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cgroupv1: remove subsystemSet.Get() 

Instead of iterating over m.paths, iterate over subsystems and look up
the path for each. This is faster since a map lookup is faster than
iterating over the names in Get. A quick benchmark shows that the new
way is 2.5x faster than the old one.

Note though that this is not done to make things faster, as savings are
negligible, but to make things simpler by removing some code.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin 2020-06-03 09:11:20 -07:00
parent daf30cb7ca
commit 2a322e91ec
2 changed files with 8 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
libcontainer/cgroups/fs/fs.go
View File

@ -18,7 +18,7 @@ import (
)
var (
subsystems = subsystemSet{
subsystems = []subsystem{
&CpusetGroup{},
&DevicesGroup{},
&MemoryGroup{},
@ -38,17 +38,6 @@ var (
var errSubsystemDoesNotExist = errors.New("cgroup: subsystem does not exist")
type subsystemSet []subsystem
func (s subsystemSet) Get(name string) (subsystem, error) {
for _, ss := range s {
if ss.Name() == name {
return ss, nil
}
}
return nil, errSubsystemDoesNotExist
}
type subsystem interface {
// Name returns the name of the subsystem.
Name() string
@ -244,9 +233,9 @@ func (m *manager) GetStats() (*cgroups.Stats, error) {
m.mu.Lock()
defer m.mu.Unlock()
stats := cgroups.NewStats()
for name, path := range m.paths {
sys, err := subsystems.Get(name)
if err == errSubsystemDoesNotExist {
for _, sys := range subsystems {
path := m.paths[sys.Name()]
if path == "" {
continue
}
if err := sys.GetStats(path, stats); err != nil {

19
libcontainer/cgroups/systemd/v1.go
View File

@ -41,18 +41,7 @@ type subsystem interface {
var errSubsystemDoesNotExist = errors.New("cgroup: subsystem does not exist")
type subsystemSet []subsystem
func (s subsystemSet) Get(name string) (subsystem, error) {
for _, ss := range s {
if ss.Name() == name {
return ss, nil
}
}
return nil, errSubsystemDoesNotExist
}
var legacySubsystems = subsystemSet{
var legacySubsystems = []subsystem{
&fs.CpusetGroup{},
&fs.DevicesGroup{},
&fs.MemoryGroup{},
@ -355,9 +344,9 @@ func (m *legacyManager) GetStats() (*cgroups.Stats, error) {
m.mu.Lock()
defer m.mu.Unlock()
stats := cgroups.NewStats()
for name, path := range m.paths {
sys, err := legacySubsystems.Get(name)
if err == errSubsystemDoesNotExist || !cgroups.PathExists(path) {
for _, sys := range legacySubsystems {
path := m.paths[sys.Name()]
if path == "" {
continue
}
if err := sys.GetStats(path, stats); err != nil {