On Mon, 28 Nov 2022 15:40:23 -0400 Jason Gunthorpe <j...@nvidia.com> wrote:
> On Mon, Nov 28, 2022 at 11:50:03AM -0700, Alex Williamson wrote: > > > There's a claim here about added complexity that I'm not really seeing. > > It looks like we simply make an ioctl call here and scale our buffer > > based on the minimum of the returned device estimate or our upper > > bound. > > I'm not keen on this, for something like mlx5 that has a small precopy > size and large post-copy size it risks running with an under allocated > buffer, which is harmful to performance. I'm trying to weed out whether there are device assumptions in the implementation, seems like maybe we found one. MIG_DATA_SIZE specifies that it's an estimated data size for stop-copy, so shouldn't that provide the buffer size you're looking for? Thanks, Alex
