diff mbox

[i-g-t,1/2] lib: Spin fast, retire early

Message ID 20180620115706.4087-1-chris@chris-wilson.co.uk (mailing list archive)
State New, archived
Headers show

Commit Message

Chris Wilson June 20, 2018, 11:57 a.m. UTC 
When using the pollable spinner, we often want to use it as a means of
ensuring the task is running on the GPU before switching to something
else. In which case we don't want to add extra delay inside the spinner,
but the current 1000 NOPs add on order of 5us, which is often larger
than the target latency.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Antonio Argenziano <antonio.argenziano@intel.com>
---
 lib/igt_dummyload.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Joonas Lahtinen June 20, 2018, 12:11 p.m. UTC | #1 
Quoting Chris Wilson (2018-06-20 14:57:05)
> When using the pollable spinner, we often want to use it as a means of
> ensuring the task is running on the GPU before switching to something
> else. In which case we don't want to add extra delay inside the spinner,
> but the current 1000 NOPs add on order of 5us, which is often larger
> than the target latency.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Antonio Argenziano <antonio.argenziano@intel.com>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Regards, Joonas
diff mbox

Patch

diff --git a/lib/igt_dummyload.c b/lib/igt_dummyload.c
index 3809b4e61..d73b4abd5 100644
--- a/lib/igt_dummyload.c
+++ b/lib/igt_dummyload.c
@@ -77,6 +77,7 @@  fill_reloc(struct drm_i915_gem_relocation_entry *reloc,
 
 #define OUT_FENCE	(1 << 0)
 #define POLL_RUN	(1 << 1)
+#define SPIN_FAST       (1 << 2)
 
 static int
 emit_recursive_batch(igt_spin_t *spin, int fd, uint32_t ctx, unsigned engine,
@@ -205,7 +206,8 @@  emit_recursive_batch(igt_spin_t *spin, int fd, uint32_t ctx, unsigned engine,
 	 * between function calls, that appears enough to keep SNB out of
 	 * trouble. See https://bugs.freedesktop.org/show_bug.cgi?id=102262
 	 */
-	batch += 1000;
+	if (!(flags & SPIN_FAST))
+		batch += 1000;
 
 	/* recurse */
 	r = &relocs[obj[BATCH].relocation_count++];
@@ -362,7 +364,7 @@  igt_spin_batch_new_fence(int fd, uint32_t ctx, unsigned engine)
 igt_spin_t *
 __igt_spin_batch_new_poll(int fd, uint32_t ctx, unsigned engine)
 {
-	return ___igt_spin_batch_new(fd, ctx, engine, 0, POLL_RUN);
+	return ___igt_spin_batch_new(fd, ctx, engine, 0, POLL_RUN | SPIN_FAST);
 }
 
 /**