[Barrelfish-users] Messages

[Zeus Gómez Marmolejo]

Hi,

I discovered another surprising thing. I'm calling the function
messages_wait_and_handle_next() to wait and dispatch one message. Which in
turn calls to event_dispatch(). According to the info I get on screen,
sometimes it handles two messages before returning. This is strange.

I was inspecting the code and it's calling to get_next_event() which is
supposed to handle only one event from the waitset. I don't understand this
behavior, is this possible?

zeus.

El 17 de agosto de 2011 14:48, Zeus Gómez Marmolejo <zeus.gomez at bsc.es>escribió:

> Ok, I don't get any failures when sending messages, as I'm always checking
> with can_send(). Otherwise, I call the event_dispatch().
>
> But now I'm sure that messages get reordered somehow. It's difficult to
> send the code as it's quite involved, but I filled the code with some
> printf. I'm using own implemented barriers using the barrelfish message
> passing and I see the message handler that is in the barrier dispatching
> messages that were sent after the barrier reply. Then suddenly the message
> reply for the barrier arrives ... how can it be?
>
> I don't know how the stub is working but is it possible that is sending a
> retry of a message after the following message has been sent?
>
> zeus.
>
> El 13 de agosto de 2011 17:49, Timothy Roscoe <troscoe at inf.ethz.ch>escribió:
>
>
>> Well, messages should never be lost or reordered on a UMP channel, but
>> both sending and receiving messages can temporarily fail in a variety
>> of ways (we push retries due to full channels, etc. back to the
>> sender).
>>
>> This means that a single-threaded sender and receiver can deadlock if
>> they're not careful about handling things like send failures due to a
>> full channel, or the need to send acks back from the receiver.
>>
>> The stubs try to hide most of the functionality required for this,
>> except for the fact that any send or recv can fail (as with Unix NBIO
>> and select/poll).
>>
>> That said, you probably already know most of this :-)
>>
>> And, of course, there are probably bugs.
>>
>>  -- Mothy
>>
>> At Sat, 13 Aug 2011 15:08:27 +0200, Zeus Gómez Marmolejo <
>> zeus.gomez at bsc.es> wrote:
>> > I'm trying to simplify the code (I'm using all gasnet and the library I
>> > made), but whenever I get it simpler it turns out that it's working...
>> >
>> > So I have to figure out where the problem is.
>> >
>> >
>> > El 12 de agosto de 2011 11:43, Tim Harris (RESEARCH)
>> > <tharris at microsoft.com>escribió:
>> >
>> > >  Could you post some code examples?****
>> > >
>> > > ** **
>> > >
>> > > Cheers,****
>> > >
>> > > ** **
>> > >
>> > > Tim****
>> > >
>> > > ** **
>> > >
>> > > ** **
>> > >
>> > > ** **
>> > >
>> > > *From:* Zeus Gómez Marmolejo [mailto:zeus.gomez at bsc.es]
>> > > *Sent:* 12 August 2011 10:42
>> > > *To:* barrelfish-users at lists.inf.ethz.ch
>> > > *Subject:* [Barrelfish-users] Messages****
>> > >
>> > > ** **
>> > >
>> > > Hi,****
>> > >
>> > > ** **
>> > >
>> > > I'm developing a benchmark for message passing in Barrelfish, but I
>> don't
>> > > get it working properly. I experience some random errors. ****
>> > >
>> > > ** **
>> > >
>> > > The application is single threaded and it's using the flounder stubs
>> to
>> > > send messages via the UMP backend. Some of the messages get lost. Is
>> it
>> > > possible that they arrive in different order that they were sent? I'm
>> not
>> > > sure how to debug it****
>> > >
>> > > ** **
>> > >
>> > > ** **
>> > >
>> > > Thanks for your help!
>> > >
>> > > --
>> > > Zeus Gómez Marmolejo
>> > > Barcelona Supercomputing Center
>> > > PhD student
>> > > http://www.bsc.es
>> > >
>> > > ****
>> > >
>> >
>> >
>> >
>> > --
>> > Zeus Gómez Marmolejo
>> > Barcelona Supercomputing Center
>> > PhD student
>> > http://www.bsc.es
>> >
>>
>
>
>
> --
> Zeus Gómez Marmolejo
> Barcelona Supercomputing Center
> PhD student
> http://www.bsc.es
>
>
>


-- 
Zeus Gómez Marmolejo
Barcelona Supercomputing Center
PhD student
http://www.bsc.es
-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://lists.inf.ethz.ch/pipermail/barrelfish-users/attachments/20110817/1a8f9f9b/attachment.html