On Wed, 26 Feb 2020, Matthew Wilcox wrote: > On Wed, Feb 26, 2020 at 09:43:53AM -0800, Yang Shi wrote: > > > No. The pagevec_lookup_entries() calls from mm/truncate.c prefer the > > > new behavior - evicting the head from page cache removes all the tails > > > along with it, so getting the tails a waste of time there too, just as > > > it was in shmem_undo_range(). > > > > TBH I'm not a fun of this hack. This would bring in other confusion or > > complexity. Pagevec is supposed to count in the number of base page, now it > > would treat THP as one page, and there might be mixed base page and THP in > > one pagevec. But, I tend to agree avoiding getting those 14 extra pins at > > the first place might be a better approach. All the complexity are used to > > release those extra pins. > > My long-term goal is to eradicate tail pages entirely, so a pagevec will > end up containing pages of different sizes. If you want to help move > in this direction, I'd be awfully grateful. But I wouldn't say that's > in any way a prerequisite for fixing this current problem. You're right to be moving in that direction, but yes, that is a larger task, and I think both Yang and I have to decline your awful gratitude :) Hugh
