When a timeout of zero is specified, the caller is only interested in
the fence status.
In the current implementation, dma_fence_default_wait will always call
schedule_timeout() at least once for an unsignaled fence. This adds a
significant overhead to a fence status query.
Avoid this overhead by returning early if a zero timeout is specified.
v2: move early return after enable_signaling
Signed-off-by: Andres Rodriguez <andresx7@xxxxxxxxx>
---
If I'm understanding correctly, I don't think we need to register the
default wait callback. But if that isn't the case please let me know.
This patch has the same perf improvements as v1.
drivers/dma-buf/dma-fence.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 0918d3f..57da14c 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -402,6 +402,11 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
}
}
+ if (!timeout) {
+ ret = 0;
+ goto out;
+ }
+
cb.base.func = dma_fence_default_wait_cb;
cb.task = current;
list_add(&cb.base.node, &fence->cb_list);
--
2.9.3
