Re: [BProc] page allocation problems

[Erik H. <eah...@gm...>]

On 5/9/05, Dale Harris <ro...@ma...> wrote:
> On Mon, May 09, 2005 at 10:54:16AM -0700, Erik Hendriks elucidated:
> > On 5/7/05, Dale Harris <ro...@ma...> wrote:
> > >
> > > Hey I'm seeing some page allocation errors.  Has anyone seen anything
> > > like this.  Of course it a 2.6.9 vanilla kernel patched for bproc, an=
d
> > > myrinet GM driver is running.
> >
> > I don't think this has anything to do with BProc per se.  I've seen
> > stuff like this before whenever I turn on jumbo frames on any machine
> > and start shoving a lot of data through.  I'm not 100% sure I'm right
> > about what's going on but here's my guess:
> >
> > Once you start using jumbo frame sizes (~9k) it gets harder to
> > allocate skuffs in the kernel.  These are the buffers that hold
> > network packets.  Pages for this kind of stuff are allocated in powers
> > of two.  9k will require 4 pages.  Also, since it's kernel space stuff
>=20
> Okay, so this does make sense.  Myrinet is using Jumbo frames and set
> itself to a default of MTU of 9000.  Myrinet suggested dropping the
> frame size down to 4000.
>=20
> With bproc is can I just put a:
>=20
> plugin ifconfig myri0 mtu 4000
>=20
> To set the MTU when the nodes boot?  Or does it support setting the MTU?

It doesn't although it certainly should...  There's code in the ifdup
beoboot module to do it.  That could probably be copied to the
ifconfig module without too much trouble.

- Erik