Large amounts of memory access operations cause panic under CURRENT (was "Large gap between fwrite and write, and fread and read")

[youshi10 at u.washington.edu]

On Tue, 17 Jul 2007, Milos Vyletel wrote:

>>> Go figure it'd cause panics for other people.
>>>
>>> I wasn't using zfs at all but it panicked anyhow once (my amd64 VM only,
>>> not my i386 test server, surprisingly). I wish I'd gotten the panic but I
>>> walked away to get a glass of water, and there wasn't a core dump because
>>> the VM shut down completely instead of restarting. Heh.
>>>
>>> My virtual machine died around 90k on the first trial though. I'll be sure
>>> to reduce the amount and see what happens, and I'll put nanosleeps or
>>> usleeps between the read and write ops to see if that alleviates the race
>>> condition seen, but I'll keep the problem code around for reference later
>>> in case I've stimulated some sort of weird bug in FreeBSD, or otherwise.
>>>
>>> Both my VM and test server run almost no programs though other than samba
>>> and rsync, so you'll probably see the panic faster / more frequently than I
>>> will if you run a lot more programs resident in memory.
>>>
>>> Just curious, what scheduler are you using on CURRENT, what processor do
>>> you have, and what are your memory specs?
>>>
>>> Thanks,
>>> -Garrett
>>>
>> Hi Garrett,
>>
>> this is just my desktop where is running only Xorg, fluxbox, few aterms and
>> firefox. But i can get the panic on console too, shortly after booting. I'm
>> using SCHED_ULE.
>>
>> CPU: AMD Athlon(tm) 64 X2 Dual Core Processor 4200+ (2205.01-MHz K8-class
>> CPU)
>>   Origin = "AuthenticAMD"  Id = 0x20f32  Stepping = 2
>>   Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
>>   Features2=0x1<SSE3>
>>   AMD Features=0xe2500800<SYSCALL,NX,MMX+,FFXSR,LM,3DNow!+,3DNow!>
>>   AMD Features2=0x3<LAHF,CMP>
>>   Cores per package: 2
>> usable memory = 3211718656 (3062 MB)
>> avail memory  = 3105570816 (2961 MB)
>>
>> For the record, it crashes few times before it hit 100k iterations, before i
>> put
>> debug printf in your code and increase MAX_ITERATIONS to 1m. And as far as I
>> can tell, I had pretty much the same results as you've measured.
>>
>> mv
>
> Sorry for the noise, forgot to CC current@

This seems to be resolved with the latest CURRENT sources and ULE patches.

-Garrett