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71029cea2d
This updates all source files to use a new standard header for copyright and license declaration. Notably, copyright no longer includes a date, and we now use the standard SPDX-License-Identifier header. This commit was done almost entirely mechanically with perl, and then some minimal manual fixes. Updates #6865 Signed-off-by: Will Norris <will@tailscale.com>
42 lines
818 B
Go
42 lines
818 B
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package metrics
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import (
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"io/fs"
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"sync"
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"go4.org/mem"
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"tailscale.com/util/dirwalk"
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)
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// counter is a reusable counter for counting file descriptors.
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type counter struct {
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n int
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// cb is the (*counter).count method value. Creating it allocates,
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// so we have to save it away and use a sync.Pool to keep currentFDs
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// amortized alloc-free.
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cb func(name mem.RO, de fs.DirEntry) error
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}
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var counterPool = &sync.Pool{New: func() any {
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c := new(counter)
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c.cb = c.count
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return c
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}}
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func (c *counter) count(name mem.RO, de fs.DirEntry) error {
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c.n++
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return nil
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}
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func currentFDs() int {
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c := counterPool.Get().(*counter)
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defer counterPool.Put(c)
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c.n = 0
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dirwalk.WalkShallow(mem.S("/proc/self/fd"), c.cb)
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return c.n
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}
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