feat: improve ProcFDUsage performance#189
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andrewkroh merged 1 commit intoelastic:masterfrom Jun 6, 2025
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ioutil.ReadDir calls stat on every directory entry. These calls are not required
to count the number of file descriptors.
For a process with many open file descriptors this can be costly.
In a local benchmark on a directory with 10k files, we observe the following
improvement by using (*os.File).Readdir directly:
```
goos: linux
goarch: amd64
pkg: github.com/elastic/gosigar
cpu: Intel(R) Xeon(R) CPU @ 2.80GHz
│ old.txt │ new.txt │
│ sec/op │ sec/op vs base │
GetDirEntryCount-24 23.874m ± 0% 2.967m ± 0% -87.57% (p=0.000 n=25)
│ old.txt │ new.txt │
│ B/op │ B/op vs base │
GetDirEntryCount-24 3310.4Ki ± 0% 729.4Ki ± 0% -77.97% (p=0.000 n=25)
│ old.txt │ new.txt │
│ allocs/op │ allocs/op vs base │
GetDirEntryCount-24 30.03k ± 0% 10.02k ± 0% -66.62% (p=0.000 n=25)
```
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ioutil.ReadDir calls stat on every directory entry. These calls are not required
to count the number of file descriptors.
For a process with many open file descriptors this can be costly.
In a local benchmark on a directory with 10k files, we observe the following improvement by using (*os.File).Readdirnames directly: