Re: [PATCH 3/3] Convert the UDP hash lock to RCU

[Corey Minyard]

David Miller wrote:
> From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
> Date: Mon, 06 Oct 2008 23:22:31 +0200
>
>   
> > Me wondering what impact this synchronize_rcu() can have on mono-threaded
> > VOIP applications using lot of UDP sockets. What is the maximum delay of
> > this function ?
> >     
>
> The cost is enormous, we really can't use it here.
>
> I have a patch that did top-level socket destruction using RCU,
> and that didn't use synchronize_rcu(), and that killed connection
> rates by up to %20.
>
> I can only imagine what the cost would be if I had to add such a call
> in there.
>
> Really, I can't consider these changes seriously, as-is.
>
>   
Would using SLAB_DESTROY_BY_RCU be ok, or would that be too expensive?

-corey
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