On Thu, Sep 26, 2019 at 04:15:49AM +0000, Vamsi Krishna Attunuru wrote: > > > -----Original Message----- > From: dev <dev-boun...@dpdk.org> On Behalf Of Gaëtan Rivet > Sent: Wednesday, September 25, 2019 2:37 PM > To: Slava Ovsiienko <viachesl...@mellanox.com> > Cc: Vamsi Krishna Attunuru <vattun...@marvell.com>; dev@dpdk.org; > ferruh.yi...@intel.com; anatoly.bura...@intel.com; Thomas Monjalon > <tho...@monjalon.net>; Jerin Jacob Kollanukkaran <jer...@marvell.com> > Subject: Re: [dpdk-dev] [PATCH v1 1/1] bus/pci: probe PCI devices in > whitelisted order > > On Wed, Sep 25, 2019 at 06:41:36AM +0000, Slava Ovsiienko wrote: > > > -----Original Message----- > > > From: dev <dev-boun...@dpdk.org> On Behalf Of vattun...@marvell.com > > > Sent: Monday, September 23, 2019 14:57 > > > To: dev@dpdk.org > > > Cc: gaetan.ri...@6wind.com; ferruh.yi...@intel.com; > > > anatoly.bura...@intel.com; Thomas Monjalon <tho...@monjalon.net>; > > > jer...@marvell.com; Vamsi Attunuru <vattun...@marvell.com> > > > Subject: [dpdk-dev] [PATCH v1 1/1] bus/pci: probe PCI devices in > > > whitelisted order > > > > > > From: Vamsi Attunuru <vattun...@marvell.com> > > > > > > Current pci bus driver scans pci devices in the order that it read from > > > sysfs. > > > Accordingly all or whitelisted devices are getting probed. > > > > > > Patch modifies the probing order of whitelisted pci devices in a > > > sequence the devices are whitelisted(using EAL flags). > > > > Thanks, it would be nice to have opportunity to control probing order, > > it might be useful for bonded devices and representors either. > > > > Acked-by: Viacheslav Ovsiienko <viachesl...@mellanox.com> > > > > > > > > It ensures the eth devices that application uses are probed in > > > device whitelisted sequence, in turn it facilitates the packet > > > forwarding applications to work without any packet loss or > > > performance drop when the underneath network ports have different > > > bandwidths. By altering the whitelist order applications like > > > testpmd, l2fwd can forward the ingress traffic to egress port that has of > > > equivalent bandwidth. > > > > > > Signed-off-by: Vamsi Attunuru <vattun...@marvell.com> > > Hello Vamsi, Viacheslav, > > This is a nice patch. I agree that port dependency could be better handled. > The port-mapping part however should be managed at the app level. > > Vamsi, you gave the example of l2fwd and testpmd, being able to properly > configure forwarding directions implicitly. I think the better approach here > is to add these configurations items within the apps directly. Configuring > the mapping at the port level is not precise enough. The proper control is > about cores, port and queues, not only ports. > This patch only solves a limited part of this issue with testpmd. > > I wrote a command to do this, that collided with some stream rework from > Intel at the time (3, 4 years back?), so I did not take the time to force it > through. If there is a need we could discuss about adding this back. I had > needed it to write a PMD, that could be useful to others. > > As you say Viacheslav, there are use-cases that will rely on fine-grained > probe order. However, this patch solves this issue only regarding PCI > devices, depending on other PCI devices. We have in EAL an improper hack > about it, forcing the vdev probe last, because usually ports depending on > others are virtual ones. As this patch shows, the hack is not sufficient, and > as the hack shows, this patch does not cover everything. > > A solution, would be an EAL parameter (I propose --no-dev), that disable > probing for all buses. Applications and devices requiring a fine-grained > probe order, are then free to start in this mode (and maybe force it through > EAL conf), then hotplug ports as they see fit. > > This will keep the existing behavior stable for current apps, while allowing > flexibility for the more advanced ones. > > > Hi Gaetan, > > Thanks, vdev part was not taken care in this patch. Rather than imposing > hotplug for every application which requires port mapping, If vdev probing > order is also handled same as pdevs(in whitelist order), existing > whitelisting feature will serve the port mapping requirement, right. Also the > existing applications get benefited instead of overloading them with more > configuration options. If these probing order is not needed by default, it > can be triggered using an EAL parameter(not added yet). > > Regards, > A Vamsi
Hi, The way buses are written right now, they will each do a whole scan, then they each probe all their devices. You cannot intersperse probes across several buses, i.e. probe a PCI device, then a vdev, then another PCI device. Changing this structure could be difficult. A possible way to do what you want without breaking everything would be to do what the app would have done in my solution above, but from within the EAL: block all probes, then go over a mixed list of (-w) and (--vdev) parameters and hotplug them in order. This would require the --no-dev (or --no-probe, or --no-auto-probe) flag anyway (or as a conf item, or something at least telling the EAL to behave this way). Would this way of doing it work for you? In any case, controlling the probe order should be fixed properly for all buses and the general use-case if possible, instead of limiting the patch to the PCI bus. Kind regards, -- Gaëtan Rivet 6WIND
