[Mesa-dev] [PATCH 13/17] i965: Use a separate state buffer, but avoid changing flushing behavior.

[Chris Wilson]

Quoting Kenneth Graunke (2017-09-06 01:09:46)
> However, this patch tries to retain the original flushing behavior - it
> adds the amount of batch and state space together, as if they were still
> co-existing in a single buffer.  The hope is to flush at the same time
> as before.  This is necessary to avoid provoking bugs caused by broken
> batch wrap handling (which we'll fix shortly).  It also avoids suddenly
> increasing the size of the batch (due to state not taking up space),
> which could have a significant performance impact.  We'll tune it later.

Note that there is also another potential perf impact from changing
batch sizes, sometimes the smaller batch and lower latency is critical
to keeping the GPU busy. (Not often an issue for us!)
-Chris