Small times may be given to time conversion if GPU clocks are used to
accumulate elapsed time. Because HSA APIs deal in absolute time this
leads to large conversion offsets of order system uptime. Variation
in relative clock ratio estimation may be amplified in this case,
destroying elapsed time measurements.
This patch fixes the relative clock ratio used for times which predate
the call to hsa_init. This correlates errors in such times allowing
the elapsed time to be correctly computed.
The effective maximum system uptime before elapsed time conversion becomes
inaccurate is ~3.5 months. GPU event timestamps are good for process uptime
of ~3.5 months. These are limited by double's mantissa precision.
Change-Id: I48752ff354920439d91016d6f2b0c8ddfa60b445
Sean Keely
6e2a056e1b