = b->obj[bb_i].handle;
> +			bb_i = j;
> +			b->obj[j - 1].handle =
> +					wrk->steps[dep_idx].b[1].obj[0].handle;
> +			j++;
> +		}
> +	}
> +
> +	if (flags & SEQNO) {
> +		b->reloc.presumed_offset = -1;

So as I understand it, you are caching the execbuf/obj/reloc for the
workload and then may reissue later with different seqno on different
rings? In which case we have a problem as the kernel will write back the
updated offsets to b->reloc.presumed_offset and b->obj[].offset and in
future passes they will match and the seqno write will go into the wrong
slot (if it swaps rings).

You either want to reset presumed_offset=-1 each time, or better for all
concerned write the correct address alongside the seqno (which also
enables NORELOC).

Delta incoming.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre