From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Subject: Re: Flow Control and Port Mirroring Revisited Date: Fri, 14 Jan 2011 08:41:36 +0900 Message-ID: <20110113234135.GC8426@verge.net.au> References: <20110106093312.GA1564@verge.net.au> <1294309362.3074.11.camel@edumazet-laptop> <20110106124439.GA17004@verge.net.au> <20110107012356.GA1257@verge.net.au> <20110110093155.GB13420@verge.net.au> <20110113064718.GA17905@verge.net.au> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Eric Dumazet , Rusty Russell , virtualization@lists.linux-foundation.org, dev@openvswitch.org, virtualization@lists.osdl.org, netdev@vger.kernel.org, kvm@vger.kernel.org, "Michael S. Tsirkin" To: Jesse Gross Return-path: Received: from kirsty.vergenet.net ([202.4.237.240]:60379 "EHLO kirsty.vergenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751693Ab1AMXlj (ORCPT ); Thu, 13 Jan 2011 18:41:39 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Jan 13, 2011 at 10:45:38AM -0500, Jesse Gross wrote: > On Thu, Jan 13, 2011 at 1:47 AM, Simon Horman wr= ote: > > On Mon, Jan 10, 2011 at 06:31:55PM +0900, Simon Horman wrote: > >> On Fri, Jan 07, 2011 at 10:23:58AM +0900, Simon Horman wrote: > >> > On Thu, Jan 06, 2011 at 05:38:01PM -0500, Jesse Gross wrote: > >> > > >> > [ snip ] > >> > > > >> > > I know that everyone likes a nice netperf result but I agree w= ith > >> > > Michael that this probably isn't the right question to be aski= ng. =C2=A0I > >> > > don't think that socket buffers are a real solution to the flo= w > >> > > control problem: they happen to provide that functionality but= it's > >> > > more of a side effect than anything. =C2=A0It's just that the = amount of > >> > > memory consumed by packets in the queue(s) doesn't really have= any > >> > > implicit meaning for flow control (think multiple physical ada= pters, > >> > > all with the same speed instead of a virtual device and a phys= ical > >> > > device with wildly different speeds). =C2=A0The analog in the = physical > >> > > world that you're looking for would be Ethernet flow control. > >> > > Obviously, if the question is limiting CPU or memory consumpti= on then > >> > > that's a different story. > >> > > >> > Point taken. I will see if I can control CPU (and thus memory) c= onsumption > >> > using cgroups and/or tc. > >> > >> I have found that I can successfully control the throughput using > >> the following techniques > >> > >> 1) Place a tc egress filter on dummy0 > >> > >> 2) Use ovs-ofctl to add a flow that sends skbs to dummy0 and then = eth1, > >> =C2=A0 =C2=A0this is effectively the same as one of my hacks to th= e datapath > >> =C2=A0 =C2=A0that I mentioned in an earlier mail. The result is th= at eth1 > >> =C2=A0 =C2=A0"paces" the connection. > > > > Further to this, I wonder if there is any interest in providing > > a method to switch the action order - using ovs-ofctl is a hack imh= o - > > and/or switching the default action order for mirroring. >=20 > I'm not sure that there is a way to do this that is correct in the > generic case. It's possible that the destination could be a VM while > packets are being mirrored to a physical device or we could be > multicasting or some other arbitrarily complex scenario. Just think > of what a physical switch would do if it has ports with two different > speeds. Yes, I have considered that case. And I agree that perhaps there is no sensible default. But perhaps we could make it configurable someh= ow?