Rui Machado wrote:
2008/5/17 Dotan Barak <[EMAIL PROTECTED]>:
Rui Machado wrote:
2008/5/16 Roland Dreier <[EMAIL PROTECTED]>:
> hmm..... and is there no workaround for this, for this situation? I
> mean, if the server dies isn't there any possibility that
> the sender/client realizes this. If the timeout it's too large this
> can be cumbersome.
>
> I tried reducing the timeout and indeed the client realizes faster
> when the server exits but another problem arises: Without exiting the
> server,
> on the client side I get the error (retry exceed) when polling for a
> recently posted send - this after some hours.
There's a tradeoff between detecting real failures faster, and reducing
false errors detected because a response came too slowly.
Clearly if a response may take an amount of time 'X' to be received
under normal conditions, there's no way to conclude that the remote side
has failed without waiting at least 'X'.
I understand. So there's no really difference between the two
situations, real server failure or just a load problem that takes more
time?
From the sender QP point of view, they are the same (ack/nack wasn't send
during a specific
period of time)
Something like a different error or a SIGPIPE :) ?
I will describe my situation, maybe it helps (bare with me as I'm
starting with Infiniband and so on)
I have a client and a server.The clients posts RDMA calls one at a
time (post, poll, post...). So server is just there.
If I try to start something like 16 clients on 1 machine, after a few
hours I will get an error on some client programs (retry excess) with
a timeout of 14. If I increase the timeout for 32, I don't see that
error but if I stop the server, the clients take a lot of time to
acknowledge that, which is also not wanted.
That's why I asked if there a 'good value'. If I have such a load
between 2 nodes, I always have to risk that if the server dies the
client will take much time to see it. That's not nice!
Did you try to increase the retry_count too?
(and not only the timeout).
Yes.
But that wouldn't change my scenario since the overall time is given
by the timeout * retry count right?
By the way, Which RDMA operation do you execute READ or WRITE?
READ.
Can you replace it with a write (from the other side)?
READ has "higher price" than a WRITE.
Anyway, you should get the mentioned behavior anyway..
When the sender get the error, what is the status of the receiver QP?
(did you try to execute ibv_query_qp and get its status?)
Dotan
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