Re: [PATCH RFC v2 4/4] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

On Tue, 7 Nov 2017, Vlastimil Babka wrote:

quoted

Migrate pages moves the pages of a single process there is no TARGET
process.

migrate_pages(2) takes a pid argument

"migrate_pages()  attempts  to  move all pages of the process pid that
are in memory nodes old_nodes to the memory nodes in new_nodes. "

Ok missed that. Most use cases here are on the current process.

Fundamentally a process can have shared pages outside of the cpuset that
a process is restricted to. Thus I would think that migration to any of
the allowed nodes of the current process that is calling migrate pages
is ok. The caller wants this and the caller has a right to allocate on
these nodes. It would be strange if migrate_pages would allow allocation
outside of the current cpuset.

quoted

Thus thehe *target* nodes need to be a subset of the current cpu set.

And therefore the above still holds.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>