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portlist: use win32 calls instead of running netstat process [windows]

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Turns out using win32 instead of shelling out to child processes is a
bit faster:

    name                  old time/op    new time/op    delta
    GetListIncremental-4     278ms ± 2%       0ms ± 7%  -99.93%  (p=0.000 n=8+10)

    name                  old alloc/op   new alloc/op   delta
    GetListIncremental-4     238kB ± 0%       9kB ± 0%  -96.12%  (p=0.000 n=10+8)

    name                  old allocs/op  new allocs/op  delta
    GetListIncremental-4     1.19k ± 0%     0.02k ± 0%  -98.49%  (p=0.000 n=10+10)

Fixes #3876 (sadly)

Change-Id: I1195ac5de21a8a8b3cdace5871d263e81aa27e91
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2022-10-23 22:07:25 -07:00
committed by Brad Fitzpatrick
parent 527741d41f
commit 35bee36549
3 changed files with 102 additions and 29 deletions
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portlist/netstat_exec.go
+1 -11
View File
@@ -15,22 +15,12 @@ import (
"strings"
)
var osHideWindow func(*exec.Cmd) // non-nil on Windows; see portlist_windows.go
// hideWindow returns c. On Windows it first sets SysProcAttr.HideWindow.
func hideWindow(c *exec.Cmd) *exec.Cmd {
if osHideWindow != nil {
osHideWindow(c)
}
return c
}
func appendListeningPortsNetstat(base []Port, arg string) ([]Port, error) {
exe, err := exec.LookPath("netstat")
if err != nil {
return nil, fmt.Errorf("netstat: lookup: %v", err)
}
output, err := hideWindow(exec.Command(exe, arg)).Output()
output, err := exec.Command(exe, arg).Output()
if err != nil {
xe, ok := err.(*exec.ExitError)
stderr := ""