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Merge pull request #45856 from thaJeztah/24.0_backport_improve_fd_count
[24.0 backport] pkg/fileutils: GetTotalUsedFds: reduce allocations
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Original file line number | Diff line number | Diff line change |
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package fileutils | ||
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import ( | ||
"context" | ||
"fmt" | ||
"io" | ||
"os" | ||
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"github.com/containerd/containerd/log" | ||
"golang.org/x/sys/unix" | ||
) | ||
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// GetTotalUsedFds Returns the number of used File Descriptors by | ||
// reading it via /proc filesystem. | ||
func GetTotalUsedFds() int { | ||
name := fmt.Sprintf("/proc/%d/fd", os.Getpid()) | ||
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// Fast-path for Linux 6.2 (since [f1f1f2569901ec5b9d425f2e91c09a0e320768f3]). | ||
// From the [Linux docs]: | ||
// | ||
// "The number of open files for the process is stored in 'size' member of | ||
// stat() output for /proc/<pid>/fd for fast access." | ||
// | ||
// [Linux docs]: https://docs.kernel.org/filesystems/proc.html#proc-pid-fd-list-of-symlinks-to-open-files: | ||
// [f1f1f2569901ec5b9d425f2e91c09a0e320768f3]: https://github.com/torvalds/linux/commit/f1f1f2569901ec5b9d425f2e91c09a0e320768f3 | ||
var stat unix.Stat_t | ||
if err := unix.Stat(name, &stat); err == nil && stat.Size > 0 { | ||
return int(stat.Size) | ||
} | ||
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f, err := os.Open(name) | ||
if err != nil { | ||
log.G(context.TODO()).WithError(err).Error("Error listing file descriptors") | ||
return -1 | ||
} | ||
defer f.Close() | ||
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var fdCount int | ||
for { | ||
names, err := f.Readdirnames(100) | ||
fdCount += len(names) | ||
if err == io.EOF { | ||
break | ||
} else if err != nil { | ||
log.G(context.TODO()).WithError(err).Error("Error listing file descriptors") | ||
return -1 | ||
} | ||
} | ||
// Note that the slow path has 1 more file-descriptor, due to the open | ||
// file-handle for /proc/<pid>/fd during the calculation. | ||
return fdCount | ||
} |
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