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From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Ben Hutchings <bhutchings@solarflare.com>
Cc: Jesper Dangaard Brouer <jbrouer@redhat.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	netdev@vger.kernel.org, yoshfuji@linux-ipv6.org
Subject: Re: RFC crap-patch [PATCH] net: Per CPU separate frag mem accounting
Date: Fri, 15 Mar 2013 00:12:50 +0100	[thread overview]
Message-ID: <20130314231250.GA7974@order.stressinduktion.org> (raw)
In-Reply-To: <1363294743.2695.10.camel@bwh-desktop.uk.solarflarecom.com>

On Thu, Mar 14, 2013 at 08:59:03PM +0000, Ben Hutchings wrote:
> On Thu, 2013-03-14 at 09:59 +0100, Jesper Dangaard Brouer wrote:
> > On Thu, 2013-03-14 at 08:25 +0100, Jesper Dangaard Brouer wrote:
> > > This is NOT the patch I just mentioned in the other thread, of removing
> > > the LRU list.  This patch does real per cpu mem acct, and LRU per CPU.
> > > 
> > > I get really good performance number with this patch, but I still think
> > > this might not be the correct solution.
> > 
> > The reason is this depend on fragments entering the same HW queue, some
> > NICs might not put the first fragment (which have the full header
> > tuples) and the remaining fragments on the same queue. In which case
> > this patch will loose its performance gain.
> [...]
> 
> The Microsoft RSS spec only includes port numbers in the flow hash for
> TCP, presumably because TCP avoids IP fragmentation whereas datagram
> protocols cannot.  Some Linux drivers allow UDP ports to be included in
> the flow hash but I don't think this is the default for any of them.
> 
> In Solarflare hardware the IPv4 MF bit inhibits layer 4 flow steering,
> so all fragments will be unsteered.  I don't know whether everyone else
> got that right though. :-)

Shouldn't they be steered by the IPv4 2-tuple then (if ipv4 hashing is enabled
on the card)?

  reply	other threads:[~2013-03-14 23:12 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20130308221647.5312.33631.stgit@dragon>
     [not found] ` <20130308221744.5312.14924.stgit@dragon>
2013-03-14  7:25   ` RFC crap-patch [PATCH] net: Per CPU separate frag mem accounting Jesper Dangaard Brouer
2013-03-14  8:59     ` Jesper Dangaard Brouer
2013-03-14 20:59       ` Ben Hutchings
2013-03-14 23:12         ` Hannes Frederic Sowa [this message]
2013-03-14 23:39           ` Ben Hutchings
2013-03-15 20:09             ` Hannes Frederic Sowa

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