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// +build linux
package intelrdt
import (
"bufio"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"github.com/opencontainers/runc/libcontainer/configs"
)
/*
* About Intel RDT/CAT feature:
* Intel platforms with new Xeon CPU support Resource Director Technology (RDT).
* Intel Cache Allocation Technology (CAT) is a sub-feature of RDT. Currently L3
* Cache is the only resource that is supported in RDT.
*
* This feature provides a way for the software to restrict cache allocation to a
* defined 'subset' of L3 cache which may be overlapping with other 'subsets'.
* The different subsets are identified by class of service (CLOS) and each CLOS
* has a capacity bitmask (CBM).
*
* For more information about Intel RDT/CAT can be found in the section 17.17
* of Intel Software Developer Manual.
*
* About Intel RDT/CAT kernel interface:
* In Linux 4.10 kernel or newer, the interface is defined and exposed via
* "resource control" filesystem, which is a "cgroup-like" interface.
*
* Comparing with cgroups, it has similar process management lifecycle and
* interfaces in a container. But unlike cgroups' hierarchy, it has single level
* filesystem layout.
*
* Intel RDT "resource control" filesystem hierarchy:
* mount -t resctrl resctrl /sys/fs/resctrl
* tree /sys/fs/resctrl
* /sys/fs/resctrl/
* |-- info
* | |-- L3
* | |-- cbm_mask
* | |-- min_cbm_bits
* | |-- num_closids
* |-- cpus
* |-- schemata
* |-- tasks
* |-- <container_id>
* |-- cpus
* |-- schemata
* |-- tasks
*
* For runc, we can make use of `tasks` and `schemata` configuration for L3 cache
* resource constraints.
*
* The file `tasks` has a list of tasks that belongs to this group (e.g.,
* <container_id>" group). Tasks can be added to a group by writing the task ID
* to the "tasks" file (which will automatically remove them from the previous
* group to which they belonged). New tasks created by fork(2) and clone(2) are
* added to the same group as their parent. If a pid is not in any sub group, it is
* in root group.
*
* The file `schemata` has allocation bitmasks/values for L3 cache on each socket,
* which contains L3 cache id and capacity bitmask (CBM).
* Format: "L3:<cache_id0>=<cbm0>;<cache_id1>=<cbm1>;..."
* For example, on a two-socket machine, L3's schema line could be `L3:0=ff;1=c0`
* which means L3 cache id 0's CBM is 0xff, and L3 cache id 1's CBM is 0xc0.
*
* The valid L3 cache CBM is a *contiguous bits set* and number of bits that can
* be set is less than the max bit. The max bits in the CBM is varied among
* supported Intel Xeon platforms. In Intel RDT "resource control" filesystem
* layout, the CBM in a group should be a subset of the CBM in root. Kernel will
* check if it is valid when writing. e.g., 0xfffff in root indicates the max bits
* of CBM is 20 bits, which mapping to entire L3 cache capacity. Some valid CBM
* values to set in a group: 0xf, 0xf0, 0x3ff, 0x1f00 and etc.
*
* For more information about Intel RDT/CAT kernel interface:
* https://www.kernel.org/doc/Documentation/x86/intel_rdt_ui.txt
*
* An example for runc:
* Consider a two-socket machine with two L3 caches where the default CBM is
* 0xfffff and the max CBM length is 20 bits. With this configuration, tasks
* inside the container only have access to the "upper" 80% of L3 cache id 0 and
* the "lower" 50% L3 cache id 1:
*
* "linux": {
* "intelRdt": {
* "l3CacheSchema": "L3:0=ffff0;1=3ff"
* }
* }
*/
type Manager interface {
// Applies Intel RDT configuration to the process with the specified pid
Apply(pid int) error
// Returns statistics for Intel RDT
GetStats() (*Stats, error)
// Destroys the Intel RDT 'container_id' group
Destroy() error
// Returns Intel RDT path to save in a state file and to be able to
// restore the object later
GetPath() string
// Set Intel RDT "resource control" filesystem as configured.
