Re: [BProc] page allocation problems

[Sean <se...@la...>]

HI
    I wrote the attached patch to ifdup.c that lets you set the mtu in 
beoboot quite some time ago.  I guess I should check it in.

Sean



Dale Harris 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, and
>>>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
>>    
>>
>
>
>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.  
>
>
>With bproc is can I just put a:
>
>plugin ifconfig myri0 mtu 4000
>
>
>To set the MTU when the nodes boot?  Or does it support setting the MTU?
>
>
>Dale
>
>
>
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