Testing with Crimson 16.11.5
I used this test file ps test.blend from ⚓ T50082 OpenCL issue and motion blur (AMD 7870 Pitcairn)
Render time with 16.11.3 is 15.28 seconds
Render time with 16.11.5 is 53.78 seconds.
Difference is 40 seconds ! That is very noticable performance drop.
Memory usage and memory peak are the same.