Proposed 6.2 em RELEASE patch

Scott Long scottl at
Mon Nov 13 01:48:07 UTC 2006

Mike Tancsa wrote:
> At 11:41 AM 11/12/2006, Scott Long wrote:
>> Mike Tancsa wrote:
>>> At 01:42 AM 11/11/2006, Scott Long wrote:
>>> driver.  What will help me is if you can hook up a serial console to
>>>> your machine and see if it can be made to drop to the debugger while it
>>>> is under load and otherwise unresponsive.  If you can, getting a 
>>>> process
>>>> dump might help confirm where each CPU is spending its time.
>>> ./netblast 500 110 1000
>>> I compiled in the various debugging options and on the serial console 
>>> I get a few
>>> Expensive timeout(9) function: 0xc0601e48(0) 0.024135749 s
>>> and the serial console
>> One CPU seems to be stuck in softclock.  My guess here is that there 
>> is significant lock contention.  Please try the following:
>> 1. Use addr2line or gdb on the kernel to find out what function is at
>> 0xc0601e48 (the address that was printed above).  This address will
>> change every time you recompile the kernel, so you'll need to reacquire
>> it from the console each time.
> # addr2line 0xc0601e48 -e kernel.debug -f
> nfsrv_timer
> /usr/src/sys/nfsserver/nfs_srvsock.c:809
> #

Can you try removing NFS from your kernel?

> and
> # addr2line 0xc0561444 -e kernel.debug -f
> sleepq_timeout
> /usr/src/sys/kern/subr_sleepqueue.c:724

This is sched_lock contention.

> I dont have any nfs activity on the box
>> 2. Try compiling in WITNESS and running the test as before, then break
>> into the debugger as before.  Run 'show locks'.  I'm not sure how
>> fruitful this will be, WITNESS might make it unbearably slow.
> It was in that kernel already

So you're seeing the livelock under load while also having WITNESS 
enabled?  Have you tried your test without WITNESS?  What about INVARIANTS?


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