index-parser: get the time in a cheaper way #1798
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UtcNow spends a lot of time getting a very precise system time, including leap seconds and interpolation through QueryPerformanceCounter. Use Environment.TickCount (milliseconds since boot) instead, since that just retrieves a value in shared memory that the kernel keeps up to date. This value is still suitable for controlling how much log output index parsing produces. This UtcNow call consumes 15% of the time under GitIndexParser.ParseIndex. See https://github.com/dotnet/runtime/blob/master/src/libraries/System.Private.CoreLib/src/System/DateTime.Windows.cs.
derrickstolee
approved these changes
Feb 13, 2023
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DateTime.UtcNow spends a lot of time getting a very precise system time, including leap seconds and interpolation through
QueryPerformanceCounter.
Use Environment.TickCount (milliseconds since boot) instead, since that just retrieves a value in shared memory that the kernel keeps up to date. This value is still suitable for controlling how much log output index parsing produces.
This UtcNow call consumes 15% of the time under GitIndexParser.ParseIndex.
See the UtcNow implementation at:
See https://github.com/dotnet/runtime/blob/master/src/libraries/System.Private.CoreLib/src/System/DateTime.Windows.cs.