Messages in this thread | | | Subject | Re: [PATCH 3/3] Convert the UDP hash lock to RCU | From | Peter Zijlstra <> | Date | Tue, 07 Oct 2008 10:31:30 +0200 |
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On Mon, 2008-10-06 at 14:40 -0700, David Miller wrote: > From: Eric Dumazet <dada1@cosmosbay.com> > 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.
Did you ever figure out why you lost those 20% ?
> I can only imagine what the cost would be if I had to add such a call > in there.
Yeah, sync_rcu() is rediculously expensive, at best 3 jiffies IIRC.
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