feat: support adjusting child proc oom scores (#12655)

agent/agentproc/agentproctest/proc.go

@@ -2,6 +2,7 @@ package agentproctest
 
 import (
 	"fmt"
+	"strconv"
 	"testing"
 
 	"github.com/spf13/afero"
@@ -29,8 +30,9 @@ func GenerateProcess(t *testing.T, fs afero.Fs, muts ...func(*agentproc.Process)
 	cmdline := fmt.Sprintf("%s\x00%s\x00%s", arg1, arg2, arg3)
 
 	process := agentproc.Process{
-		CmdLine: cmdline,
-		PID:     int32(pid),
+		CmdLine:     cmdline,
+		PID:         int32(pid),
+		OOMScoreAdj: 0,
 	}
 
 	for _, mut := range muts {
@@ -45,5 +47,9 @@ func GenerateProcess(t *testing.T, fs afero.Fs, muts ...func(*agentproc.Process)
 	err = afero.WriteFile(fs, fmt.Sprintf("%s/cmdline", process.Dir), []byte(process.CmdLine), 0o444)
 	require.NoError(t, err)
 
+	score := strconv.Itoa(process.OOMScoreAdj)
+	err = afero.WriteFile(fs, fmt.Sprintf("%s/oom_score_adj", process.Dir), []byte(score), 0o444)
+	require.NoError(t, err)
+
 	return process
 }

agent/agentproc/proc_unix.go

@@ -5,6 +5,7 @@ package agentproc
 
 import (
 	"errors"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -50,10 +51,26 @@ func List(fs afero.Fs, syscaller Syscaller) ([]*Process, error) {
 			}
 			return nil, xerrors.Errorf("read cmdline: %w", err)
 		}
+
+		oomScore, err := afero.ReadFile(fs, filepath.Join(defaultProcDir, entry, "oom_score_adj"))
+		if err != nil {
+			if xerrors.Is(err, os.ErrPermission) {
+				continue
+			}
+
+			return nil, xerrors.Errorf("read oom_score_adj: %w", err)
+		}
+
+		oom, err := strconv.Atoi(strings.TrimSpace(string(oomScore)))
+		if err != nil {
+			return nil, xerrors.Errorf("convert oom score: %w", err)
+		}
+
 		processes = append(processes, &Process{
-			PID:     int32(pid),
-			CmdLine: string(cmdline),
-			Dir:     filepath.Join(defaultProcDir, entry),
+			PID:         int32(pid),
+			CmdLine:     string(cmdline),
+			Dir:         filepath.Join(defaultProcDir, entry),
+			OOMScoreAdj: oom,
 		})
 	}
 

agent/agentproc/syscaller.go

@@ -14,7 +14,8 @@ type Syscaller interface {
 const defaultProcDir = "/proc"
 
 type Process struct {
-	Dir     string
-	CmdLine string
-	PID     int32
+	Dir         string
+	CmdLine     string
+	PID         int32
+	OOMScoreAdj int
 }