netdev - Re: [PATCH 0/5] Long term PMTU/redirect storage in ipv4.

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Message-ID: <1342596648.2626.1831.camel@edumazet-glaptop>
Date:	Wed, 18 Jul 2012 09:30:48 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Julian Anastasov <ja@....bg>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 0/5] Long term PMTU/redirect storage in ipv4.

On Wed, 2012-07-18 at 10:28 +0300, Julian Anastasov wrote:

> 	This is going to read all values in the chain
> before reaching daddr? Or may be FNHE_RECLAIM_DEPTH is
> small and nobody will increase it. May be I can create
> some func that searches daddr in chain instead. Do you still
> prefer to remove the first daddr check or it is only
> that the code is intended too much?
> 

I would not bother, since real cost is the initial cache line miss.
Once you read one field, reading others is really fast.

> > +		if (fnhe_daddr == daddr) {
> 
> 	Also, do we need some rcu locking in
> __ip_rt_update_pmtu or may be ipv4_update_pmtu is
> called always under rcu lock?

Sorry, I dont understand, we use the full lock
write_seqlock_bh(&fnhe_seqlock);/write_sequnlock_bh(&fnhe_seqlock);

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