[openib-general] [PATCH][1/7]ipoib performance patches -- remove ah_reap

[Shirley Ma]

Roland,

Roland Dreier <rdreier at cisco.com> wrote on 05/24/2006 02:03:34 PM:

>     Shirley> My observation is the atomic operation is not that
>     Shirley> expensive.
> 
> It's just about the worst thing to do.  For example, on x86/x86-64 an
> instruction with the lock; prefix is quite slow.  If you look at an
> instruction level profile you can see that quite clearly.

Compared to have a single thread handling AH, I don't think this atomic 
operation is expensive.

>     Shirley> I thought the path holding another AH reference to
>     Shirley> prevent it to be freed?
> 
> If that were true then why would we want to reference count sends at
> all?  The whole point is that a path might be destroyed before the
> send is executed.
> 
>  - R.

It is true for unicast, it has a reference count before ipoib_send(). I 
need to look at multicast.

Thanks
Shirley Ma
IBM Linux Technology Center
15300 SW Koll Parkway
Beaverton, OR 97006-6063
Phone(Fax): (503) 578-7638
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