Performance Tuning

OpenLiteSpeed is fast by default. These settings push it further — from baseline to production-optimized.

---

Performance Baseline — Before You Tune

# Establish baseline response time
curl -w "TTFB: %{time_starttransfer}s | Total: %{time_total}s\n" \
  -o /dev/null -s https://example.com/

# Check cache headers on a request
curl -I https://example.com/ | grep -iE "cache-control|etag|last-modified|x-cache"

# Check compression
curl -H "Accept-Encoding: gzip,br" -I https://example.com/ | grep -i "content-encoding"

# Check HTTP version
curl -I --http2 https://example.com/ 2>&1 | grep "HTTP/"

# Count requests per second (ab benchmark)
ab -n 1000 -c 10 https://example.com/ | grep "Requests per second"

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HTTP/2 and HTTP/3 / QUIC

Enable HTTP/2 (httpd_config.conf — HTTPS listener)

listener HTTPS {
  address                 *:443
  secure                  1
  ...
  # Enable HTTP/2 via ALPN
  alpn                    h2,http/1.1
}

Enable HTTP/3 / QUIC

listener HTTPS {
  address                 *:443
  secure                  1
  ...
  alpn                    h3,h2,http/1.1

  # QUIC uses UDP — ensure UDP 443 is open in firewall
  quic                    1
  quicShmDir              /dev/shm
}

# Check firewall allows UDP 443 for QUIC
sudo ufw allow 443/udp

# Verify HTTP/2 is negotiated
curl -I --http2 https://example.com/ | head -1
# Expected: HTTP/2 200

# Verify HTTP/3 (needs curl with h3 support)
curl -I --http3 https://example.com/ | head -1

---

Compression

vhconf.conf — compression settings

# Enable gzip (broad compatibility)
enableGzip                1

# Enable Brotli (better ratio, modern browsers)
enableBr                  1

# In httpd_config.conf — compression config block
compress  {
  # Minimum file size to compress
  compressMinSize         1024

  # Compress these MIME types
  compressibleTypes       text/html, text/css, text/javascript,
                          application/javascript, application/json,
                          application/xml, text/xml, image/svg+xml,
                          text/plain, application/xhtml+xml

  # Cache compressed output
  enableCache             1
}

Verify Compression

# Test gzip
curl -H "Accept-Encoding: gzip" -I https://example.com/ | grep "content-encoding"

# Test Brotli
curl -H "Accept-Encoding: br" -I https://example.com/ | grep "content-encoding"

# Check actual compressed size vs. uncompressed
curl -H "Accept-Encoding: gzip" -s https://example.com/ | wc -c
curl -s https://example.com/ | wc -c

---

LiteSpeed Cache (LSCache)

LSCache is OLS's built-in full-page cache. It works with the LSCache plugins for WordPress, Joomla, etc.

vhconf.conf — enable LSCache

# Enable the cache engine for this vhost
lsCache  {
  lscacheOn               1
  privateCacheTimeout     60
  publicCacheTimeout      86400
  dynamicCacheTimeout     0
}

# Check LSCache is responding
curl -I https://example.com/ | grep -i "x-litespeed-cache"
# Expected header: X-LiteSpeed-Cache: hit

# Purge LSCache for a domain (if LSCache plugin installed)
# Usually done via WP admin or curl with purge request
curl -X PURGE https://example.com/

Cache Headers from .htaccess

.htaccess — browser caching

<IfModule mod_expires.c>
  ExpiresActive On
  ExpiresByType image/jpg "access plus 1 year"
  ExpiresByType image/jpeg "access plus 1 year"
  ExpiresByType image/gif "access plus 1 year"
  ExpiresByType image/png "access plus 1 year"
  ExpiresByType image/webp "access plus 1 year"
  ExpiresByType image/svg+xml "access plus 1 year"
  ExpiresByType text/css "access plus 1 month"
  ExpiresByType text/javascript "access plus 1 month"
  ExpiresByType application/javascript "access plus 1 month"
  ExpiresByType application/x-font-woff "access plus 1 year"
  ExpiresByType font/woff2 "access plus 1 year"
  ExpiresDefault "access plus 1 week"
</IfModule>

# Cache-Control headers
<FilesMatch "\.(css|js|png|jpg|jpeg|gif|ico|webp|svg|woff|woff2)$">
  Header set Cache-Control "public, max-age=31536000, immutable"
</FilesMatch>

---

Connection Optimization (httpd_config.conf)

# ============================================================
# KEEP-ALIVE
# ============================================================
tuning  {
  maxKeepAliveReq         1000         # max requests per keep-alive
  keepAliveTimeout        5            # seconds to wait for next request
  sndBufSize              0            # 0 = OS default (auto)
  rcvBufSize              0            # 0 = OS default (auto)
  maxReqURLLen            32768        # max URL length
  maxReqHeaderSize        65536        # max header size
  maxReqBodySize          2G           # max upload body
  maxDynRespHeaderSize    32768
  maxDynRespSize          2G
}

# ============================================================
# CONNECTION LIMITS
# ============================================================
connLimit  {
  maxConnections          20000        # total server-wide
  maxSSLConnections       20000
  connHardLimit           10000        # per IP hard limit
  connSoftLimit           2000         # per IP soft limit (then throttle)
  gracePeriod             15           # seconds before hard limit kicks in
  banPeriod               300          # seconds to ban after hard limit
}

---

Static File Optimization

httpd_config.conf

# File descriptor cache (reduces open() syscalls)
fileCacheStat  {
  maxCacheEntries         4096
  maxCacheFileSize        1M
  maxSmallFileSize        4K
  smallFileDefaultAge     10
  largeFileDefaultAge     30
  fileStatRefreshInterval 60
}

vhconf.conf — static file context

# Serve uploads directly as static
context /wp-content/uploads {
  location                /var/www/example.com/public/wp-content/uploads
  allowBrowse             0
  accessControl  {
    allow                 *
  }
}

---

Reverse Proxy Caching (for Node.js / backend)

vhconf.conf — cache proxy responses

extprocessor node_app {
  type                    proxy
  address                 127.0.0.1:3000
  maxConns                100
  persistConn             1
  pcKeepAliveTimeout      60
}

context / {
  type                    proxy
  handler                 node_app
  addDefaultCharset       0
}

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Quick Wins Checklist

Optimization	Impact	How
Enable Brotli	Medium	enableBr 1 in vhconf
Enable HTTP/2	High	alpn h2,http/1.1 in listener
Enable OPcache	Very High	php.ini opcache.enable=1
Enable LSCache	Very High	lscacheOn 1 in vhconf
Set browser cache headers	High	.htaccess Expires rules
Tune PHP worker count	Medium	PHP_LSAPI_CHILDREN in extprocessor
Enable LSAPI_AVOID_FORK	Medium	Add to extprocessor env
Disable unused PHP extensions	Low	Remove from php.ini / conf.d
Enable file stat cache	Medium	fileCacheStat block

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Benchmarking

# ab (Apache Bench) — simple concurrency test
ab -n 5000 -c 50 https://example.com/

# wrk — modern HTTP benchmarking
wrk -t4 -c100 -d30s https://example.com/

# siege — stress test with multiple URLs
siege -c 25 -r 100 https://example.com/

# hey — simple Go-based load tester
hey -n 10000 -c 100 https://example.com/

# Check memory and CPU during load test
watch -n1 'ps aux | grep lshttpd | grep -v grep | head -5'
watch -n1 'free -m'