> Now what seems to be asked for is that something akin to the > android WAKE_LOCK_IDLE "thing". > > Last night I gave some thought to this. One could put a boolean > or bit mask flag into the aggregated value that when polled the > poller could know to not go to any lower performing state or > kick the system into higher performance states. Setting the > flag would only happen from kernel API's and no notification > trees would be called as it gets toggled. (that would kill fast > path performance) Android WAKE_LOCK_IDLE is a very coarse setting. It does not take advantage of the multiple performance states with their corresponding latency values. WAKE_LOCK_IDLE potentially disallows some low performance states when their latencies may be quite acceptable. In contrast, an integer setting would allow a better match between the requested latency value and the appropriate low power states. pm_qos already provides the integer setting. IMO, the question is how to enable hot-path flow through pm_qos... > But as I thought about it it became clear the correct behavior > is really a function of the parameter class. If the parameter > is cpu_dma_latency then the flag would be used to simply disable > CPUIDLE from doing any high latency idle states. However; such > a flag for network bandwidth (a flag hit in some fast code path) > shouldn't be telling the NIC to kick up from 100Mbs to 1000Mbs > or go back. > > So what would a fast path pm-qos parameter look like and how > would it be used, outside of CPUIDLE? > Stating it in another way: the correct hot path behavior for each parameter class is dependent on what the parameter class is. To accommodate this, we could add a hot_path_fn in struct pm_qos_object. It specifies the hot path behavior for the parameter class. In the hot path flow, update_target() will call pm_qos_array[pm_qos_class]->hot_path_fn() instead of the notifier chain. With regards to NIC cards, I'm not sure what hot_path_fn() would perform. Maybe the default hot_path_fn for PM_QOS_NETWORK_THROUGHPUT does nothing; the platform code or NIC card code can register a different hot_path_fn. ~Ai _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
