On 1/22/21 8:21 AM, Steven Price wrote:
On 21/01/2021 17:04, Lukasz Luba wrote:
The simple_ondemand devfreq governor uses two thresholds to decide about the frequency change: upthreshold, downdifferential. These two tunable change the behavior of the governor decision, e.g. how fast to increase the frequency or how rapidly limit the frequency. This patch adds needed governor data with thresholds values gathered experimentally in different workloads.
Signed-off-by: Lukasz Luba lukasz.luba@arm.com
Hi all,
This patch aims to improve the panfrost performance in various workloads, (benchmarks, games). The simple_ondemand devfreq governor supports tunables to tweak the behaviour of the internal algorithm. The default values for these two thresholds (90 and 5) do not work well with panfrost. These new settings should provide good performance, short latency for rising the frequency due to rapid workload change and decent freq slow down when the load is decaying. Based on frequency change statistics, gathered during experiments, all frequencies are used, depending on the load. This provides some power savings (statistically). The highest frequency is also used when needed.
Example glmark2 results:
- freq fixed to max: 153
- these new thresholds values (w/ patch): 151
- default governor values (w/o patch): 114
It would be good to state which platform this is on as this obviously can vary depending on the OPPs available.
Sorry about that. It was Rock Pi 4B and I have mesa 20.2.4.
Of course the real fix here would be to improve the utilisation of the GPU[1] so we actually hit the 90% threshold more easily (AFAICT kbase uses the default 90/5 thresholds), but this seems like a reasonable change for now.
Agree, improving the scheduler would be the best option. I'll have a look at that patch and why it got this 10% lower performance. Maybe I would find something during testing.
Reviewed-by: Steven Price steven.price@arm.com
Thank you for the review. I guess this patch would go through drm tree?
Regards, Lukasz
Thanks,
Steve
[1] When I get some time I need to rework the "queue jobs on the hardware"[2] patch I posted ages ago. Last time it actually caused a performance regression though...
[2] https://lore.kernel.org/r/20190816093107.30518-2-steven.price%40arm.com