aace62f6d3
Linux 6.2 and up (commit [f1f1f2569901ec5b9d425f2e91c09a0e320768f3][1]) provides a fast path for the number of open files for the process. From the [Linux docs][2]: > The number of open files for the process is stored in 'size' member of > `stat()` output for /proc/<pid>/fd for fast access. [1]:f1f1f25699[2]: https://docs.kernel.org/filesystems/proc.html#proc-pid-fd-list-of-symlinks-to-open-files This patch adds a fast-path for Kernels that support this, and falls back to the slow path if the Size fields is zero. Comparing on a Fedora 38 (kernel 6.2.9-300.fc38.x86_64): Before/After: go test -bench ^BenchmarkGetTotalUsedFds$ -run ^$ ./pkg/fileutils/ BenchmarkGetTotalUsedFds 57264 18595 ns/op 408 B/op 10 allocs/op BenchmarkGetTotalUsedFds 370392 3271 ns/op 40 B/op 3 allocs/op Note that the slow path has 1 more file-descriptor, due to the open file-handle for /proc/<pid>/fd during the calculation. Signed-off-by: Sebastiaan van Stijn <github@gone.nl> (cherry picked from commitec79d0fc05) Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
52 lines
1.4 KiB
Go
52 lines
1.4 KiB
Go
package fileutils
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import (
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"context"
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"fmt"
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"io"
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"os"
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"github.com/containerd/containerd/log"
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"golang.org/x/sys/unix"
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)
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// GetTotalUsedFds Returns the number of used File Descriptors by
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// reading it via /proc filesystem.
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func GetTotalUsedFds() int {
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name := fmt.Sprintf("/proc/%d/fd", os.Getpid())
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// Fast-path for Linux 6.2 (since [f1f1f2569901ec5b9d425f2e91c09a0e320768f3]).
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// From the [Linux docs]:
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//
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// "The number of open files for the process is stored in 'size' member of
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// stat() output for /proc/<pid>/fd for fast access."
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//
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// [Linux docs]: https://docs.kernel.org/filesystems/proc.html#proc-pid-fd-list-of-symlinks-to-open-files:
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// [f1f1f2569901ec5b9d425f2e91c09a0e320768f3]: https://github.com/torvalds/linux/commit/f1f1f2569901ec5b9d425f2e91c09a0e320768f3
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var stat unix.Stat_t
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if err := unix.Stat(name, &stat); err == nil && stat.Size > 0 {
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return int(stat.Size)
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}
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f, err := os.Open(name)
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if err != nil {
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log.G(context.TODO()).WithError(err).Error("Error listing file descriptors")
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return -1
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}
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defer f.Close()
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var fdCount int
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for {
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names, err := f.Readdirnames(100)
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fdCount += len(names)
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if err == io.EOF {
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break
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} else if err != nil {
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log.G(context.TODO()).WithError(err).Error("Error listing file descriptors")
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return -1
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}
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}
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// Note that the slow path has 1 more file-descriptor, due to the open
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// file-handle for /proc/<pid>/fd during the calculation.
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return fdCount
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}
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