Re: mode connected infiniband

[Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>]

 > I'll contribute my 2c here, as I have experienced some page allocation
 > errors in the past when using drbd and cm. I think drbd in particular
 > might trigger it since it's pushes a lot of data through the link, but
 > regardless the circumstances are somewhat difficult to replicate. I'm not
 > completely certain they are relevant, but here are some of the traces that
 > I've noticed then; these were observed on some version of OFED 1.4 if I
 > recall. Setting /proc/sys/vm/min_free_kbytes to some ridiculous number does
 > work around this.
 > 
 > http://www.mail-archive.com/drbd-user-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org/msg00441.html
 > http://lists.linbit.com/pipermail/drbd-user/2009-April/011880.html

Thanks.  I notice that neither of these tracebacks actually have any
IPoIB functions (or indeed anything RDMA-related).  So it seems the
problem is probably somewhere more generic, triggered by the large MTU
allowed by IPoIB CM.

One traceback starts with

    drbd0_worker: page allocation failure. order:5, mode:0x10

so someone is trying to do an order 5 allocation on the send path.  And
the other one starts with

    drbd0_receiver: page allocation failure. order:4, mode:0x20

So similarly, the receive path is trying an order 4 allocation.

Are both of these tracebacks using IPoIB CM with a ~64K MTU?

 - R.

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