RE: Serious performance issues

RE: Serious performance issues

[Ian Pratt]

> Also, note that I can get the same problem with bridging:
> 
> lots of timer interrupts
> ip li set dev br0 down --> timer gets 30/s
> ip li set dev br0 up --> timer goes crazy

I certainly don't see this on any of my systems.

Are you using the standard bridging scripts? I guess not since your
bridge name is different. The only time I've seen something like this is
when some of the bridge timeout parameters are set to 0 jiffies (setting
to 1 jiffy is OK).

Ian


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Re: Serious performance issues

[Tommi Virtanen]

Ian Pratt wrote:
> Are you using the standard bridging scripts? I guess not since your
> bridge name is different. The only time I've seen something like this is
> when some of the bridge timeout parameters are set to 0 jiffies (setting
> to 1 jiffy is OK).

I'm not. I had a fully working UML setup and wanted to share that
between UML and Xen.

The 0 jiffie thing was a good hint. That was the problem with bridge.
I'm guessing I had that issue all along with my native linux setup.

Summary:

Problem #1: plugging in my Logitech USB trackball creates an uhci_hcd
and timer interrupt storm that degrades performance to about 10% of
normal. Unplug does not stop storm. Unknown cause, not fixed, workaround
is not to plug in any USB device except hubs.

Problem #2: bridge setfd/sethello 0 causes timer interrupt storm, but
does not degrade performance significantly. Workaround is to not set
such low numbers. Will talk to brctl/bridging maintainers to make it
more foolproof.


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Re: Serious performance issues

[Nuutti Kotivuori]

Tommi Virtanen wrote:
> Problem #2: bridge setfd/sethello 0 causes timer interrupt storm,
> but does not degrade performance significantly. Workaround is to not
> set such low numbers. Will talk to brctl/bridging maintainers to
> make it more foolproof.

This is really odd. We run a lot of bridges with such settings. Or, to
be specific, for us, 'setfd' is always 0, 'setageing' is either 0 or
300, depending if we want the bridge to act as a 'hub' or not. STP is
always off.

Under these circumstances, we have never seen a timer interrupt
storm. But perhaps it is particular to having STP on.

-- Naked




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Re: Re: Serious performance issues

[B.G. Bruce]

Can you do a "lspci -v" as root and see if there is any correlation
between your network adapters and your usb devices?  (same interrupt) or
something.

Thanks,
B.



On Mon, 2005-03-07 at 15:19, Nuutti Kotivuori wrote:
> Tommi Virtanen wrote:
> > Problem #2: bridge setfd/sethello 0 causes timer interrupt storm,
> > but does not degrade performance significantly. Workaround is to not
> > set such low numbers. Will talk to brctl/bridging maintainers to
> > make it more foolproof.
> 
> This is really odd. We run a lot of bridges with such settings. Or, to
> be specific, for us, 'setfd' is always 0, 'setageing' is either 0 or
> 300, depending if we want the bridge to act as a 'hub' or not. STP is
> always off.
> 
> Under these circumstances, we have never seen a timer interrupt
> storm. But perhaps it is particular to having STP on.
> 
> -- Naked
> 
> 
> 
> 
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