Add benchmarking guide

Signed-off-by: DL6ER <dl6er@dl6er.de>

docs/guides/benchmark.md

@@ -0,0 +1,38 @@
+# Realistic benchmarking of your Pi-hole
+If you want to know how many queries - using the given hardware - your Pi-hole can handle to, e.g., estimate how many clients could be served, you could mass query domains from your long-term database.
+As the domains in the long-term database reflect **your particular** real-life usage, a benchmark on these domains should give you a good feeling for the performance of your Pi-hole.
+
+## 1. Extract the domains from the long-term database
+You can extract the domains using, e.g.,
+```
+sqlite3 /etc/pihole/pihole-FTL.db "SELECT domain FROM queries LIMIT 100000;" > domains.list
+```
+This will generate a list file with (up to) 100,000 domains. You can increase the upper limit of domains, however, I'd suggest to start from not too much data for getting realistic results in a reasonable period of time.
+
+They are extracted into the list file as they are recorded in the database. There will be lots of frequently queried domains (maybe `google.com` or similar) as well as some blocked ad domains. This list will serve you as an individualized testing bench for realistic DNS queries as typically seen in **your particular environment**.
+
+## 2. Optimize Pi-hole setting for benchmarking
+### 2.1 Disable logging
+We suggest disabling both logging as well as the long-term database during the benchmark run as both the log file and the database would otherwise unnecessarily grow (maybe be several hundreds of megabytes). Not only your statistics would be distorted by the artificial mass querying, the benchmark could also negatively be affected by the writing speed of your SD card.
+
+Logging can be disabled using `sudo pihole logging off`.
+
+The long-term database can disabled by setting
+```
+DBFILE=
+```
+in `/etc/pihole/pihole-FTL.conf` and running `sudo pihole restartdns` (see also [here](https://docs.pi-hole.net/ftldns/configfile/#dbfile)).
+
+### 2.2 Increase DNS cache size
+We also suggest to increase the DNS cache for benchmarking. The rather low value is fine for typical use cases. Domains will expire at some point and make room for new domains. As the benchmark will artificially increase the querying rate, there will be no time for the domains to expire naturally. This would dramatically hit the caching performance while you would never see such performance penalties in real use cases.
+
+Set `cache-size` to a rather high value (maybe 25,000 - by guess roughly one-eight to one-fourth number of the domains you extracted from the database in step 1) in `/etc/dnsmasq.d/01-pihole.conf` and run `sudo pihole restartdns` afterwards.
+
+## 3. Query domains from the list
+Use
+```
+time dig -f domains.list +noall +answer > /dev/null
+```
+for mass querying the domains from your list. This will show you how much time it takes to query the number of domains you extracted from the database.
+
+{!abbreviations.md!}

mkdocs.yml

@@ -84,6 +84,7 @@ nav:
   - 'Configuring NGINX for Pi-hole': guides/nginx-configuration.md
   - 'Configuring Caddy for Pi-hole': guides/caddy-configuration.md
   - 'Configuring Traefik for Pi-hole (not in Docker)': guides/traefik-configuration-nodocker.md
+  - 'Benchmarking': guides/benchmark.md
   - 'Pi-hole and OpenVPN Server':
     - 'Overview': guides/vpn/overview.md
     - 'Installation': guides/vpn/installation.md