Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

internal/runtime/cgroup: allow more tests to run on all OSes

Browse source 
Move non-Linux specific part out of _linux.go. The parsing code itself
doesn't depend anything Linux specific, even if it the format is Linux
specific.

This should benefit developers working on non-Linux OSes.

Change-Id: I1692978d583c3dd9a57ff269c97e8fca53a7a057
Reviewed-on: https://go-review.googlesource.com/c/go/+/723240
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Carrillo Rodriguez <carrillorodriguez672@gmail.com>
This commit is contained in:
胡玮文 2025-11-21 23:26:50 +08:00 • committed by Michael Pratt
parent 6e4a0d8e44
commit 1cc1337f0a
5 changed files with 428 additions and 425 deletions
Download patch file Download diff file Expand all files Collapse all files

418
src/internal/runtime/cgroup/cgroup.go Normal file
View file

@ -0,0 +1,418 @@
// Copyright 2025 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cgroup
import (
"internal/bytealg"
"internal/strconv"
)
var (
ErrNoCgroup error = stringError("not in a cgroup")
errMalformedFile error = stringError("malformed file")
)
const _PATH_MAX = 4096
const (
// Required amount of scratch space for CPULimit.
//
// TODO(prattmic): This is shockingly large (~70KiB) due to the (very
// unlikely) combination of extremely long paths consisting mostly
// escaped characters. The scratch buffer ends up in .bss in package
// runtime, so it doesn't contribute to binary size and generally won't
// be faulted in, but it would still be nice to shrink this. A more
// complex parser that did not need to keep entire lines in memory
// could get away with much less. Alternatively, we could do a one-off
// mmap allocation for this buffer, which is only mapped larger if we
// actually need the extra space.
ScratchSize = PathSize + ParseSize
// Required space to store a path of the cgroup in the filesystem.
PathSize = _PATH_MAX
// /proc/self/mountinfo path escape sequences are 4 characters long, so
// a path consisting entirely of escaped characters could be 4 times
// larger.
escapedPathMax = 4 * _PATH_MAX
// Required space to parse /proc/self/mountinfo and /proc/self/cgroup.
// See findCPUMount and findCPURelativePath.
ParseSize = 4 * escapedPathMax
)
// Version indicates the cgroup version.
type Version int
const (
VersionUnknown Version = iota
V1
V2
)
func parseV1Number(buf []byte) (int64, error) {
// Ignore trailing newline.
i := bytealg.IndexByte(buf, '\n')
if i < 0 {
return 0, errMalformedFile
}
buf = buf[:i]
val, err := strconv.ParseInt(string(buf), 10, 64)
if err != nil {
return 0, errMalformedFile
}
return val, nil
}
func parseV2Limit(buf []byte) (float64, bool, error) {
i := bytealg.IndexByte(buf, ' ')
if i < 0 {
return 0, false, errMalformedFile
}
quotaStr := buf[:i]
if bytealg.Compare(quotaStr, []byte("max")) == 0 {
// No limit.
return 0, false, nil
}
periodStr := buf[i+1:]
// Ignore trailing newline, if any.
i = bytealg.IndexByte(periodStr, '\n')
if i < 0 {
return 0, false, errMalformedFile
}
periodStr = periodStr[:i]
quota, err := strconv.ParseInt(string(quotaStr), 10, 64)
if err != nil {
return 0, false, errMalformedFile
}
period, err := strconv.ParseInt(string(periodStr), 10, 64)
if err != nil {
return 0, false, errMalformedFile
}
return float64(quota) / float64(period), true, nil
}
// Finds the path of the current process's CPU cgroup relative to the cgroup
// mount and writes it to out.
//
// Returns the number of bytes written and the cgroup version (1 or 2).
func parseCPURelativePath(fd int, read func(fd int, b []byte) (int, uintptr), out []byte, scratch []byte) (int, Version, error) {
// The format of each line is
//
// hierarchy-ID:controller-list:cgroup-path
//
// controller-list is comma-separated.
// See man 5 cgroup for more details.
//
// cgroup v2 has hierarchy-ID 0. If a v1 hierarchy contains "cpu", that
// is the CPU controller. Otherwise the v2 hierarchy (if any) is the
// CPU controller.
//
// hierarchy-ID and controller-list have relatively small maximum
// sizes, and the path can be up to _PATH_MAX, so we need a bit more
// than 1 _PATH_MAX of scratch space.
l := newLineReader(fd, scratch, read)
// Bytes written to out.
n := 0
for {
err := l.next()
if err == errIncompleteLine {
// Don't allow incomplete lines. While in theory the
// incomplete line may be for a controller we don't
// care about, in practice all lines should be of
// similar length, so we should just have a buffer big
// enough for any.
return 0, 0, err
} else if err == errEOF {
break
} else if err != nil {
return 0, 0, err
}
line := l.line()
// The format of each line is
//
// hierarchy-ID:controller-list:cgroup-path
//
// controller-list is comma-separated.
// See man 5 cgroup for more details.
i := bytealg.IndexByte(line, ':')
if i < 0 {
return 0, 0, errMalformedFile
}
hierarchy := line[:i]
line = line[i+1:]
i = bytealg.IndexByte(line, ':')
if i < 0 {
return 0, 0, errMalformedFile
}
controllers := line[:i]
line = line[i+1:]
path := line
if string(hierarchy) == "0" {
// v2 hierarchy.
n = copy(out, path)
// Keep searching, we might find a v1 hierarchy with a
// CPU controller, which takes precedence.
} else {
// v1 hierarchy
if containsCPU(controllers) {
// Found a v1 CPU controller. This must be the
// only one, so we're done.
return copy(out, path), V1, nil
}
}
}
if n == 0 {
// Found nothing.
return 0, 0, ErrNoCgroup
}
// Must be v2, v1 returns above.
return n, V2, nil
}
// Returns true if comma-separated list b contains "cpu".
func containsCPU(b []byte) bool {
for len(b) > 0 {
i := bytealg.IndexByte(b, ',')
if i < 0 {
// Neither cmd/compile nor gccgo allocates for these string conversions.
return string(b) == "cpu"
}
curr := b[:i]
rest := b[i+1:]
if string(curr) == "cpu" {
return true
}
b = rest
}
return false
}
// Returns the mount point for the cpu cgroup controller (v1 or v2) from
// /proc/self/mountinfo.
func parseCPUMount(fd int, read func(fd int, b []byte) (int, uintptr), out []byte, scratch []byte) (int, error) {
// The format of each line is:
//
// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
// (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
//
// (1) mount ID: unique identifier of the mount (may be reused after umount)
// (2) parent ID: ID of parent (or of self for the top of the mount tree)
// (3) major:minor: value of st_dev for files on filesystem
// (4) root: root of the mount within the filesystem
// (5) mount point: mount point relative to the process's root
// (6) mount options: per mount options
// (7) optional fields: zero or more fields of the form "tag[:value]"
// (8) separator: marks the end of the optional fields
// (9) filesystem type: name of filesystem of the form "type[.subtype]"
// (10) mount source: filesystem specific information or "none"
// (11) super options: per super block options
//
// See man 5 proc_pid_mountinfo for more details.
//
// Note that emitted paths will not contain space, tab, newline, or
// carriage return. Those are escaped. See Linux show_mountinfo ->
// show_path. We must unescape before returning.
//
// We return the mount point (5) if the filesystem type (9) is cgroup2,
