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SubjectRe: questions on NAPI processing latency and dropped network packets
Chris Friesen wrote:
> Eric Dumazet wrote:
>> Chris Friesen a écrit :
>
>>> 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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