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libcontainer/cgroups: GetAllPids: optimize 

1. Return earlier if there is an error.

2. Do not use filepath.Split on every entry, use info.Name() instead.

3. Make readProcsFile() accept file name as an argument, to avoid
   unnecessary file name and directory splitting and merging.

4. Skip on info.IsDir() -- this avoids an error when cgroup name is
   set to "cgroup.procs".

This is still not very good since filepath.Walk() performs an unnecessary
stat(2) on every entry, but better than before.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin 2020-03-20 12:21:28 -07:00
parent 12dc475dd6
commit 5542a2c77d
1 changed files with 8 additions and 9 deletions
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17
libcontainer/cgroups/utils.go
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@ -358,8 +358,8 @@ func getCgroupPathHelper(subsystem, cgroup string) (string, error) {
return filepath.Join(mnt, relCgroup), nil
}
func readProcsFile(dir string) ([]int, error) {
f, err := os.Open(filepath.Join(dir, CgroupProcesses))
func readProcsFile(file string) ([]int, error) {
f, err := os.Open(file)
if err != nil {
return nil, err
}
@ -514,8 +514,8 @@ func getHugePageSizeFromFilenames(fileNames []string) ([]string, error) {
}
// GetPids returns all pids, that were added to cgroup at path.
func GetPids(path string) ([]int, error) {
return readProcsFile(path)
func GetPids(dir string) ([]int, error) {
return readProcsFile(filepath.Join(dir, CgroupProcesses))
}
// GetAllPids returns all pids, that were added to cgroup at path and to all its
@ -524,14 +524,13 @@ func GetAllPids(path string) ([]int, error) {
var pids []int
// collect pids from all sub-cgroups
err := filepath.Walk(path, func(p string, info os.FileInfo, iErr error) error {
dir, file := filepath.Split(p)
if file != CgroupProcesses {
return nil
}
if iErr != nil {
return iErr
}
cPids, err := readProcsFile(dir)
if info.IsDir() || info.Name() != CgroupProcesses {
return nil
}
cPids, err := readProcsFile(p)
if err != nil {
return err
}