very few ports from accessing our site.
I am not sure why the iptables_nat module would be loaded
because we are not using NAT in our network configuration, at least we
are
not intending to do so.
Well if you don't need it then just try and remove the NAT module using "modprobe -r
iptable_nat". And see if that makes any difference.
Can't remove it, get the message
"module is in use".. not sure by what.
Now the issue about MAX_SKBUFF_ORDER should only show up when you are
trying to send large packets. Do you use jumbo frames or something like
that? What MTU sizes are set for the interfaces? As far as I know the
message you get means that Xen is trying to allocate a buffer for the
packet to send, but the packet size is too big for the buffer
allocator.
[root@fg3x3 ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:16:3E:05:03:03
inet addr:131.225.107.144 Bcast:131.225.107.255
Mask:255.255.255.0
inet6 addr: fe80::216:3eff:fe05:303/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2971214615 errors:0 dropped:0 overruns:0 frame:0
TX packets:1576876803 errors:0 dropped:0 overruns:0
carrier:0
collisions:0 txqueuelen:1000
RX bytes:2428856680 (2.2 GiB) TX bytes:4068069258 (3.7 GiB)
No--no jumbo frames anywhere. MTU size is the standard 1500.
This is on all Dom0/DomU frontend and backend interfaces?
That's right.
In general, you can configure the Xen kernel to use a Xen-specific
buffer allocator, or the kernel's default buffer allocator. There is a
kernel configuration option for that and it is called
CONFIG_XEN_SKBUFF. You could try and switch that off, and recompile the
kernel.
So CONFIG_XEN_SKBUFF is by default on?
CONFIG_XEN_SKBUFF is on in my config.
There is no MAX_SKBUFF_ORDER parameter anywhere in my source tree,
much less the config file.
Steve Timm
I don't know for sure. It depends on your distro and whatever kernel you use.
You can check this in your kernel config files or eventually by looking at
/proc/config.gz. It depends on the Xen version etc, I don't know that by heart.
Also, the value of MAX_SKBUFF_ORDER depends on your kernel configuration and
memory options.
Looking at your megasas error message, I suspect that this is simply
because your system is running under high load and it is probably
running out of memory in various places. Maybe that is also the root
cause for the skbuff problem. What does Xen tell you about the memory
utilization, and how do you allocate your memory to DomU/Dom0?
This is a dell poweredge 2950 with 16 GB of RAM overall. 2GB for dom0,
[root@fermigrid3 ~]# free
total used free shared buffers
cached
Mem: 2156544 1218036 938508 0 242084
434092
-/+ buffers/cache: 541860 1614684
Swap: 24579440 0 24579440
4GB for this domU.
[root@fg3x3 ~]# free
total used free shared buffers
cached
Mem: 4096176 4073044 23132 0 33024
3130072
-/+ buffers/cache: 909948 3186228
Swap: 8191992 48 8191944
4 other domU's on this system but they are mostly idle.
Can you post an output of /proc/slabinfo of your DomU/Dom0 under high load?
Kernel config and slabinfo are posted.
--
------------------------------------------------------------------
Steven C. Timm, Ph.D (630) 840-8525
timm@xxxxxxxx http://home.fnal.gov/~timm/
Fermilab Computing Division, Scientific Computing Facilities,
Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.
slabinfo.fermigrid3
Description: Text document
slabinfo.fg3x3
Description: Text document
fg3x3.config
Description: Text document
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