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db2cc393af
This is similar to the golang.org/x/tools/internal/fastwalk I'd
previously written but not recursive and using mem.RO.
The metrics package already had some Linux-specific directory reading
code in it. Move that out to a new general package that can be reused
by portlist too, which helps its scanning of all /proc files:
name old time/op new time/op delta
FindProcessNames-8 2.79ms ± 6% 2.45ms ± 7% -12.11% (p=0.000 n=10+10)
name old alloc/op new alloc/op delta
FindProcessNames-8 62.9kB ± 0% 33.5kB ± 0% -46.76% (p=0.000 n=9+10)
name old allocs/op new allocs/op delta
FindProcessNames-8 2.25k ± 0% 0.38k ± 0% -82.98% (p=0.000 n=9+10)
Change-Id: I75db393032c328f12d95c39f71c9742c375f207a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
43 lines
907 B
Go
43 lines
907 B
Go
// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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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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