Set(container *configs.Config) error
}
// This implements interface Manager
type IntelRdtManager struct {
mu sync.Mutex
Config *configs.Config
Id string
Path string
}
const (
IntelRdtTasks = "tasks"
)
var (
// The absolute root path of the Intel RDT "resource control" filesystem
intelRdtRoot string
intelRdtRootLock sync.Mutex
// The flag to indicate if Intel RDT is supported
isEnabled bool
)
type intelRdtData struct {
root string
config *configs.Config
pid int
}
// Check if Intel RDT is enabled in init()
func init() {
// 1. Check if hardware and kernel support Intel RDT/CAT feature
// "cat_l3" flag is set if supported
isFlagSet, err := parseCpuInfoFile("/proc/cpuinfo")
if !isFlagSet || err != nil {
isEnabled = false
return
}
// 2. Check if Intel RDT "resource control" filesystem is mounted
// The user guarantees to mount the filesystem
isEnabled = isIntelRdtMounted()
}
// Return the mount point path of Intel RDT "resource control" filesysem
func findIntelRdtMountpointDir() (string, error) {
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return "", err
}
defer f.Close()
s := bufio.NewScanner(f)
for s.Scan() {
text := s.Text()
fields := strings.Split(text, " ")
// Safe as mountinfo encodes mountpoints with spaces as \040.
index := strings.Index(text, " - ")
postSeparatorFields := strings.Fields(text[index+3:])
numPostFields := len(postSeparatorFields)
// This is an error as we can't detect if the mount is for "Intel RDT"
if numPostFields == 0 {
return "", fmt.Errorf("Found no fields post '-' in %q", text)
}
if postSeparatorFields[0] == "resctrl" {
// Check that the mount is properly formatted.
if numPostFields < 3 {
return "", fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
}
return fields[4], nil
}
}
if err := s.Err(); err != nil {
return "", err
}
return "", NewNotFoundError("Intel RDT")
}
// Gets the root path of Intel RDT "resource control" filesystem
func getIntelRdtRoot() (string, error) {
intelRdtRootLock.Lock()
defer intelRdtRootLock.Unlock()
if intelRdtRoot != "" {
return intelRdtRoot, nil
}
root, err := findIntelRdtMountpointDir()
if err != nil {
return "", err
}
if _, err := os.Stat(root); err != nil {
return "", err
}
intelRdtRoot = root
return intelRdtRoot, nil
}
func isIntelRdtMounted() bool {
_, err := getIntelRdtRoot()
if err != nil {
return false
}
return true
}
func parseCpuInfoFile(path string) (bool, error) {
f, err := os.Open(path)
if err != nil {
return false, err
}
defer f.Close()
s := bufio.NewScanner(f)
for s.Scan() {
if err := s.Err(); err != nil {
return false, err
}
text := s.Text()
flags := strings.Split(text, " ")
// "cat_l3" flag is set if Intel RDT/CAT is supported
for _, flag := range flags {
if flag == "cat_l3" {
return true, nil
}
}
}
return false, nil
}
func parseUint(s string, base, bitSize int) (uint64, error) {
value, err := strconv.ParseUint(s, base, bitSize)
if err != nil {
intValue, intErr := strconv.ParseInt(s, base, bitSize)
// 1. Handle negative values greater than MinInt64 (and)
// 2. Handle negative values lesser than MinInt64
if intErr == nil && intValue < 0 {
return 0, nil
} else if intErr != nil && intErr.(*strconv.NumError).Err == strconv.ErrRange && intValue < 0 {
return 0, nil
}
return value, err
}
return value, nil
}
// Gets a single uint64 value from the specified file.
