[igt-dev] [PATCH i-g-t] i915/gem_exec_parse: Switch to a fixed timeout for basic-allocations

[Chris Wilson]

basic-allocations was written to demonstrate a flaw in our continual
reallocation of cmdparser shadow bo, largely fixed by keeping a small
cache of bo of different lengths (to speed up the search for the correct
sized bo). We only care enough to exercise the slowdown by submitting
lots of execbufs, and can see the effect of bo caching on the rate, so
replace the fixed number of iterations with a timeout and count how many
batches we could submit instead.

Similarly, we now do not need to wait for all of our queue to complete
as we can tell the kernel to drop the queue instead.

References: https://bugs.freedesktop.org/show_bug.cgi?id=107936
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 tests/i915/gem_exec_parse.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/tests/i915/gem_exec_parse.c b/tests/i915/gem_exec_parse.c
index b653b1bdc..62e8d0a51 100644
--- a/tests/i915/gem_exec_parse.c
+++ b/tests/i915/gem_exec_parse.c
@@ -303,15 +303,15 @@ test_lri(int fd, uint32_t handle, struct test_lri *test)
 
 static void test_allocations(int fd)
 {
-	uint32_t bbe = MI_BATCH_BUFFER_END;
+	const uint32_t bbe = MI_BATCH_BUFFER_END;
 	struct drm_i915_gem_execbuffer2 execbuf;
 	struct drm_i915_gem_exec_object2 obj[17];
-	int i, j;
+	unsigned long count;
 
 	intel_require_memory(2, 1ull<<(12 + ARRAY_SIZE(obj)), CHECK_RAM);
 
 	memset(obj, 0, sizeof(obj));
-	for (i = 0; i < ARRAY_SIZE(obj); i++) {
+	for (int i = 0; i < ARRAY_SIZE(obj); i++) {
 		uint64_t size = 1ull << (12 + i);
 
 		obj[i].handle = gem_create(fd, size);
@@ -322,17 +322,21 @@ static void test_allocations(int fd)
 
 	memset(&execbuf, 0, sizeof(execbuf));
 	execbuf.buffer_count = 1;
-	for (j = 0; j < 16384; j++) {
-		igt_progress("allocations ", j, 16384);
-		i = rand() % ARRAY_SIZE(obj);
+
+	count = 0;
+	igt_until_timeout(20) {
+		int i = rand() % ARRAY_SIZE(obj);
 		execbuf.buffers_ptr = to_user_pointer(&obj[i]);
 		execbuf.batch_start_offset = (rand() % (1ull<<i)) << 12;
 		execbuf.batch_start_offset += 64 * (rand() % 64);
 		execbuf.batch_len = (1ull<<(12+i)) - execbuf.batch_start_offset;
 		gem_execbuf(fd, &execbuf);
+		count++;
 	}
+	igt_info("Submitted %lu execbufs\n", count);
+	igt_drop_caches_set(fd, DROP_RESET_ACTIVE); /* Cancel the queued work */
 
-	for (i = 0; i < ARRAY_SIZE(obj); i++) {
+	for (int i = 0; i < ARRAY_SIZE(obj); i++) {
 		gem_sync(fd, obj[i].handle);
 		gem_close(fd, obj[i].handle);
 	}
-- 
2.20.1