From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Gross Subject: Re: Flow Control and Port Mirroring Revisited Date: Thu, 13 Jan 2011 10:45:38 -0500 Message-ID: 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=ISO-8859-1 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: Simon Horman Return-path: In-Reply-To: <20110113064718.GA17905@verge.net.au> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Jan 13, 2011 at 1:47 AM, Simon Horman wrot= e: > 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 wit= h >> > > Michael that this probably isn't the right question to be asking= =2E =A0I >> > > don't think that socket buffers are a real solution to the flow >> > > control problem: they happen to provide that functionality but i= t's >> > > more of a side effect than anything. =A0It's just that the amoun= t of >> > > memory consumed by packets in the queue(s) doesn't really have a= ny >> > > implicit meaning for flow control (think multiple physical adapt= ers, >> > > all with the same speed instead of a virtual device and a physic= al >> > > device with wildly different speeds). =A0The analog in the physi= cal >> > > world that you're looking for would be Ethernet flow control. >> > > Obviously, if the question is limiting CPU or memory consumption= then >> > > that's a different story. >> > >> > Point taken. I will see if I can control CPU (and thus memory) con= sumption >> > 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 et= h1, >> =A0 =A0this is effectively the same as one of my hacks to the datapa= th >> =A0 =A0that I mentioned in an earlier mail. The result is that eth1 >> =A0 =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 imho = - > and/or switching the default action order for mirroring. 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.