Messages in this thread | | | Date | Sun, 13 Nov 2022 21:47:12 +0800 | Subject | Re: [RFC 0/4] pci/sriov: support VFs dynamic addition | From | "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" <> |
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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@huawei.com> >> >> 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.
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.
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.
> If the latter, you can try with sriov_drivers_autoprobe set to true. This is how > ennoblement of large SR-IOV systems is done. > > Also PCI spec declares "VF enable" bit, which is applicable to all VFs > associated to that PF, see section "9.3.3.3.1 VF Enable". > > Thanks > >> >> This series introduces two interfaces: >> 1. sriov_numvfs_no_scan: enable SRIOV without add the VFs. >> 2. sriov_scan_vf_id: add a specific VF. >> >> Longpeng (4): >> pci/sriov: extract sriov_numvfs common helper >> pci/sriov: add vf_bitmap to mark the vf id allocation >> pci/sriov: add sriov_numfs_no_scan interface >> pci/sriov: add sriov_scan_vf_id interface >> >> drivers/pci/iov.c | 162 +++++++++++++++++++++++++++++++++++++++++----- >> drivers/pci/pci.h | 1 + >> 2 files changed, 148 insertions(+), 15 deletions(-) >> >> -- >> 2.23.0 >> > .
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