On 29/02/16 10:53, Chris Wilson wrote:
On Mon, Feb 29, 2016 at 10:45:34AM +0000, Tvrtko Ursulin wrote:
This ok?
"""
One unexplained result is with "gem_latency -n 0" (dispatching
empty batches) which shows 5% more throughput, 8% less CPU time,
25% better producer and consumer latencies, but 15% higher
dispatch latency which looks like a possible measuring artifact.
"""
I doubt it is a measuring artefact since throughput = 1/(dispatch +
latency + test overhead), and the dispatch latency here is larger than
the wakeup latency and so has greater impact on throughput in this
scenario.
I don't follow you, if dispatch latency has larger effect on throughput
how to explain the increase and still better throughput?
I see in gem_latency this block:
measure_latency(p, &p->latency);
igt_stats_push(&p->dispatch, *p->last_timestamp - start);
measure_latency waits for the batch to complete and then dispatch
latency uses p->last_timestamp which is something written by the GPU and
not a CPU view of the latency ?
Regards,
Tvrtko
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