Docker Performance Optimization

This chapter covers Docker container performance optimization strategies, including image optimization, runtime tuning, and resource management.

Image Size Optimization

Choose the Right Base Image

Base Image	Size	Use Case
scratch	0 MB	Statically compiled languages (Go)
alpine	~5 MB	Most scenarios
distroless	~20 MB	High security requirements
slim	~80-200 MB	Need more system tools
full	~800 MB+	Build stage

Reduce Layers

# ✅ Single RUN, fewer layers
RUN apt-get update && \
    apt-get install -y curl wget && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

Multi-Stage Builds

FROM node:20 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html

Build Speed Optimization

Leverage Build Cache

Place less-frequently-changing instructions first:

COPY package*.json ./
RUN npm ci
COPY . .

Use BuildKit

DOCKER_BUILDKIT=1 docker build -t myapp .

BuildKit benefits: parallel stage builds, smarter caching, better security.

Cache Dependency Downloads

RUN --mount=type=cache,target=/root/.cache/pip \
    pip install -r requirements.txt

Runtime Optimization

CPU

docker run --cpus 2 myapp              # Max 2 CPUs
docker run --cpu-shares 512 myapp       # CPU weight (relative)
docker run --cpuset-cpus "0,1" myapp    # Pin to specific cores

Memory

docker run -m 512m myapp               # Max 512MB
docker run -m 512m --memory-swap 1g myapp  # Memory + swap = 1GB

Storage

docker run --tmpfs /tmp:rw,size=100m myapp   # tmpfs for temp files
docker run -v mydata:/data myapp             # Named volumes (faster than bind mounts)

Network

docker run --network host myapp   # Host network (best performance, no isolation)

Resource Monitoring

docker stats
docker stats --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}"
docker system df
docker system df -v

Cleanup

docker system prune -a       # All unused resources
docker image prune -a        # Unused images
docker volume prune          # Unused volumes
docker builder prune         # Build cache

Optimization Checklist

Optimization	Impact	Priority
Use Alpine base images	Reduce image size	High
Multi-stage builds	Reduce image size	High
Leverage build cache	Speed up builds	High
.dockerignore	Speed up builds	Medium
Merge RUN instructions	Reduce layers	Medium
Resource limits	Prevent resource contention	High
Named volumes	Improve I/O performance	Medium
Enable BuildKit	Speed up builds	Medium

Chapter Summary

Docker performance optimization spans both image building and container runtime. Choose appropriate base images, leverage build cache, and configure resource limits to significantly improve Docker efficiency.

Further Reading

• Docker Resource Constraints
• BuildKit Documentation