Re: questions on NAPI processing latency and dropped network packets

[Vlad Yasevich]

Chris Friesen wrote:
> Eric Dumazet wrote:
> > Chris Friesen a Ãcrit :
>
> > > Based on the profiling information we're spending time in 
> > > sctp_endpoint_lookup_assoc() which doesn't actually use hashes, so I 
> > > can't see how the hash would be related.  I'm pretty new to SCTP 
> > > though, so I may be missing something.
> >
> > Well, it does use hashes :)
> >
> >        hash = sctp_assoc_hashfn(ep->base.bind_addr.port, rport);
> >        head = &sctp_assoc_hashtable[hash];
> >        read_lock(&head->lock);
> >        sctp_for_each_hentry(epb, node, &head->chain) {
> >            /* maybe your machine is traversing here a *really* long 
> > chain */
> >            }
>
>
> The latest released kernel doesn't have this code, it was only added in 
> November.  The SCTP maintainer just pointed me to the patch, and made 
> some other suggestions as well.

Yes,  the hash code only got added to 2.6.24.  Before that, it was
a linear list traversal which sucked.

I need to take a look at the locking to see if we can further reduce
the time that bottom half is disabled.

-vlad
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