Subject: Re: [PATCH 00/28] Swap over NFS -v16
From: Peter Zijlstra <peterz@infradead.org>
To: Neil Brown <neilb@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       netdev@vger.kernel.org, trond.myklebust@fys.uio.no,
       Pekka Enberg <penberg@cs.helsinki.fi>
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Date: Fri, 07 Mar 2008 12:55:31 +0100
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On Fri, 2008-03-07 at 12:17 +0100, Peter Zijlstra wrote:

> That would be so if the whole path from RX to socket demux would have
> hard-irqs disabled. However I didn't see that. Moreover I think the
> whole purpose of the NetPoll interface is to allow some RX queueing to
> cut down on softirq overhead.

s/NetPoll/NAPI/

More specifically look at net/core/dev.c:netif_rx()
It has a input queue per device.

> >   2/ If the host is routing network packets, then incoming packets
> >      might go on an outbound queue.  Is this space limited?  and
> >      included in the reserve?
> 
> Not sure, somewhere along the routing code I lost it again. Constructive
> input from someone versed in that part of the kernel would be most
> welcome.

To clarify, I think we just send it on as I saw no reason why that could
fail. However the more fancy stuff like engress or QoS might spoil the
party, that is where I lost track.


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