On 30/11/15 17:11, Chris Wilson wrote:
On Mon, Nov 30, 2015 at 06:53:06PM +0200, Mika Kuoppala wrote:
Some operations that happen in ringbuffer, like flushing,
can take significant amounts of time. After some intense
shader tests, the PIPE_CONTROL with flush can apparently last
longer time than what is our hangcheck tick (1500ms). If
this happens twice in a row, even with subsequent batches,
the hangcheck score decaying mechanism can't cope and
hang is declared.
Strip out actual head checking to a separate function and if
actual head has not moved, check if it is lingering inside the
ringbuffer as opposed to batch. If so, treat it as if it would be
inside loop to only slightly increment the hangcheck score.
The PIPE_CONTROL in the ring after the batch, is equivalent to the batch
performing its own PIPE_CONTROL as the last instruction. It does not
make sense to distinguish the two.
-Chris
It's equivalent in terms of outcome, but not when checking what's
happening. The driver controls insertion of PIPE_CONTROLs in the ring,
but not in batches. If execution is at the ring level, we know it's
running instructions that the driver put there, and we know that it
*will* then progress to the next batch (assuming the hardware's not
stuck). OTOH if execution is inside a batch then we don't know what
sequence of instructions it's running, and we can't guarantee that the
batch will ever terminate. So, a reduced penalty if executing
driver-supplied code makes sense.
.Dave.
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