libct/cg/fs2: set per-device io weight if available
Per-device weight is supported since kernel v5.4 (kernel commit
795fe54c2a8), so let's set those if supplied.
[v2: implement a more relaxed check in bfqDeviceWeightSupported]
@@ -4,6 +4,8 @@ package fs2
import (
"bufio"
+ "bytes"
+ "fmt"
"os"
"strconv"
"strings"
@@ -16,32 +18,64 @@ import (
func isIoSet(r *configs.Resources) bool {
return r.BlkioWeight != 0 ||
+ len(r.BlkioWeightDevice) > 0 ||
len(r.BlkioThrottleReadBpsDevice) > 0 ||
len(r.BlkioThrottleWriteBpsDevice) > 0 ||
len(r.BlkioThrottleReadIOPSDevice) > 0 ||
len(r.BlkioThrottleWriteIOPSDevice) > 0
}
+// bfqDeviceWeightSupported checks for per-device BFQ weight support (added
+// in kernel v5.4, commit 795fe54c2a8) by reading from "io.bfq.weight".
+func bfqDeviceWeightSupported(bfq *os.File) bool {
+ if bfq == nil {
+ return false
+ }
+ _, _ = bfq.Seek(0, 0)
+ buf := make([]byte, 32)
+ _, _ = bfq.Read(buf)
+ // If only a single number (default weight) if read back, we have older kernel.
+ _, err := strconv.ParseInt(string(bytes.TrimSpace(buf)), 10, 64)
+ return err != nil
+}
+
func setIo(dirPath string, r *configs.Resources) error {
if !isIoSet(r) {
return nil
}
+ // If BFQ IO scheduler is available, use it.
+ var bfq *os.File
+ if r.BlkioWeight != 0 || len(r.BlkioWeightDevice) > 0 {
+ var err error
+ bfq, err = cgroups.OpenFile(dirPath, "io.bfq.weight", os.O_RDWR)
+ if err == nil {
+ defer bfq.Close()
+ } else if !os.IsNotExist(err) {
+ return err
+ }
+ }
+
if r.BlkioWeight != 0 {
- filename := "io.bfq.weight"
- if err := cgroups.WriteFile(dirPath, filename,
- strconv.FormatUint(uint64(r.BlkioWeight), 10)); err != nil {
- // if io.bfq.weight does not exist, then bfq module is not loaded.
- // Fallback to use io.weight with a conversion scheme
- if !os.IsNotExist(err) {
+ if bfq != nil { // Use BFQ.
+ if _, err := bfq.WriteString(strconv.FormatUint(uint64(r.BlkioWeight), 10)); err != nil {
return err
}
+ } else {
+ // Fallback to io.weight with a conversion scheme.
v := cgroups.ConvertBlkIOToIOWeightValue(r.BlkioWeight)
if err := cgroups.WriteFile(dirPath, "io.weight", strconv.FormatUint(v, 10)); err != nil {
return err
}
}
}
+ if bfqDeviceWeightSupported(bfq) {
+ for _, wd := range r.BlkioWeightDevice {
+ if _, err := bfq.WriteString(wd.WeightString() + "\n"); err != nil {
+ return fmt.Errorf("setting device weight %q: %w", wd.WeightString(), err)
+ }
+ }
+ }
for _, td := range r.BlkioThrottleReadBpsDevice {
if err := cgroups.WriteFile(dirPath, "io.max", td.StringName("rbps")); err != nil {
return err
