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portlist: reduce CPU parsing portlist 

Avoid splitting fields in the common case. Field splitting was 84% of
the overall CPU.

name          old time/op    new time/op    delta
ParsePorts-6    33.3ms ± 2%     6.3ms ± 4%  -80.97%  (p=0.000 n=9+10)

name          old alloc/op   new alloc/op   delta
ParsePorts-6      520B ±79%      408B ± 0%  -21.49%  (p=0.046 n=10+8)

name          old allocs/op  new allocs/op  delta
ParsePorts-6      7.00 ± 0%      7.00 ± 0%     ~     (all equal)

Updates tailscale/corp#2566

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2021-09-12 19:49:37 -07:00 committed by Brad Fitzpatrick
parent 64e9ce8df1
commit 5a9d977c78
2 changed files with 79 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
portlist/portlist_linux.go
View File

@ -43,8 +43,6 @@ func listPorts() (List, error) {
l := []Port{}
for _, fname := range sockfiles {
proto := strings.TrimSuffix(filepath.Base(fname), "6")
// Android 10+ doesn't allow access to this anymore.
// https://developer.android.com/about/versions/10/privacy/changes#proc-net-filesystem
// Ignore it rather than have the system log about our violation.
@ -64,7 +62,7 @@ func listPorts() (List, error) {
defer f.Close()
r := bufio.NewReader(f)
ports, err := parsePorts(r, proto)
ports, err := parsePorts(r, filepath.Base(fname))
if err != nil {
return nil, fmt.Errorf("parsing %q: %w", fname, err)
}
@ -74,7 +72,9 @@ func listPorts() (List, error) {
return l, nil
}
func parsePorts(r *bufio.Reader, proto string) ([]Port, error) {
// fileBase is one of "tcp", "tcp6", "udp", "udp6".
func parsePorts(r *bufio.Reader, fileBase string) ([]Port, error) {
proto := strings.TrimSuffix(fileBase, "6")
var ret []Port
// skip header row
@ -85,6 +85,11 @@ func parsePorts(r *bufio.Reader, proto string) ([]Port, error) {
fields := make([]mem.RO, 0, 20) // 17 current fields + some future slop
wantRemote := mem.S(v4Any)
if strings.HasSuffix(fileBase, "6") {
wantRemote = mem.S(v6Any)
}
var inoBuf []byte
for err == nil {
line, err := r.ReadSlice('\n')
@ -95,22 +100,29 @@ func parsePorts(r *bufio.Reader, proto string) ([]Port, error) {
return nil, err
}
if i := fieldIndex(line, 2); i == -1 ||
!mem.HasPrefix(mem.B(line).SliceFrom(i), wantRemote) {
// Fast path for not being a listener port.
continue
}
// sl local rem ... inode
fields = mem.AppendFields(fields[:0], mem.B(line))
local := fields[1]
rem := fields[2]
inode := fields[9]
if !rem.Equal(wantRemote) {
// not a "listener" port
continue
}
// If a port is bound to localhost, ignore it.
// TODO: localhost is bigger than 1 IP, we need to ignore
// more things.
if mem.HasPrefix(local, mem.S(v4Localhost)) || mem.HasPrefix(local, mem.S(v6Localhost)) {
continue
}
if !rem.Equal(mem.S(v4Any)) && !rem.Equal(mem.S(v6Any)) {
// not a "listener" port
continue
}
// Don't use strings.Split here, because it causes
// allocations significant enough to show up in profiles.
@ -240,3 +252,26 @@ func foreachPID(fn func(pidStr string) error) error {
}
}
}
// fieldIndex returns the offset in line where the Nth field (0-based) begins, or -1
// if there aren't that many fields. Fields are separated by 1 or more spaces.
func fieldIndex(line []byte, n int) int {
skip := 0
for i := 0; i <= n; i++ {
// Skip spaces.
for skip < len(line) && line[skip] == ' ' {
skip++
}
if skip == len(line) {
return -1
}
if i == n {
break
}
// Skip non-space.
for skip < len(line) && line[skip] != ' ' {
skip++
}
}
return skip
}

43
portlist/portlist_linux_test.go
View File

@ -13,10 +13,34 @@ import (
"github.com/google/go-cmp/cmp"
)
func TestFieldIndex(t *testing.T) {
tests := []struct {
in string
field int
want int
}{
{"foo", 0, 0},
{" foo", 0, 2},
{"foo bar", 1, 5},
{" foo bar", 1, 6},
{" foo bar", 2, -1},
{" foo bar ", 2, -1},
{" foo bar x", 2, 10},
{" 1: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 34062 1 0000000000000000 100 0 0 10 0",
2, 19},
}
for _, tt := range tests {
if got := fieldIndex([]byte(tt.in), tt.field); got != tt.want {
t.Errorf("fieldIndex(%q, %v) = %v; want %v", tt.in, tt.field, got, tt.want)
}
}
}
func TestParsePorts(t *testing.T) {
tests := []struct {
name string
in string
file string
want []Port
}{
{
@ -26,6 +50,7 @@ func TestParsePorts(t *testing.T) {
},
{
name: "ipv4",
file: "tcp",
in: `header line
0: 0100007F:0277 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 22303 1 0000000000000000 100 0 0 10 0
1: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 34062 1 0000000000000000 100 0 0 10 0
@ -37,6 +62,7 @@ func TestParsePorts(t *testing.T) {
},
{
name: "ipv6",
file: "tcp6",
in: ` sl local_address remote_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode
0: 00000000000000000000000001000000:0277 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 35720 1 0000000000000000 100 0 0 10 0
1: 00000000000000000000000000000000:1F91 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 1000 0 142240557 1 0000000000000000 100 0 0 10 0
@ -50,17 +76,20 @@ func TestParsePorts(t *testing.T) {
},
}
for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
buf := bytes.NewBufferString(test.in)
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
buf := bytes.NewBufferString(tt.in)
r := bufio.NewReader(buf)
got, err := parsePorts(r, "tcp")
file := "tcp"
if tt.file != "" {
file = tt.file
}
got, err := parsePorts(r, file)
if err != nil {
t.Fatal(err)
}
if diff := cmp.Diff(got, test.want, cmp.AllowUnexported(Port{})); diff != "" {
if diff := cmp.Diff(got, tt.want, cmp.AllowUnexported(Port{})); diff != "" {
t.Errorf("unexpected parsed ports (-got+want):\n%s", diff)
}
})
@ -91,7 +120,7 @@ func BenchmarkParsePorts(b *testing.B) {
for i := 0; i < b.N; i++ {
r.Seek(0, io.SeekStart)
br.Reset(r)
got, err := parsePorts(br, "tcp")
got, err := parsePorts(br, "tcp6")
if err != nil {
b.Fatal(err)
}