On Thu, Oct 19, 2023 at 12:53 PM Peter Xu peterx@redhat.com wrote:
On Thu, Oct 19, 2023 at 05:41:01PM +0200, David Hildenbrand wrote:
That's not my main point. It can easily become a maintenance burden without any real use cases yet that we are willing to support.
That's why I requested a few times that we can discuss the complexity of cross-mm support already here, and I'm all ears if I missed something on the "maintenance burden" part..
I started by listing what I think might be different, and we can easily speedup single-mm with things like "if (ctx->mm != mm)" checks with e.g. memcg, just like what this patch already did with pgtable depositions.
We keep saying "maintenance burden" but we refuse to discuss what is that..
I'll leave that to Suren and Lokesh to decide. For me the worst case is one more flag which might be confusing, which is not the end of the world.. Suren, you may need to work more thoroughly to remove cross-mm implications if so, just like when renaming REMAP to MOVE.
Hi Folks, Sorry, I'm just catching up on all the comments in this thread after a week-long absence. Will be addressing other questions separately but for cross-mm one, I think the best way forward would be for me to split this patch into two with the second one adding cross-mm support. That will clearly show how much additional code that requires and will make it easier for us to decide whether to support it or not. TBH, I don't see the need for an additional flag even if the initial version will be merged without cross-mm support. Once it's added the manpage can mention that starting with a specific Linux version cross-mm is supported, no? Also from my quick read, it sounds like we want to prevent movements of pinned pages regardless of cross-mm support. Is my understanding correct? Thanks, Suren.
Thanks,
-- Peter Xu