Speedup InitialSessionState..cctor() #14283
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iSazonov
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CL-Performance
| // with no content. So create a scratch file and test on that. | ||
| string dtAppLockerTestFileContents = AppLockerTestFileContents + DateTime.Now; | ||
| string dtAppLockerTestFileContents = AppLockerTestFileContents + DateTime.UtcNow.Ticks; | ||
| IO.File.WriteAllText(testPathScript, dtAppLockerTestFileContents); |
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It seems the file name does not depend on the DateTime, but rather the file contents. So maybe we want to keep human date format
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The file is created for automatic testing - no humans see and read the file.
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no humans see and read the file.
Perhaps it is for debugging purposes.
Actually, if no humans see the file do we require the datetime to be written in any form at all?
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I don't know. I am only resolving the perf issue. I can only guess it is how AppLocker works. Perhaps @TravisEz13 or @PaulHigin could add more information.
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@TravisEz13 and @PaulHigin, can you please comment on whether we need DateTime to be added to the file content at all?
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The DateTime was included to add some randomness to the file contents. I think we still need it, but could change it to some other random value if computing it is quicker than DateTime.
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@iSazonov Maybe replacing DateTime.Now.Ticks with Environemnt.TickCount?
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@daxian-dbw I have no objections. I see Environment.TickCount64 - maybe use it?
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That sounds fine to me, go ahead.
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Done. The PR description has been updated too.
| // AppLocker fails when you try to check a policy on a file | ||
| // with no content. So create a scratch file and test on that. | ||
| string dtAppLockerTestFileContents = AppLockerTestFileContents + DateTime.Now; | ||
| string dtAppLockerTestFileContents = AppLockerTestFileContents + DateTime.UtcNow.Ticks; |
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| string dtAppLockerTestFileContents = AppLockerTestFileContents + DateTime.UtcNow.Ticks; | |
| string dtAppLockerTestFileContents = AppLockerTestFileContents + DateTime.UtcNow.ToString("u"); |
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I took real world measurements using PerfView 😋
It seems my suggested change is not much of an improvement, I measured 8ms for the code line.
I also measured the original code line and it was 14ms, same as your measurement.
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DateTime.UtcNow is more fast - it does not read current user time zone and does not convert to local time.
Is this a release build? Running a microbenchmark, |
Yes, it is release build. And it is startup scenario - cold start (.Net runtime loads Calendar data from OS and initializes internal structures - you can see this in attached trace file.). If you run BenchmarkDotNet it is warm start. |
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🎉 Handy links: |
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PR Summary
At startup we create a temp file with name based on
Datetime.Now.ToString().It is very slow - ~14ms.
We have no need to use human date format for the temp file.
The fix is to use
Datetime.UtcNow().Ticks.ToString()Environment.TickCount64:Environment.TickCount64is significantly faster Datetime.Now() - it is intrinsic and no need to evaluate local time.Perf win is ~10-30 ms.
Before
After
PR Context
Tracking issue #14268
PR Checklist
.h,.cpp,.cs,.ps1and.psm1files have the correct copyright headerWIP:or[ WIP ]to the beginning of the title (theWIPbot will keep its status check atPendingwhile the prefix is present) and remove the prefix when the PR is ready.