100% CPU usage while downloading at max speed after upgrade to 24.10.0

Installing and Using OpenWrt
1

I upgraded my router TP-Link Archer C7 AC1750 from Openwrt 23.05.5 to 24.10.0.
The first issue I had was that the internal filesystem storage size was almost full, so I could not re-install dnscrypt-proxy2 that I had previously installed, therefore I dediced to enable Extroot to use external USB to expand root filesystem.

Now I have another issue: when downloading big files at maximum speed and so using all my download bandwidth I noticed a 100% CPU usage (with all the consequences of that, e.g. Wifi 5Ghz starts disconneting, router is generally unresponsive, can't access the router in SSH etc...).

While any file is downloading at maximum speed, I noticed from top command that the processes that are taking more CPU are mainly the following ones:

[ksoftirqd/0]
/usr/sbin/hostapd -s -g /var/run/hostapd/global
kworker/0:0-eve]
kworker/0:2H-kb]

I don't understand what could be the issue. Could it be the I/O communication with my USB device (I tested and it's fast, though), or some bug with hostapd, or what?
The more the downloading speed is increasing, the more CPU is used!
Is there anything I can do to mitigate that somehow?
I want to underline that I did not have this issue while on 23.05.5.

There are no errors in logread.
Other packages I'm using that could be relevant for the issue:

  • dnscrypt-proxy2 v2.1.5-r1
  • adblock v4.2.7-r2
    But I noticed that both do not contribute to the issue, since I temporary disabled both and I still have the issue.

Thanks

2

Cam you repeat problem taking usb out of picture completely? Neither of 2 packages are huge to warrant using extroot.

3

I know, but the storage size of my router is really poor, even installing one of them won't be possible without extroot.
Anyway, I temporary disabled it it and I still have the same issue!
I found a mitigation using SQM, but it's not a real solution though :frowning_face:

update: same issue after some time, even using SQM

4

Did you enable software offload?

1 Like
5

If you mean Routing/NAT Offloading in Firewall, yes, it's set to None.

6

What is that max speed that you get? It is only a single core MIPS CPU, and software tends to get larger and often slower as versions progress. SQM(*) and pppoe use a lot of CPU per packet.

Also which Archer C7 version? There were five of them though they have similar CPU but I'm not sure they were all 16/128 memory.

  • In other words, enabling SQM is going to make the problem of running out of CPU with a high ISP speed worse. But as a workaround for not having a faster router, you could set the SQM to much less than the ISP contract speed. Then there is usually an overall better Internet experience due to less buffer problems but of course you're not using the speed that you're paying for.
7

V1 V2 has 2 MII-s between SoC and switch, some has detachable antennas, but SoC is identical for the rest.

1 Like
8

Only the v1 is different, in the sense of 8/128 and an unsupported 5 GHz radio (qca9880-ar1a; in other words you would not want to use v1 with OpenWrt at all), all others can be treated alike (720 MHz QCA9558 --> 750 MHz QCA9563 in >=v4 can be ignored for all practical intents and purposes).

9

I have V5.
For sure I'll remove the SQM then, the issue is still existing without though

10

QoS == SQM?

2 Likes