Skip to contentSkip to conversation

ksoftirqd_CPU0 spinning in 2.4.21-pre3

DISCUSSION Ben Greear 2 participants 4 messages Jan 22, 2003 – Jan 24, 2003

lore
Share & tools
lore

Ben Greear

author
#0 lore raw

I happened to notice that my ksoftirqd_CPU0 process started spinning at 99% CPU when I plugged in the ports to a tulip NIC. I didn't see any significant amount of interrupts when I looked at /proc/interrupts, and there was no traffic running.

However, this is also running a hacked up tulip-napi driver, so it could very well be my problem. I have not seen this on any other kernel in several months though...

Anyway, if anyone has seen this, I'd like to know. Otherwise, I'll blame my code and start poking at things...

Thanks,
Ben

Signature · 3 lines
Ben Greear <[email protected]>       <Ben_Greear AT excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear
#1 lore raw
Quoted 11 lines · Ben Greear

I happened to notice that my ksoftirqd_CPU0 process started spinning at 99% CPU when I plugged in the ports to a tulip NIC. I didn't see any significant amount of interrupts when I looked at /proc/interrupts, and there was no traffic running.

However, this is also running a hacked up tulip-napi driver, so it could very well be my problem. I have not seen this on any other kernel in several months though...

Anyway, if anyone has seen this, I'd like to know. Otherwise, I'll blame my code and start poking at things...

Well it can be normal operation if box is highly loaded...

At high loads network interrupts are disabled not to trash performance or DoS the kernel. Which in turn does succesive polls via RX-softirq to devices at rate the it can process. So no interrupts when resources are scarce.

The lack of interrupts makes ksoftirqd run the RX-softirq so the network load becomes visable here. Also review the discussion about ksoftirqd priority.

Cheers.

							--ro
author
#2 lore raw
Quoted 6 lines · Robert Olsson
Quoted 5 lines · Ben Greear

I happened to notice that my ksoftirqd_CPU0 process started spinning at 99% CPU when I plugged in the ports to a tulip NIC. I didn't see any significant amount of interrupts when I looked at /proc/interrupts, and there was no traffic running.

Quoted 8 lines
Quoted 6 lines

However, this is also running a hacked up tulip-napi driver, so it could very well be my problem. I have not seen this on any other kernel in several months though...

Anyway, if anyone has seen this, I'd like to know. Otherwise, I'll blame my code and start poking at things...

Well it can be normal operation if box is highly loaded...

There was zero network load on the box. I think there must be a bug in my napi-ization of the tulip driver. Since I coppied it almost verbatim from your stuff, you might want to check too :)

Ben

Signature · 3 lines
Ben Greear <[email protected]>       <Ben_Greear AT excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear
#3 lore raw
Quoted 3 lines · Ben Greear

There was zero network load on the box. I think there must be a bug in my napi-ization of the tulip driver. Since I coppied it almost verbatim from your stuff, you might want to check too :)

If there are no interrupts and ksoftirqd is spinning it smells like dev->poll never calls netif_rx_complete() --> pure polling.

Cheers.

						--ro