netdev - Re: questions on NAPI processing latency and dropped network packets

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Message-ID: <478BBFE3.9030707@nortel.com>
Date:	Mon, 14 Jan 2008 14:02:43 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	Eric Dumazet <dada1@...mosbay.com>
CC:	Ray Lee <ray-lk@...rabbit.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: questions on NAPI processing latency and dropped network packets

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.

Chris
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