On Sun, Nov 13, 2022 at 09:47:12PM +0800, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) wrote: > Hi leon, > > 在 2022/11/12 0:39, Leon Romanovsky 写道: > > On Fri, Nov 11, 2022 at 10:27:18PM +0800, Longpeng(Mike) wrote: > > > From: Longpeng <longpeng2@xxxxxxxxxx> > > > > > > We can enable SRIOV and add VFs by /sys/bus/pci/devices/..../sriov_numvfs, but > > > this operation needs to spend lots of time if there has a large amount of VFs. > > > For example, if the machine has 10 PFs and 250 VFs per-PF, enable all the VFs > > > concurrently would cost about 200-250ms. However most of them are not need to be > > > used at the moment, so we can enable SRIOV first but add VFs on demand. > > > > It is unclear what took 200-250ms, is it physical VF creation or bind of > > the driver to these VFs? > > > It is neither. In our test, we already created physical VFs before, so we > skipped the 100ms waiting when writing PCI_SRIOV_CTRL. And our driver only > probes PF, it just returns an error if the function is VF. It means that you didn't try sriov_drivers_autoprobe. Once it is set to true, It won't even try to probe VFs. > > The hotspot is the sriov_add_vfs (but no driver probe in fact) which is a > long procedure. Each step costs only a little, but the total cost is not > acceptable in some time-sensitive cases. This is also cryptic to me. In standard SR-IOV deployment, all VFs are created and configured while operator booted the machine with sriov_drivers_autoprobe set to false. Once this machine is ready, VFs are assigned to relevant VMs/users through orchestration SW (IMHO, it is supported by all orchestration SW). And only last part (assigning to users) is time-sensitive operation. > > What’s more, the sriov_add_vfs adds the VFs of a PF one by one. So we can > mostly support 10 concurrent calls if there has 10 PFs. I wondered, are you using real HW? or QEMU SR-IOV? What is your server that supports such large number of VFs? BTW, Your change will probably break all SR-IOV devices in the market as they rely on PCI subsystem to have VFs ready and configured. Thanks