// or cgroup with "cpu" in the super options (11).
//
// (4), (5), and (10) are up to _PATH_MAX. The remaining fields have a
// small fixed maximum size, so 4*_PATH_MAX is plenty of scratch space.
// Note that non-cgroup mounts may have arbitrarily long (11), but we
// can skip those when parsing.
l := newLineReader(fd, scratch, read)
// Bytes written to out.
n := 0
for {
//incomplete := false
err := l.next()
if err == errIncompleteLine {
// An incomplete line is fine as long as it doesn't
// impede parsing the fields we need. It shouldn't be
// possible for any mount to use more than 3*PATH_MAX
// before (9) because there are two paths and all other
// earlier fields have bounded options. Only (11) has
// unbounded options.
} else if err == errEOF {
break
} else if err != nil {
return 0, err
}
line := l.line()
// Skip first four fields.
for range 4 {
i := bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
line = line[i+1:]
}
// (5) mount point: mount point relative to the process's root
i := bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
mnt := line[:i]
line = line[i+1:]
// Skip ahead past optional fields, delimited by " - ".
for {
i = bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
if i+3 >= len(line) {
return 0, errMalformedFile
}
delim := line[i : i+3]
if string(delim) == " - " {
line = line[i+3:]
break
}
line = line[i+1:]
}
// (9) filesystem type: name of filesystem of the form "type[.subtype]"
i = bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
ftype := line[:i]
line = line[i+1:]
if string(ftype) != "cgroup" && string(ftype) != "cgroup2" {
continue
}
// As in findCPUPath, cgroup v1 with a CPU controller takes
// precendence over cgroup v2.
if string(ftype) == "cgroup2" {
// v2 hierarchy.
n, err = unescapePath(out, mnt)
if err != nil {
// Don't keep searching on error. The kernel
// should never produce broken escaping.
return n, err
}
// Keep searching, we might find a v1 hierarchy with a
// CPU controller, which takes precedence.
continue
}
// (10) mount source: filesystem specific information or "none"
i = bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
// Don't care about mount source.
line = line[i+1:]
// (11) super options: per super block options
superOpt := line
// v1 hierarchy
if containsCPU(superOpt) {
// Found a v1 CPU controller. This must be the
// only one, so we're done.
return unescapePath(out, mnt)
}
}
if n == 0 {
// Found nothing.
return 0, ErrNoCgroup
}
return n, nil
}
var errInvalidEscape error = stringError("invalid path escape sequence")
// unescapePath copies in to out, unescaping escape sequences generated by
// Linux's show_path.
//
// That is, '\', ' ', '\t', and '\n' are converted to octal escape sequences,
// like '\040' for space.
//
// out must be at least as large as in.
//
// Returns the number of bytes written to out.
//
// Also see escapePath in cgroup_linux_test.go.
func unescapePath(out []byte, in []byte) (int, error) {
// Not strictly necessary, but simplifies the implementation and will
// always hold in users.
if len(out) < len(in) {
throw("output too small")
}
var outi, ini int
for ini < len(in) {
c := in[ini]
if c != '\\' {
out[outi] = c
outi++
ini++
continue
}
// Start of escape sequence.
// Escape sequence is always 4 characters: one slash and three
// digits.
if ini+3 >= len(in) {
return outi, errInvalidEscape
}
var outc byte
for i := range 3 {
c := in[ini+1+i]
if c < '0' || c > '9' {
return outi, errInvalidEscape
}
outc *= 8
outc += c - '0'
}
out[outi] = outc
outi++
ini += 4
}
return outi, nil
}

