> -----Original Message----- > From: Michal Miroslaw [mailto:mirq-li...@rere.qmqm.pl] > Sent: Saturday, December 03, 2016 1:45 AM > To: Duyck, Alexander H <alexander.h.du...@intel.com> > Cc: e1000-de...@lists.sf.net; Brandeburg, Jesse <jesse.brandeb...@intel.com> > Subject: Re: [E1000-devel] i40e: Wrong hint on PCIE2.0 system > > On Sat, Dec 03, 2016 at 05:39:08AM +0000, Duyck, Alexander H wrote: > > There is no need for that. This is a Xeon E3-1220, note that there is no > > v2-v? on > the end of it. A quick look-up in ark.intel.com shows it has a gen2 PCIe > connection > with 20 lanes on the CPU itself. > > > > In the case of the comment I would have to agree, another system might be an > option that has to be considered if you are hoping to get a full 40 Gb/s out > of the > part. If however you are only planning to use it for one or maybe two 10 > Gb/s links > you might be okay. That is all that message is really meant to convey. > Basically in > the current configuration you aren't going to be able to get optimal > performance. > > > > Also you should probably be aware that you are going to likely put some > > pretty > serious stress on the memory system for the CPU. I would advise making sure > you > are running DDR1333 and both channels populated as you max out at about 21GB/s > of total memory bandwidth for the CPU. With a 40Gb/s NIC it becomes pretty > easy > to saturate the memory bandwidth on a small processor. > > > > There are other ways to work around the slot/bandwidth problem too. In > > theory > you could probably take a x16 PCIe gen3 capable switch and connect it to the > system. I've seen crazier things. The switch would then negotiate down to > x16 gen2 > on the upstream ports and you could theoretically have x8 gen3 on the > downstream > ports. Then again that would end up eating all but 4 of the 20 available > PCIe lanes > on the CPU and that assumes that a x16 slot is even available for something > other > than PCIe graphics. > > Dear Alex, > > Thanks for your concern. This is a lab box for Q&A, so it's not that a problem > that it has only PCI-e 2.0. > > >> [97789.169918] i40e 0000:01:00.3: PCI-Express: Speed 5.0GT/s Width x8 > >> [97789.169923] i40e 0000:01:00.3: PCI-Express bandwidth available for this > device may be insufficient for optimal performance. > >> [97789.169926] i40e 0000:01:00.3: Please move the device to a different > >> PCI-e > link with more lanes and/or higher transfer rate. > > The thing is - the first line informs what the card got. > The second informs about observed limitation. > But the third is misleading - at least in this setup, and any other where > all the slots are the same. > > Best Regards, > Michał Mirosław >
Hi Michal, Yes, the message is somewhat misleading but there is really nothing that the driver can do to make it more helpful. Generally this issue occurred because people place the device into the wrong slot. In your case, you do not have such a slot. We could change the language a bit to something like "If possible, you may wish to move this device to a different PCI-e link with more lanes and/or higher transfer rate."? But I don't really see how much that gains here. Ultimately the message is meant to convey that you do not have enough bandwidth to run the part at full speed. Thanks, Jake ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today.http://sdm.link/xeonphi _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired
