On 05/01/2017 02:04 PM, Reza Arbab wrote:
On Mon, May 01, 2017 at 01:41:55PM -0700, John Hubbard wrote:
1. A way to move pages between NUMA nodes, both virtual address and physical
address-based, from kernel mode.
Jérôme's migrate_vma() and migrate_dma() should have this covered, including
DMA-accelerated copy.
Yes, that's good. I wasn't sure from this discussion here if either or both of those
would be used, but now I see.
Are those APIs ready for moving pages between NUMA nodes? As there is no NUMA node
id in the API, are we relying on the pages' membership (using each page and updating
which node it is on)?
5. Something to handle the story of bringing NUMA nodes online and putting them
back offline, given that they require a device driver that may not yet have been
loaded. There are a few minor missing bits there.
This has been prototyped with the driver doing memory hotplug/hotremove. Could you
elaborate a little on what you feel is missing?
We just worked through how to deal with this in our driver, and I remember feeling
worried about the way NUMA nodes can only be put online via a user space action
(through sysfs). It seemed like you'd want to do that from kernel as well, when a
device driver gets loaded.
I was also uneasy about user space trying to bring a node online before the
associated device driver was loaded, and I think it would be nice to be sure that
that whole story is looked at.
The theme here is that driver load/unload is, today, independent from the NUMA node
online/offline, and that's a problem. Not a huge one, though, just worth enumerating
here.
thanks
john h
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