On 11/27/11 8:39 PM, YongHyeon PYUN wrote:
On Sat, Nov 26, 2011 at 04:05:58PM -0500, Mike Andrews wrote:
I have a Supermicro 5015A-H (Intel Atom 330) server with two Realtek
RTL8111C-GR gigabit NICs on it. As far as I can tell, these support
jumbo frames up to 7422 bytes. When running them at an MTU of 5000 on
Actually the maximum size is 6KB for RTL8111C, not 7422.
RTL8111C and newer PCIe based gigabit controllers no longer support
scattering a jumbo frame into multiple RX buffers so a single RX
buffer has to receive an entire jumbo frame. This adds more burden
to system because it has to allocate a jumbo frame even when it
receives a pure TCP ACK.
OK, that makes sense.
FreeBSD 9.0-RC2, after a week or so of update, with fairly light network
activity, the interfaces die with "no memory for jumbo buffers" errors
on the console. Unloading and reloading the driver (via serial console)
doesn't help; only rebooting seems to clear it up.
The jumbo code path is the same as normal MTU sized one so I think
possibility of leaking mbufs in driver is very low. And the
message "no memory for jumbo RX buffers" can only happen either
when you up the interface again or interface restart triggered by
watchdog timeout handler. I don't think you're seeing watchdog
timeouts though.
I'm fairly certain the interface isn't changing state when this happens
-- it just kinda spontaneously happens after a week or two, with no
interface up/down transitions. I don't see any watchdog messages when
this happens.
When you see "no memory for jumbo RX buffers" message, did you
check available mbuf pool?
Not yet, that's why I asked for debugging tips -- I'll do that the next
time this happens.
What's the best way to go about debugging this... which sysctl's should
I be looking at first? I have already tried raising kern.ipc.nmbjumbo9
to 16384 and it doesn't seem to help things... maybe prolonging it
slightly, but not by much. The problem is it takes a week or so to
reproduce the problem each time...
I vaguely guess it could be related with other subsystem which
leaks mbufs such that driver was not able to get more jumbo RX
buffers from system. For instance, r228016 would be worth to try on
your box. I can't clearly explain why em(4) does not suffer from
the issue though.
I've just this morning built a kernel with that fix, so we'll see how
that goes.
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