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Speed up VM create with work seeds

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Beat VM create wall time without changing VM semantics.

Generate a work-seed ext4 sidecar during image builds and rootfs rebuilds, then clone and resize that seed for each new VM instead of rebuilding /root from scratch. Plumb the new seed artifact through config, runtime metadata, store state, runtime-bundle defaults, doctor checks, and default-image reconciliation so older images still fall back cleanly.

Add a daemon TAP pool to keep idle bridge-attached devices warm, expose stage timing in lifecycle logs, add a create/SSH benchmark script plus Make target, and teach verify.sh that tap-pool-* devices are reusable capacity rather than cleanup leaks.

Validated with go test ./..., make build, ./verify.sh, and make bench-create ARGS="--runs 2".
This commit is contained in:
Thales Maciel 2026-03-18 21:22:12 -03:00
parent a14a80fd6b
commit c8d9a122f9
No known key found for this signature in database
GPG key ID: 33112E6833C34679
24 changed files with 695 additions and 44 deletions
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29
internal/daemon/capabilities.go
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@ -4,6 +4,7 @@ import (
"context"
"errors"
"net"
"os"
"strings"
"banger/internal/firecracker"
@ -150,10 +151,21 @@ type workDiskCapability struct{}
func (workDiskCapability) Name() string { return "work-disk" }
func (workDiskCapability) AddStartPreflight(_ context.Context, _ *Daemon, checks *system.Preflight, vm model.VMRecord, _ model.Image) {
func (workDiskCapability) AddStartPreflight(_ context.Context, _ *Daemon, checks *system.Preflight, vm model.VMRecord, image model.Image) {
if exists(vm.Runtime.WorkDiskPath) {
return
}
imageSeed := ""
if image.RootfsPath != "" {
imageSeed = image.WorkSeedPath
}
if exists(imageSeed) {
if info, err := os.Stat(imageSeed); err == nil && vm.Spec.WorkDiskSizeBytes > info.Size() {
checks.RequireCommand("e2fsck", toolHint("e2fsck"))
checks.RequireCommand("resize2fs", toolHint("resize2fs"))
}
return
}
for _, command := range []string{"mkfs.ext4", "mount", "umount", "cp"} {
checks.RequireCommand(command, toolHint(command))
}
@ -178,16 +190,23 @@ func (workDiskCapability) ContributeMachine(cfg *firecracker.MachineConfig, vm m
})
}
func (workDiskCapability) PrepareHost(ctx context.Context, d *Daemon, vm *model.VMRecord, _ model.Image) error {
return d.ensureWorkDisk(ctx, vm)
func (workDiskCapability) PrepareHost(ctx context.Context, d *Daemon, vm *model.VMRecord, image model.Image) error {
return d.ensureWorkDisk(ctx, vm, image)
}
func (workDiskCapability) AddDoctorChecks(_ context.Context, _ *Daemon, report *system.Report) {
func (workDiskCapability) AddDoctorChecks(_ context.Context, d *Daemon, report *system.Report) {
if strings.TrimSpace(d.config.DefaultWorkSeed) != "" && exists(d.config.DefaultWorkSeed) {
checks := system.NewPreflight()
checks.RequireFile(d.config.DefaultWorkSeed, "default work seed image", `rebuild the default runtime rootfs to regenerate the /root seed`)
report.AddPreflight("feature /root work disk", checks, "seeded /root work disk artifact available")
return
}
checks := system.NewPreflight()
for _, command := range []string{"mkfs.ext4", "mount", "umount", "cp"} {
checks.RequireCommand(command, toolHint(command))
}
report.AddPreflight("feature /root work disk", checks, "guest /root work disk tooling available")
report.AddPreflight("feature /root work disk", checks, "fallback /root work disk tooling available")
report.AddWarn("feature /root work disk", "default image has no work-seed artifact; new VM creates will be slower until the image is rebuilt")
}
type dnsCapability struct{}