[Bug 60462] New: NtPowerInformation(ProcessorInformation) opens two cpufreq files per CPU on every call

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=60462

            Bug ID: 60462
           Summary: NtPowerInformation(ProcessorInformation) opens two
                    cpufreq files per CPU on every call
           Product: Wine
           Version: unspecified
          Hardware: aarch64
                OS: Android
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
  Target Milestone: ---

NtPowerInformation(ProcessorInformation) (dlls/ntdll/unix/system.c, master
63f62f7cd696, lines 4682-4730) opens
/sys/devices/system/cpu/cpuN/cpufreq/cpuinfo_max_freq and scaling_max_freq for
every CPU on every call, with no caching (CurrentMhz is set to MaxMhz anyway).

Some games call CallNtPowerInformation(ProcessorInformation) every frame. Age
of Empires IV does, about 45 times per second in a match. On an 8-core
Snapdragon 8 Gen 2 (Proton 11 ARM64EC through GameNative, Android) one call
took 228.5 us on average (200 calls, game idle at its menu), and in a late-game
replay the call took 11 % of the game's main thread. Answering repeat calls
from a cache for 250 ms (done outside Wine, in the emulator layer, as a test)
brought that to 1.7 % and gave about +0.5 FPS.

Possible fix: read cpuinfo_max_freq once, and cache scaling_max_freq for a
short time (it can change with power and thermal policy, so not forever).

See also bug 58397: battery state queries through NtPowerInformation also read
sysfs on every call.

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