func getIntelRdtParamUint(path, file string) (uint64, error) {
fileName := filepath.Join(path, file)
contents, err := ioutil.ReadFile(fileName)
if err != nil {
return 0, err
}
res, err := parseUint(strings.TrimSpace(string(contents)), 10, 64)
if err != nil {
return res, fmt.Errorf("unable to parse %q as a uint from file %q", string(contents), fileName)
}
return res, nil
}
// Gets a string value from the specified file
func getIntelRdtParamString(path, file string) (string, error) {
contents, err := ioutil.ReadFile(filepath.Join(path, file))
if err != nil {
return "", err
}
return strings.TrimSpace(string(contents)), nil
}
func readTasksFile(dir string) ([]int, error) {
f, err := os.Open(filepath.Join(dir, IntelRdtTasks))
if err != nil {
return nil, err
}
defer f.Close()
var (
s = bufio.NewScanner(f)
out = []int{}
)
for s.Scan() {
if t := s.Text(); t != "" {
pid, err := strconv.Atoi(t)
if err != nil {
return nil, err
}
out = append(out, pid)
}
}
return out, nil
}
func writeFile(dir, file, data string) error {
if dir == "" {
return fmt.Errorf("no such directory for %s", file)
}
if err := ioutil.WriteFile(filepath.Join(dir, file), []byte(data+"\n"), 0700); err != nil {
return fmt.Errorf("failed to write %v to %v: %v", data, file, err)
}
return nil
}
func getIntelRdtData(c *configs.Config, pid int) (*intelRdtData, error) {
rootPath, err := getIntelRdtRoot()
if err != nil {
return nil, err
}
return &intelRdtData{
root: rootPath,
config: c,
pid: pid,
}, nil
}
// Get the read-only L3 cache information
func getL3CacheInfo() (*L3CacheInfo, error) {
l3CacheInfo := &L3CacheInfo{}
rootPath, err := getIntelRdtRoot()
if err != nil {
return l3CacheInfo, err
}
path := filepath.Join(rootPath, "info", "L3")
cbmMask, err := getIntelRdtParamString(path, "cbm_mask")
if err != nil {
return l3CacheInfo, err
}
minCbmBits, err := getIntelRdtParamUint(path, "min_cbm_bits")
if err != nil {
return l3CacheInfo, err
}
numClosids, err := getIntelRdtParamUint(path, "num_closids")
if err != nil {
return l3CacheInfo, err
}
l3CacheInfo.CbmMask = cbmMask
l3CacheInfo.MinCbmBits = minCbmBits
l3CacheInfo.NumClosids = numClosids
return l3CacheInfo, nil
}
// WriteIntelRdtTasks writes the specified pid into the "tasks" file
func WriteIntelRdtTasks(dir string, pid int) error {
if dir == "" {
return fmt.Errorf("no such directory for %s", IntelRdtTasks)
}
// Dont attach any pid if -1 is specified as a pid
if pid != -1 {
if err := ioutil.WriteFile(filepath.Join(dir, IntelRdtTasks), []byte(strconv.Itoa(pid)), 0700); err != nil {
return fmt.Errorf("failed to write %v to %v: %v", pid, IntelRdtTasks, err)
}
}
return nil
}
// Check if Intel RDT is enabled
func IsEnabled() bool {
return isEnabled
}
// Get the 'container_id' path in Intel RDT "resource control" filesystem
func GetIntelRdtPath(id string) (string, error) {
rootPath, err := getIntelRdtRoot()
if err != nil {
return "", err
}
path := filepath.Join(rootPath, id)
return path, nil
}
// Applies Intel RDT configuration to the process with the specified pid
func (m *IntelRdtManager) Apply(pid int) (err error) {
// If intelRdt is not specified in config, we do nothing
if m.Config.IntelRdt == nil {
return nil
}
d, err := getIntelRdtData(m.Config, pid)
if err != nil && !IsNotFound(err) {
return err
}
m.mu.Lock()
defer m.mu.Unlock()
path, err := d.join(m.Id)
if err != nil {
return err
}
m.Path = path
return nil
