On Wed, Jan 27, 2021 at 03:36:41PM -0800, Mike Kravetz wrote: > Yes, this patch is somewhat optional. It should be a minor improvement > in cases where we are dealing with hpages in a non-migratable hstate. > Although, I do not believe this is the common case. > > The real reason for even looking into this was a comment by Oscar. With > the name change to HPageMigratable, it implies that the page is migratable. > However, this is not the case if the page's hstate does not support migration. > So, if we check the hstate when setting the flag we can eliminate those > cases where the page is certainly not migratable. > > I don't really love this patch. It has minimal functional value. > > Oscar, what do you think about dropping this? Yeah, I remember this topic arose during a discussion of patch#2 in the early versions, about whether the renaming to HPageMigratable made sense. Back then I thought that we could have this in one place at fault-path [1], which should have made this prettier, but it is not the case. True is that the optimization is little, so I am fine with dropping this patch. unmap_and_move_huge_page() fences off pages belonging to non-migratable hstates. [1] https://patchwork.kernel.org/project/linux-mm/patch/20210120013049.311822-3-mike.kravetz@xxxxxxxxxx/#23914033 Thanks -- Oscar Salvador SUSE L3