410
src/internal/runtime/cgroup/cgroup_linux.go
View file

@ -5,44 +5,7 @@
package cgroup
import (
"internal/bytealg"
"internal/runtime/syscall/linux"
"internal/strconv"
)
var (
ErrNoCgroup error = stringError("not in a cgroup")
errMalformedFile error = stringError("malformed file")
)
const _PATH_MAX = 4096
const (
// Required amount of scratch space for CPULimit.
//
// TODO(prattmic): This is shockingly large (~70KiB) due to the (very
// unlikely) combination of extremely long paths consisting mostly
// escaped characters. The scratch buffer ends up in .bss in package
// runtime, so it doesn't contribute to binary size and generally won't
// be faulted in, but it would still be nice to shrink this. A more
// complex parser that did not need to keep entire lines in memory
// could get away with much less. Alternatively, we could do a one-off
// mmap allocation for this buffer, which is only mapped larger if we
// actually need the extra space.
ScratchSize = PathSize + ParseSize
// Required space to store a path of the cgroup in the filesystem.
PathSize = _PATH_MAX
// /proc/self/mountinfo path escape sequences are 4 characters long, so
// a path consisting entirely of escaped characters could be 4 times
// larger.
escapedPathMax = 4 * _PATH_MAX
// Required space to parse /proc/self/mountinfo and /proc/self/cgroup.
// See findCPUMount and findCPURelativePath.
ParseSize = 4 * escapedPathMax
)
// Include explicit NUL to be sure we include it in the slice.
@ -52,15 +15,6 @@ const (
v1PeriodFile = "/cpu.cfs_period_us\x00"
)
// Version indicates the cgroup version.
type Version int
const (
VersionUnknown Version = iota
V1
V2
)
// CPU owns the FDs required to read the CPU limit from a cgroup.
type CPU struct {
version Version
@ -212,22 +166,6 @@ func readV1Number(fd int) (int64, error) {
return parseV1Number(buf)
}
func parseV1Number(buf []byte) (int64, error) {
// Ignore trailing newline.
i := bytealg.IndexByte(buf, '\n')
if i < 0 {
return 0, errMalformedFile
}
buf = buf[:i]
val, err := strconv.ParseInt(string(buf), 10, 64)
if err != nil {
return 0, errMalformedFile
}
return val, nil
}
// Returns CPU throughput limit, or ok false if there is no limit.
func readV2Limit(fd int) (float64, bool, error) {
// The format of the file is "<quota> <period>\n" where quota and
@ -260,39 +198,6 @@ func readV2Limit(fd int) (float64, bool, error) {
return parseV2Limit(buf)
}
func parseV2Limit(buf []byte) (float64, bool, error) {
i := bytealg.IndexByte(buf, ' ')
if i < 0 {
return 0, false, errMalformedFile
}
quotaStr := buf[:i]
if bytealg.Compare(quotaStr, []byte("max")) == 0 {
// No limit.
return 0, false, nil
}
periodStr := buf[i+1:]
// Ignore trailing newline, if any.
i = bytealg.IndexByte(periodStr, '\n')
if i < 0 {
return 0, false, errMalformedFile
}
periodStr = periodStr[:i]
quota, err := strconv.ParseInt(string(quotaStr), 10, 64)
if err != nil {
return 0, false, errMalformedFile
}
period, err := strconv.ParseInt(string(periodStr), 10, 64)
if err != nil {
return 0, false, errMalformedFile
}
return float64(quota) / float64(period), true, nil
}
// FindCPU finds the path to the CPU cgroup that this process is a member of
// and places it in out. scratch is a scratch buffer for internal use.
//
@ -364,118 +269,6 @@ func FindCPURelativePath(out []byte, scratch []byte) (int, Version, error) {
return n, version, nil
}
// Finds the path of the current process's CPU cgroup relative to the cgroup
// mount and writes it to out.
//
// Returns the number of bytes written and the cgroup version (1 or 2).
func parseCPURelativePath(fd int, read func(fd int, b []byte) (int, uintptr), out []byte, scratch []byte) (int, Version, error) {
// The format of each line is
//
// hierarchy-ID:controller-list:cgroup-path
//
// controller-list is comma-separated.
// See man 5 cgroup for more details.
//
// cgroup v2 has hierarchy-ID 0. If a v1 hierarchy contains "cpu", that
