Add gem_fence_thrash test

This is a test case that overcommits fence registers between threads, which
are copying from one fenced bo to another. In earlier versions of the driver
this would cause excessive spinning as the first inactive (i.e. not in use
by the GPU) would be used to service the next page. After all the fence
registers had been allocated, in effect only the very first fence would then
be used for all subsequent faults.

0 files changed, 0 insertions, 0 deletions