High CPU usage and bad browisng experience after upgrade to v6 from v5

[lan17]

Versions

• Pi-hole: v6.0.5
• AdminLTE:
• FTL: v6.0.4

Platform

• OS and version: Linux raspberrypi 6.6.20+rpt-rpi-v8 Update gravity-adv.sh pi-hole#1 SMP PREEMPT Debian 1:6.6.20-1+rpt1 (2024-03-07) aarch64 GNU/Linux

• Platform: Raspberry Pi

Expected behavior

Works fast, doesn't consume much CPU

Actual behavior / bug

Slow, consumes a lot of CPU, internet browsing is noticeably slower. ~15-20% CPU consumption vs <1% before.

It seems to be due to pihole-FTL

Steps to reproduce

Upgrade from v5 to v6. Must be some performance bugs.

Debug Token

• URL:

Screenshots

If applicable, add screenshots to help explain your problem.

Additional context

Add any other context about the problem here.

[yubiuser]

Please provide more information: when do you see high CPU usage? All the time? Only on HTTPS access to the web interface? Only during gravity run?
Please provide a debug token.

[FatherOfCurses]

I experienced the same issue when I ran an upgrade. I was running PiHole exclusively on a Pi3. The WebUI was horribly slow and DNS stopped resolving, I had to actually remove it from my network and point my router to Cloudflare.

[Peter1979pl]

Ich hatte überhaupt keine Probleme mit dem Update, trotz eines alte 3B+

admin edit - adding English:

I had no problems at all with the update, despite an old 3B+

[kevingufler]

I am running PiHole on a Proxmox environment.
The same problem here.
Was running perfectly before (v5) with one core and 500mb RAM.
Now (v6) it is struggling with 4 cores and 4GB RAM....

For me too it seems that pihole-FTL is the problem, as it has by far the most CPU time when checking on CLI.
When checking in Browser under System i get the following information: 143.7% (load: 5.75 19.78 12.48) on 4 cores running 894 processes (0.2% used by FTL)

The PiHole Dashboard sometimes shows CPU loads of 600% and DNS Requests get stuck.
Today PiHole did not respond for two minutes...

[FKdeveloper]

I have the same issue

• Raspberry pi model B rev 2 (yes one of the first ones)
• CPU BCM2835 @ 800MHz and 429MiB of RAM
• Raspbian lite (Raspbian GNU/Linux 11 (Bullseye) armv6l and kernel 6.1.21+

The previous V5 has had no issues at all for me. It was rock solid and now it's not working correctly anymore.
Some of the issues are as following:

• high cpu util
• slow web UI
• DNS resolver seems to be broken too.
  • Sometimes it works and most of the time it does not. Or run into the timeout limit.

It is dedicated to only run pihole.

Does anyone have a fix for this issue?

Edit:
Finally got to the system info tab in the web UI.

CPU: 168.5% (load: 1.95 1.68 1.72) on 1 core running 122 processes (78.2% used by FTL)

[2-10kur]

Same issue here, and also:

• Query log seems to stop at a certain point in time
• Refreshing the log does not have any effect
• Activating "Query on-disk data" in Advanced filtering" seems to trigger the CPU increase:
  CPU: 14.2% (load: 0.57 0.16 0.05) on 4 cores running 162 processes (56.2% used by FTL)
  Without the query log on-disk access:
  CPU: 0.0% (load: 0.00 0.05 0.07) on 4 cores running 161 processes (1.2% used by FTL)

• Raspbberry Pi 3 B Arm Cortex-A53, quad-core, 1 Gb RAM
• Linux 6.1.31-v8.1.el8.altarch Update gravity-adv.sh pi-hole#1 SMP PREEMPT Sat Jun 10 22:16:25 UTC 2023 aarch64

[dusancoko]

In my case, after the latest update of FTL, it used 100% of the CPU, the DNS server was blocked, and the GUI was also blocked.
After rebooting, it consumes all available RAM, and then my watchdog kills the process, which keeps repeating. Also, it taxes one of the cores to 100%.
Core [v6.0.4], FTL [v6.0.3] and Web UI [v6.0.1] are working fine, though, and there were no issues before the update yesterday to the new version. I restored the machine to its original state, hopefully this gets resolved soon.

[tspascoal]

Hi,

Facing the same issue (this machine is only used for pihole. Nothing else)

Core version is v6.0.5 (Latest: v6.0.5)
Web version is v6.0.2 (Latest: v6.0.2)
FTL version is v6.0.4 (Latest: v6.0.4)

Granted this is a pi zero, but version 5 handled this machine without any issues. Now I have high CPU usage (without the web UI open) and with some frequency DNS queries just fail

If this helps, this is htop output (and this is when the system is not actually that high. Load is only a little over 1, when it reaches 2 or 3 easily), it seems the database process takes quite a bit of CPU

This is the size of the long term database, don't know if it's related.

$  du -k /etc/pihole/pihole-FTL.db
722496  /etc/pihole/pihole-FTL.db

Should I do something to reduce this size? I don't really care that much about 365 of queries which I believe is the default value

If i open the web UI i get this

but htop doesn't really show CPU usage for the web workers

[2-10kur]

My personal workaround was to stop pihole-FTL, rename the database file and restart the pihole-FTL service. At least for the time being, the query log is seen correctly and the CPU usage decreased back to 1-2%

[tspascoal]

Deleting the database file did the trick.... CPU is now a lot more saner and no pihole failures so far

[NordFreak]

So I can confirm the following:

My Raspi configuration has not changed in the last few months. The last OS update was on February 26th - but the problems have only been occurring since the update to v6. None problems 4 years before. Today is the second time I've had this problem, which prompted me to go searching and I found this issue.

And renaming the DB file and restarting the service also helped me. (Thanks for the tip)

[voxdumnonia]

Just adding my voice to this issue. Like @FKdeveloper I've been running pihole on a rev 1.3 Model B for years. Renaming the database file works for a short time but after a couple of days of use (on a large home network with maybe two dozen clients), Load Average on htop is significantly above 1.0 across all three measures, DNS queries start to time out and the web interface becomes extraordinarily sluggish.
This is a setup that ran up to the V5.x releases with no performance issues whatsoever.

[voxdumnonia]

Just adding my voice to this issue. Like @FKdeveloper I've been running pihole on a rev 1.3 Model B for years. Renaming the database file works for a short time but after a couple of days of use (on a large home network with maybe two dozen clients), Load Average on htop is significantly above 1.0 across all three measures, DNS queries start to time out and the web interface becomes extraordinarily sluggish. This is a setup than ran up to the V5.x releases with no performance issues whatsoever.

Addendum: I don't think this should be happening - 10.02 1m load average with an uptime of under four hours! And what's it doing with all that swap space?!

[2-10kur]

Ah, forgot to mention, in my case I also did a swapoff -a - I do not see why it would need swap at all. Mine has been stable since I wrote the comment

[marcuccilli]

Thanks to the friends above for your help. Since upgrading to V6, I've frequently encountered issues where DNS fails to resolve any websites. I'm running Pi-hole on Proxmox VE. Following your advice, I deleted the database, and I haven’t experienced any domain resolution issues since. THX again!!!! Big THX!