// is the CPU controller. Otherwise the v2 hierarchy (if any) is the
// CPU controller.
//
// hierarchy-ID and controller-list have relatively small maximum
// sizes, and the path can be up to _PATH_MAX, so we need a bit more
// than 1 _PATH_MAX of scratch space.
l := newLineReader(fd, scratch, read)
// Bytes written to out.
n := 0
for {
err := l.next()
if err == errIncompleteLine {
// Don't allow incomplete lines. While in theory the
// incomplete line may be for a controller we don't
// care about, in practice all lines should be of
// similar length, so we should just have a buffer big
// enough for any.
return 0, 0, err
} else if err == errEOF {
break
} else if err != nil {
return 0, 0, err
}
line := l.line()
// The format of each line is
//
// hierarchy-ID:controller-list:cgroup-path
//
// controller-list is comma-separated.
// See man 5 cgroup for more details.
i := bytealg.IndexByte(line, ':')
if i < 0 {
return 0, 0, errMalformedFile
}
hierarchy := line[:i]
line = line[i+1:]
i = bytealg.IndexByte(line, ':')
if i < 0 {
return 0, 0, errMalformedFile
}
controllers := line[:i]
line = line[i+1:]
path := line
if string(hierarchy) == "0" {
// v2 hierarchy.
n = copy(out, path)
// Keep searching, we might find a v1 hierarchy with a
// CPU controller, which takes precedence.
} else {
// v1 hierarchy
if containsCPU(controllers) {
// Found a v1 CPU controller. This must be the
// only one, so we're done.
return copy(out, path), V1, nil
}
}
}
if n == 0 {
// Found nothing.
return 0, 0, ErrNoCgroup
}
// Must be v2, v1 returns above.
return n, V2, nil
}
// Returns true if comma-separated list b contains "cpu".
func containsCPU(b []byte) bool {
for len(b) > 0 {
i := bytealg.IndexByte(b, ',')
if i < 0 {
// Neither cmd/compile nor gccgo allocates for these string conversions.
return string(b) == "cpu"
}
curr := b[:i]
rest := b[i+1:]
if string(curr) == "cpu" {
return true
}
b = rest
}
return false
}
// FindCPUMountPoint finds the root of the CPU cgroup mount places it in out.
// scratch is a scratch buffer for internal use.
//
@ -505,206 +298,3 @@ func FindCPUMountPoint(out []byte, scratch []byte) (int, error) {
return n, nil
}
// Returns the mount point for the cpu cgroup controller (v1 or v2) from
// /proc/self/mountinfo.
func parseCPUMount(fd int, read func(fd int, b []byte) (int, uintptr), out []byte, scratch []byte) (int, error) {
// The format of each line is:
//
// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
// (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
//
// (1) mount ID: unique identifier of the mount (may be reused after umount)
// (2) parent ID: ID of parent (or of self for the top of the mount tree)
// (3) major:minor: value of st_dev for files on filesystem
// (4) root: root of the mount within the filesystem
// (5) mount point: mount point relative to the process's root
// (6) mount options: per mount options
// (7) optional fields: zero or more fields of the form "tag[:value]"
// (8) separator: marks the end of the optional fields
// (9) filesystem type: name of filesystem of the form "type[.subtype]"
// (10) mount source: filesystem specific information or "none"
// (11) super options: per super block options
//
// See man 5 proc_pid_mountinfo for more details.
//
// Note that emitted paths will not contain space, tab, newline, or
// carriage return. Those are escaped. See Linux show_mountinfo ->
// show_path. We must unescape before returning.
//
// We return the mount point (5) if the filesystem type (9) is cgroup2,
// or cgroup with "cpu" in the super options (11).
//
// (4), (5), and (10) are up to _PATH_MAX. The remaining fields have a
// small fixed maximum size, so 4*_PATH_MAX is plenty of scratch space.
// Note that non-cgroup mounts may have arbitrarily long (11), but we
// can skip those when parsing.
l := newLineReader(fd, scratch, read)
// Bytes written to out.
n := 0
for {
//incomplete := false
err := l.next()
if err == errIncompleteLine {
