[lkml]   [2018]   [Mar]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 10/10] nvmet: Optionally use PCI P2P memory
> > Ideally, we'd want to use an NVME CMB buffer as p2p memory. This would
> > save an extra PCI transfer as the NVME card could just take the data
> > out of it's own memory. However, at this time, cards with CMB buffers
> > don't seem to be available.

> Can you describe what would be the plan to have it when these devices
> do come along? I'd say that p2p_dev needs to become a nvmet_ns reference
> and not from nvmet_ctrl. Then, when cmb capable devices come along, the
> ns can prefer to use its own cmb instead of locating a p2p_dev device?

Hi Sagi

Thanks for the review! That commit message is somewhat dated as NVMe controllers with CMBs that support RDS and WDS are now commercially available [1]. However we have not yet tried to do any kind of optimization around this yet in terms of determining which p2p_dev to use. Your suggest above looks good and we can look into this kind of optimization in due course.


>> + ctrl->p2p_dev = pci_p2pmem_find(&ctrl->p2p_clients);

> This is the first p2p_dev found right? What happens if I have more than
> a single p2p device? In theory I'd have more p2p memory I can use. Have
> you considered making pci_p2pmem_find return the least used suitable
> device?

Yes pci_p2pmem_find will always return the first valid p2p_dev found. At the very least we should update this allocate over all the valid p2p_dev. Since the load on any given p2p_dev will vary over time I think a random allocation of the devices makes sense (at least for now).


 \ /
  Last update: 2018-03-01 17:16    [W:0.173 / U:1.548 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site