internal/pkg: loadavg target in container environment

This exposes preferred loadavg target to the container initial process.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/exec.go

@@ -30,10 +30,16 @@ import (
 // AbsWork is the container pathname [TContext.GetWorkDir] is mounted on.
 var AbsWork = fhs.AbsRoot.Append("work/")
 
-// EnvJobs is the name of the environment variable holding a decimal
-// representation of the preferred job count. Its value must not affect cure
-// outcome.
-const EnvJobs = "CURE_JOBS"
+const (
+	// EnvJobs is the name of the environment variable holding a decimal
+	// representation of the preferred job count. Its value must not affect cure
+	// outcome.
+	EnvJobs = "CURE_JOBS"
+	// EnvLoad is the name of the environment variable holding a decimal
+	// representation of the preferred loadavg target. Its value must not affect
+	// cure outcome.
+	EnvLoad = "CURE_LOAD"
+)
 
 // ExecPath is a slice of [Artifact] and the [check.Absolute] pathname to make
 // it available at under in the container.
@@ -471,7 +477,7 @@ const SeccompPresets = std.PresetStrict &
 func (a *execArtifact) makeContainer(
 	ctx context.Context,
 	msg message.Msg,
-	flags, jobs int,
+	flags, jobs, load int,
 	hostNet bool,
 	temp, work *check.Absolute,
 	getArtifact GetArtifactFunc,
@@ -508,7 +514,10 @@ func (a *execArtifact) makeContainer(
 	z.Quiet = flags&CSuppressInit != 0
 	z.Uid, z.Gid = (1<<10)-1, (1<<10)-1
 	z.Dir, z.Path, z.Args = a.dir, a.path, a.args
-	z.Env = slices.Concat(a.env, []string{EnvJobs + "=" + strconv.Itoa(jobs)})
+	z.Env = slices.Concat(a.env, []string{
+		EnvJobs + "=" + strconv.Itoa(jobs),
+		EnvLoad + "=" + strconv.Itoa(load),
+	})
 	z.Grow(len(a.paths) + 4)
 
 	if a.arch != runtime.GOARCH {
@@ -651,6 +660,7 @@ func (c *Cache) EnterExec(
 		ctx, c.msg,
 		c.attr.Flags,
 		c.attr.Jobs,
+		c.attr.Load,
 		hostNet,
 		temp, work,
 		func(a Artifact) (*check.Absolute, unique.Handle[Checksum]) {
@@ -693,7 +703,7 @@ func (a *execArtifact) cure(f *FContext, hostNet bool) (err error) {
 	msg := f.GetMessage()
 	var z *container.Container
 	if z, err = a.makeContainer(
-		ctx, msg, f.cache.attr.Flags, f.GetJobs(), hostNet,
+		ctx, msg, f.cache.attr.Flags, f.GetJobs(), f.GetLoad(), hostNet,
 		f.GetTempDir(), f.GetWorkDir(),
 		f.GetArtifact,
 		f.cache.Ident,