// An incomplete line is fine as long as it doesn't
// impede parsing the fields we need. It shouldn't be
// possible for any mount to use more than 3*PATH_MAX
// before (9) because there are two paths and all other
// earlier fields have bounded options. Only (11) has
// unbounded options.
} else if err == errEOF {
break
} else if err != nil {
return 0, err
}
line := l.line()
// Skip first four fields.
for range 4 {
i := bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
line = line[i+1:]
}
// (5) mount point: mount point relative to the process's root
i := bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
mnt := line[:i]
line = line[i+1:]
// Skip ahead past optional fields, delimited by " - ".
for {
i = bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
if i+3 >= len(line) {
return 0, errMalformedFile
}
delim := line[i : i+3]
if string(delim) == " - " {
line = line[i+3:]
break
}
line = line[i+1:]
}
// (9) filesystem type: name of filesystem of the form "type[.subtype]"
i = bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
ftype := line[:i]
line = line[i+1:]
if string(ftype) != "cgroup" && string(ftype) != "cgroup2" {
continue
}
// As in findCPUPath, cgroup v1 with a CPU controller takes
// precendence over cgroup v2.
if string(ftype) == "cgroup2" {
// v2 hierarchy.
n, err = unescapePath(out, mnt)
if err != nil {
// Don't keep searching on error. The kernel
// should never produce broken escaping.
return n, err
}
// Keep searching, we might find a v1 hierarchy with a
// CPU controller, which takes precedence.
continue
}
// (10) mount source: filesystem specific information or "none"
i = bytealg.IndexByte(line, ' ')
if i < 0 {
return 0, errMalformedFile
}
// Don't care about mount source.
line = line[i+1:]
// (11) super options: per super block options
superOpt := line
// v1 hierarchy
if containsCPU(superOpt) {
// Found a v1 CPU controller. This must be the
// only one, so we're done.
return unescapePath(out, mnt)
}
}
if n == 0 {
// Found nothing.
return 0, ErrNoCgroup
}
return n, nil
}
var errInvalidEscape error = stringError("invalid path escape sequence")
// unescapePath copies in to out, unescaping escape sequences generated by
// Linux's show_path.
//
// That is, '\', ' ', '\t', and '\n' are converted to octal escape sequences,
// like '\040' for space.
//
// out must be at least as large as in.
//
// Returns the number of bytes written to out.
//
// Also see escapePath in cgroup_linux_test.go.
func unescapePath(out []byte, in []byte) (int, error) {
// Not strictly necessary, but simplifies the implementation and will
// always hold in users.
if len(out) < len(in) {
throw("output too small")
}
var outi, ini int
for ini < len(in) {
c := in[ini]
if c != '\\' {
out[outi] = c
outi++
ini++
continue
}
// Start of escape sequence.
// Escape sequence is always 4 characters: one slash and three
// digits.
if ini+3 >= len(in) {
return outi, errInvalidEscape
}
var outc byte
for i := range 3 {
c := in[ini+1+i]
if c < '0' || c > '9' {
return outi, errInvalidEscape
}
outc *= 8
outc += c - '0'
}
out[outi] = outc
outi++
ini += 4
}
return outi, nil
}

0
src/internal/runtime/cgroup/cgroup_linux_test.go → src/internal/runtime/cgroup/cgroup_test.go
View file

15
src/internal/runtime/cgroup/export_linux_test.go
View file

@ -1,15 +0,0 @@
// Copyright 2025 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cgroup
var ContainsCPU = containsCPU
var ParseV1Number = parseV1Number
var ParseV2Limit = parseV2Limit
var ParseCPURelativePath = parseCPURelativePath
var ParseCPUMount = parseCPUMount
var UnescapePath = unescapePath

10
src/internal/runtime/cgroup/export_test.go
View file

@ -22,3 +22,13 @@ var (
ErrEOF = errEOF
ErrIncompleteLine = errIncompleteLine
)
var ContainsCPU = containsCPU
var ParseV1Number = parseV1Number
var ParseV2Limit = parseV2Limit
var ParseCPURelativePath = parseCPURelativePath
var ParseCPUMount = parseCPUMount
var UnescapePath = unescapePath