[igt-dev] [PATCH i-g-t 5/7] gem_wsim: Make batches preemptable by default

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

MI_NOOP cannot be preempted which means up to now gem_wsim workloads were
preemptable on batch buffer granularity only.

Add MI_ARB_CHK every 100us so the new default is mid-batch preemption.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 benchmarks/gem_wsim.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/benchmarks/gem_wsim.c b/benchmarks/gem_wsim.c
index 24f518a7770f..f60c086a3f1e 100644
--- a/benchmarks/gem_wsim.c
+++ b/benchmarks/gem_wsim.c
@@ -683,6 +683,25 @@ static unsigned long get_bb_sz(unsigned int duration)
 		     nop_calibration_us, sizeof(uint32_t));
 }
 
+static void
+init_bb(struct w_step *w, unsigned int flags)
+{
+	/* Preemption point every 100us. */
+	const unsigned int arb_period = get_bb_sz(100) / sizeof(uint32_t);
+	unsigned int i;
+	uint32_t *ptr;
+
+	gem_set_domain(fd, w->bb_handle,
+		       I915_GEM_DOMAIN_WC, I915_GEM_DOMAIN_WC);
+
+	ptr = gem_mmap__wc(fd, w->bb_handle, 0, w->bb_sz, PROT_WRITE);
+
+	for (i = arb_period; i < w->bb_sz / sizeof(uint32_t); i += arb_period)
+		ptr[i] = 0x5 << 23; /* MI_ARB_CHK */
+
+	munmap(ptr, w->bb_sz);
+}
+
 static void
 terminate_bb(struct w_step *w, unsigned int flags)
 {
@@ -836,6 +855,7 @@ alloc_step_batch(struct workload *wrk, struct w_step *w, unsigned int flags)
 
 	w->bb_sz = get_bb_sz(w->duration.max);
 	w->bb_handle = w->obj[j].handle = gem_create(fd, w->bb_sz);
+	init_bb(w, flags);
 	terminate_bb(w, flags);
 
 	if (flags & SEQNO) {
-- 
2.17.1