[Beowulf] PVM on wireless...
Robert G. Brown
rgb at phy.duke.edu
Wed Feb 6 13:28:24 PST 2008
On Wed, 6 Feb 2008, Reuti wrote:
> Just an idea to check: PVM can also be started without rsh/ssh between the
> machines. You have to copy and paste some things from here to there and back
> and can startup all daemons this way by hand (page 30 in the PVM book). Maybe
> this works - just to narrow the cause.
I'll look into this, thanks, although the daemon IS started -- the block
it is somewhere after that. But it is well worth trying anyway.
I also wonder about ports and WAP interactions. I've got my WAP
configured (AFAICT) as an internal switch, not really as a router. As
in my laptop get DCHP service from my linux server, not the WAP, which
is flat to broadcasts, has no port filtering on the internal network
I even ran tcpdump on the problem last time it happened -- maybe I
should try it again.
> -- Reuti
>> I suspect a race condition, probably caused by using raw UDP with some
>> assumption of latency during the handshake. The one way I can think of
>> that the two connections differ is in their latency -- even the
>> bandwidth of wireless is every bit as great as 10B2 networks I've run
>> PVM on in years past (on proportionally slower CPUs, of course). If the
>> master or slave send out an acknowledgement packet either before the
>> window where the other can receive it or after it has grown bored and
>> stopped listening, it might fail to properly bind or something. It
>> seems like it would be a bug, not a feature, but if I were feeling
>> infinitely masochistic and were to wander down into Other People's
>> Source (ouch!) to try to debug this, that's what I'd look for first.
>> Any PVM developers still on list? Any comments from them?
>>> Just a thought,
>>> On Feb 6, 2008, at 10:40 AM, Robert G. Brown wrote:
>>>> Anybody on list have any idea why PVM fails to add hosts over a wireless
>>>> link? I've now tried this over multiple distro version and at least one
>>>> PVM update, and it just doesn't work. Works fine over a wire, fails on
>>>> wireless, and as far as I know wire and wireless are both "identical"
>>>> at the kernel interface layer so that any e.g. socket one might open is
>>>> absolutely ecumenical about what the underlying hardware is (good old
>>>> ISO/OSI layering, right?).
>> Robert G. Brown Phone(cell): 1-919-280-8443
>> Duke University Physics Dept, Box 90305
>> Durham, N.C. 27708-0305
>> Web: http://www.phy.duke.edu/~rgb
>> Book of Lilith Website: http://www.phy.duke.edu/~rgb/Lilith/Lilith.php
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Robert G. Brown Phone(cell): 1-919-280-8443
Duke University Physics Dept, Box 90305
Durham, N.C. 27708-0305
Book of Lilith Website: http://www.phy.duke.edu/~rgb/Lilith/Lilith.php
Lulu Bookstore: http://stores.lulu.com/store.php?fAcctID=877977
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