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Re: What would it take....

From: Da Zheng
Subject: Re: What would it take....
Date: Tue, 22 Dec 2009 23:04:55 +0800
User-agent: Thunderbird (Macintosh/20090812)

Samuel Thibault wrote:
>> If Hurd's RPCs have to be used when we synchronize relevant operations, we 
>> might not get any benefit by using shared memory.
> You do not need RPCs all the time, just when starting/finishing
> processing items. While processing others can arrive and will get
> processed without the need for another RPC, but when work is done,
> everybody needs to somehow wait for next signal. You should probably
> read about Xen's ring mecanism.
I think I quite understand wait/signal processing. I think there are two types 
of synchronization in this case. One is the network driver needs to send a 
wakeup signal to pfinet when receiving a packet if pfinet is waiting for 
packets. The other one is that the driver and pfinet somehow need to be 
synchronized when they modified shared variables such as the queue length. For 
the latter one, I think we need to use process-shared mutexes, which is what I 
meant in the beginning. When we protect the shared variable with a mutex, I 
don't think we need to use RPCs to synchronize two processes, right?

Zheng Da

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