[Lustre-devel] SMP Scalability, MDS, reducing cpu pingpong

Oleg Drokin Oleg.Drokin at Sun.COM
Thu Jul 30 06:35:48 PDT 2009


On Jul 30, 2009, at 5:25 AM, Liang Zhen wrote:
>>>> Another scenario that I have not seen discussed but that is
>>>> potentially pretty important for MDS is ability to route expected
>>>> messages (the ones like rep-ack reply) to a specific cpu regardless
>>>> of what NID did it come from. E.g. if we did rescheduling of MDS
>>>> request to some CPU and this is a difficult reply, we definitely
>>>> want the confirmation to be processed on that same cpu that sent  
>>>> the
>>>> reply originally, since it references all the locks supposedly
>>>> served by that CPU, etc. This is better to happen within LNET. I
>>>> guess similar thing might be beneficial to clients too where a  
>>>> reply
>>>> is received on the same CPU that sent original request in hopes  
>>>> that
>>>> the cache is still valid and the processing would be so much faster
>>>> as a result.
>>> You could use a "hints" field in the LNET header for this.
> That's about outgoing LNet message when sending reply, however,  
> sending a message still need go through "connection" & "peer" of  
> LNet and LND as well, and finally go out from the connection of  
> network stack, which are all bound on CPU hashed by NID (again).

Nothing prevents us from introducing extra argument for event handler,  


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