On Thu, Mar 7, 2013 at 11:54 PM, YongHyeon PYUN <pyu...@gmail.com> wrote:
> On Fri, Mar 08, 2013 at 02:10:41AM -0500, Garrett Wollman wrote: > > I have a machine (actually six of them) with an Intel dual-10G NIC on > > the motherboard. Two of them (so far) are connected to a network > > using jumbo frames, with an MTU a little under 9k, so the ixgbe driver > > allocates 32,000 9k clusters for its receive rings. I have noticed, > > on the machine that is an active NFS server, that it can get into a > > state where allocating more 9k clusters fails (as reflected in the > > mbuf failure counters) at a utilization far lower than the configured > > limits -- in fact, quite close to the number allocated by the driver > > for its rx ring. Eventually, network traffic grinds completely to a > > halt, and if one of the interfaces is administratively downed, it > > cannot be brought back up again. There's generally plenty of physical > > memory free (at least two or three GB). > > > > There are no console messages generated to indicate what is going on, > > and overall UMA usage doesn't look extreme. I'm guessing that this is > > a result of kernel memory fragmentation, although I'm a little bit > > unclear as to how this actually comes about. I am assuming that this > > hardware has only limited scatter-gather capability and can't receive > > a single packet into multiple buffers of a smaller size, which would > > reduce the requirement for two-and-a-quarter consecutive pages of KVA > > for each packet. In actual usage, most of our clients aren't on a > > jumbo network, so most of the time, all the packets will fit into a > > normal 2k cluster, and we've never observed this issue when the > > *server* is on a non-jumbo network. > > > > AFAIK all Intel controllers generate jumbo frame by concatenating > multiple mbufs on RX side so there is no physically contiguous 9KB > allocation. I vaguely guess there could be mbuf leakage when jumbo > frame is enabled. I would check how driver handles mbuf shortage or > frame errors while mbuf concatenation for jumbo frame is in > progress. > No, this is not true, if using a 9K jumbo it will actually use the larger mbuf pool, the code has been this way for a little while now. Jack > > > Does anyone have suggestions for dealing with this issue? Will > > increasing the amount of KVA (to, say, twice physical memory) help > > things? It seems to me like a bug that these large packets don't have > > their own submap to ensure that allocation is always possible when > > sufficient physical pages are available. > > > > -GAWollman > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
