Re: Random mbuf corruption

[Paul Barrette <paul.barrette-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org>]

On 06/20/2014 07:20 AM, Stefan Baranoff wrote:
> All,
>
> We are seeing 'random' memory corruption in mbufs coming from the ixgbe UIO
> driver and I am looking for some pointers on debugging it. Our software was
> running flawlessly for weeks at a time on our old Westmere systems (CentOS
> 6.4) but since moving to a new Sandy Bridge v2 server (also CentOS 6.4) it
> runs for 1-2 minutes and then at least one mbuf is overwritten with
> arbitrary data (pointers/lengths/RSS value/num segs/etc. are all
> ridiculous). Both servers are using the 82599EB chipset (x520) and the DPDK
> version (1.6.0r2) is identical. We recently also tested on a third server
> running RHEL 6.4 with the same hardware as the failing Sandy Bridge based
> system and it is fine (days of runtime no failures).
>
> Running all of this in GDB with 'record' enabled and setting a watchpoint
> on the address which contains the corrupted data and executing a
> 'reverse-continue' never hits the watchpoint [GDB newbie here -- assuming
> 'watch *(uint64_t*)0x7FB.....' should work]. My first thought was memory
> corruption but the BIOS memcheck on the ECC RAM shows no issues.
>
> Also looking at mbuf->pkt.data, as an example, the corrupt value was the
> same 6/12 trials but I could not find that value elsewhere in the processes
> memory. This doesn't seem "random" and points to a software bug but I
> cannot for the life of me get GDB to tell me where the program is when that
> memory is written to. Incidentally trying this with the PCAP driver and
> --no-huge to run valgrind shows no memory access errors/uninitialized
> values/etc.
>
> Thoughts? Pointers? Ways to rule in/out hardware other than going 1 by 1
> removing each of the 24 DIMMs?
>
> Thanks so much in advance!
> Stefan
Run memtest to rule out bad ram.

Pb