}
// Destroys the Intel RDT 'container_id' group
func (m *IntelRdtManager) Destroy() error {
m.mu.Lock()
defer m.mu.Unlock()
if err := os.RemoveAll(m.Path); err != nil {
return err
}
m.Path = ""
return nil
}
// Returns Intel RDT path to save in a state file and to be able to
// restore the object later
func (m *IntelRdtManager) GetPath() string {
if m.Path == "" {
m.Path, _ = GetIntelRdtPath(m.Id)
}
return m.Path
}
// Returns statistics for Intel RDT
func (m *IntelRdtManager) GetStats() (*Stats, error) {
// If intelRdt is not specified in config
if m.Config.IntelRdt == nil {
return nil, nil
}
m.mu.Lock()
defer m.mu.Unlock()
stats := NewStats()
// The read-only L3 cache information
l3CacheInfo, err := getL3CacheInfo()
if err != nil {
return nil, err
}
stats.L3CacheInfo = l3CacheInfo
// The read-only L3 cache schema in root
rootPath, err := getIntelRdtRoot()
if err != nil {
return nil, err
}
tmpRootStrings, err := getIntelRdtParamString(rootPath, "schemata")
if err != nil {
return nil, err
}
// L3 cache schema is in the first line
schemaRootStrings := strings.Split(tmpRootStrings, "\n")
stats.L3CacheSchemaRoot = schemaRootStrings[0]
// The L3 cache schema in 'container_id' group
tmpStrings, err := getIntelRdtParamString(m.GetPath(), "schemata")
if err != nil {
return nil, err
}
// L3 cache schema is in the first line
schemaStrings := strings.Split(tmpStrings, "\n")
stats.L3CacheSchema = schemaStrings[0]
return stats, nil
}
// Set Intel RDT "resource control" filesystem as configured.
func (m *IntelRdtManager) Set(container *configs.Config) error {
path := m.GetPath()
// About L3 cache schema file:
// The schema has allocation masks/values for L3 cache on each socket,
// which contains L3 cache id and capacity bitmask (CBM).
// Format: "L3:<cache_id0>=<cbm0>;<cache_id1>=<cbm1>;..."
// For example, on a two-socket machine, L3's schema line could be:
// L3:0=ff;1=c0
// Which means L3 cache id 0's CBM is 0xff, and L3 cache id 1's CBM is 0xc0.
//
// About L3 cache CBM validity:
// The valid L3 cache CBM is a *contiguous bits set* and number of
// bits that can be set is less than the max bit. The max bits in the
// CBM is varied among supported Intel Xeon platforms. In Intel RDT
// "resource control" filesystem layout, the CBM in a group should
// be a subset of the CBM in root. Kernel will check if it is valid
// when writing.
// e.g., 0xfffff in root indicates the max bits of CBM is 20 bits,
// which mapping to entire L3 cache capacity. Some valid CBM values
// to set in a group: 0xf, 0xf0, 0x3ff, 0x1f00 and etc.
if container.IntelRdt != nil {
l3CacheSchema := container.IntelRdt.L3CacheSchema
if l3CacheSchema != "" {
if err := writeFile(path, "schemata", l3CacheSchema); err != nil {
return err
}
}
}
return nil
}
func (raw *intelRdtData) join(id string) (string, error) {
path := filepath.Join(raw.root, id)
if err := os.MkdirAll(path, 0755); err != nil {
return "", err
}
if err := WriteIntelRdtTasks(path, raw.pid); err != nil {
return "", err
}
return path, nil
}
type NotFoundError struct {
ResourceControl string
}
func (e *NotFoundError) Error() string {
return fmt.Sprintf("mountpoint for %s not found", e.ResourceControl)
}
func NewNotFoundError(res string) error {
return &NotFoundError{
ResourceControl: res,
}
}
func IsNotFound(err error) bool {
if err == nil {
return false
}
_, ok := err.(*NotFoundError)
return ok
}