netdev - Re: [net-next PATCH V3-evictor] net: frag evictor, avoid killing warm frag queues

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Message-ID: <20121206123248.GA24493@breakpoint.cc>
Date:	Thu, 6 Dec 2012 13:32:48 +0100
From:	Florian Westphal <fw@...len.de>
To:	Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
	Thomas Graf <tgraf@...g.ch>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Cong Wang <amwang@...hat.com>,
	Herbert Xu <herbert@...dor.hengli.com.au>
Subject: Re: [net-next PATCH V3-evictor] net: frag evictor, avoid killing
 warm frag queues

Jesper Dangaard Brouer <jbrouer@...hat.com> wrote:
> CPUs are fighting for the same LRU head (inet_frag_queue) element,
> which is bad for scalability.  We could fix this by unlinking the
> element once a CPU graps it, but it would require us to change a
> read_lock to a write_lock, thus we might not gain much performance.
> 
> I already (implicit) fix this is a later patch, where I'm moving the
> LRU lists to be per CPU.  So, I don't know if it's worth fixing.

Do you think its worth trying to remove the lru list altogether and
just evict from the hash in a round-robin fashion instead?
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