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Opened 6 years ago

Last modified 3 years ago

#11178 reopened defect

b43: excessive cpu load in [irq/5-b43]

Reported by: vitor.dominor@… Owned by: developers
Priority: normal Milestone: Barrier Breaker 14.07
Component: packages Version: Trunk
Keywords: Cc:

Description

In Asus WL-520GU with the wireless b43 driver, when doing some network intensive activity like a download through the wireless, the process [irq/5-b43] shows excessive cpu usage (monitored by top) between 20-40%.

Attachments (0)

Change History (19)

comment:1 in reply to: ↑ description Changed 6 years ago by vitor.dominor@…

Replying to vitor.dominor@…:

In Asus WL-520GU with the wireless b43 driver, when doing some network intensive activity like a download through the wireless, the process [irq/5-b43] shows excessive cpu usage (monitored by top) between 20-40%.

Latest stable firmware is being used version 666.2, with trunk r31059.

comment:2 Changed 6 years ago by nbd

  • Resolution set to worksforme
  • Status changed from new to closed

That's normal. The CPU has to do some stuff in IRQ context in order to handle network traffic, and the CPU is not that fast...

comment:3 Changed 6 years ago by vitor.dominor@…

I already suspected that. I just wasn't sure it it was abnormal behavior. Upon further testing, the results seem to confirm that.
This time, I switched my router to a TomatoUSB Toastman build, which uses the broadcom proprietary binary driver for wireless and when doing a download at maximum speed available, through the wireless, top attributes cpu usage to irq or ksoftirqd/0, from 20% to 50%, with some peaks of 80% and after some time, the router becomes sluggish in telnet. However, I still note a difference regarding the b43 driver in OpenWRT. With the b43 driver and the aforementioned kernel process handling IRQ stuff, I note a slight decrease in download performance, meaning that the download does not stay constant at maximum speed (being the only cpu intensive task at the moment), while with the proprietary broadcom driver despite equivalent intensive irq load on the cpu, the same download stays constantly at maximum speed.

comment:4 Changed 5 years ago by pupykin.s@…

It can be reproduced on asus wl500gp2 with 3.3 kernel and current 3.6.11 from openwrt trunk.

comment:5 Changed 5 years ago by pupykin.s@…

There is no wifi connection at this time and router becomes unusable until reboot. Can not guess yet which external conditions are needed to reproduce it.

comment:6 follow-up: Changed 5 years ago by anonymous

  • Resolution worksforme deleted
  • Status changed from closed to reopened

actually I use wrt54gl and openwrt 12.09 and I have the same problem when calling "wifi down" and "wifi" to re-enable wifi. the cpu load goes up to 99% of this driver and the router is not usable at all. I haven't tried propritary driver yet.

comment:7 in reply to: ↑ 6 Changed 5 years ago by anonymous

Replying to anonymous:
some more note: after a while I have an out-of-memory an the router reboots.

comment:8 Changed 5 years ago by hauke

  • Resolution set to worksforme
  • Status changed from reopened to closed

The wrt54gl has a slow CPU and why should we not use the CPU power when we need like in wifi down && wifi up? The wrt54gl also just has 16MB ram which will cause problems.

comment:9 Changed 5 years ago by anonymous

I solved my case using

brctl stp br-lan on

command. Have no guess how loop detection can resolve this issue.

comment:10 Changed 5 years ago by hauke

What problem did you resolve with this command?
The out of memory problem or the CPU usage problem?

comment:11 Changed 4 years ago by anonymous

I think mostly out of memory problem, but I did not measure CPU usage carefuly yet.

comment:12 Changed 4 years ago by anonymous

Sorry,I'm Chinese
My Englist very is poor


I have encountered such a problem,OpenWRT version is 12.09,
When I use Aria2,"irq" load very high 50%+
I hope ,this problem can solve,
Or change Linux IRQ mechanism

comment:13 Changed 4 years ago by testuser12@…

Sorry,I'm Chinese
My Englist very is poor


I have encountered such a problem,OpenWRT version is 12.09,
When I use Aria2,"irq" load very high 50%+
I hope ,this problem can solve,
Or change Linux IRQ mechanism

comment:14 Changed 4 years ago by testuser12@…

Sorry,I'm Chinese
My Englist very is poor


I have encountered such a problem,OpenWRT version is 12.09,
When I use Aria2,"irq" load very high 50%+
I hope ,this problem can solve,
Or change Linux IRQ mechanism

comment:15 Changed 4 years ago by MarcoGamberoni

Can confirm the bug in Attitude Adjustment 12.09 r36088 on a BCM63xx board with 16MB memory.
Trigger with

/etc/init.d/network restart

high cpu utilization by b43 irq follows. OOM kill and watchdog restart can follow.
CPU utilization returns normal with

ctrl+c # regain shell prompt
rmmod b43
insmod b43

After reinserting the module, restarting network works IN THE ONE TEST PERFORMED.
Memory limit could be an explanation, but I dare to say the boot instance of b43 keeps some reference to _ _init memory which makes it misbehave on restart.


Last edited 4 years ago by MarcoGamberoni (previous) (diff)

comment:16 Changed 4 years ago by MarcoGamberoni

  • Resolution worksforme deleted
  • Status changed from closed to reopened

comment:17 Changed 4 years ago by jow

  • Milestone changed from Attitude Adjustment 12.09 to Barrier Breaker 14.07

Milestone Attitude Adjustment 12.09 deleted

comment:18 Changed 3 years ago by anonymous

Confirmed this problem still exists in trunk. Older versions of b43 were much more usable, the current version must have a problem.

comment:19 Changed 3 years ago by beatstream

I confirm that problem on my RTN16.
Just remove old driver kmod-b43 and install broadcom-wl, nas and wl|wlc. With that proprietary driver speed over wifi increases from ~1MBps to ~2.5MBps, while cpu load decreases from 2-2.5 to <1 (and this is with transmission client).
I know that this is not solving the problem as is, but if u want more stability and speed, it will help.

Last edited 3 years ago by beatstream (previous) (diff)

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