We are calling pm_qos from some of our drivers. One concern is that
each call of pm_qos_update_requirement() iterates through the client
list and strcmp the client names. It could be slow. A proposal is
that pm_qos provides handles that can be used on
pm_qos_update_requirement().
For measurement purposes, I added get/put interfaces to
acquire/release the handles and a new pm_qos_update_requirement
function that bypasses the iteration and strcmp. Here are some
collected data:
How many clock cycles does pm_qos_update_requirement take?
when there is one client on this qos_class:
using handle using name using handle/using name
avg 252.4 400.4 63%
when there are 5 clients on this qos_class:
using handle using name using handle/using name
avg 407.6 644.8 63%
when there are 10 clients on this qos_class:
using handle using name using handle/using name
avg 582.4 938.4 62%
Given the time differences, it seems worthwhile to add handles.
~Ai
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