Re: [PATCH v2 01/13] mm: support madvise(MADV_FREE)

Hi Minchan,

On (11/05/15 08:39), Minchan Kim wrote:
[..]

quoted

I think it makes sense to update pmd_trans_unstable() and
pmd_none_or_trans_huge_or_clear_bad() comments in asm-generic/pgtable.h
Because they explicitly mention MADV_DONTNEED only. Just a thought.

Hmm, When I read comments(but actually I don't understand it 100%), it
says pmd disappearing from MADV_DONTNEED with mmap_sem read-side
lock. But MADV_FREE doesn't remove the pmd. So, I don't understand
what I should add comment. Please suggest if I am missing something.

Hm, sorry, I need to think about it more, probably my comment is irrelevant.
Was fantasizing some stupid use cases like doing MADV_DONTNEED and MADV_FREE
on overlapping addresses from different threads, processes that share mem, etc.

quoted

quoted

@@ -379,6 +502,14 @@ madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 		return madvise_remove(vma, prev, start, end);
 	case MADV_WILLNEED:
 		return madvise_willneed(vma, prev, start, end);
+	case MADV_FREE:
+		/*
+		 * XXX: In this implementation, MADV_FREE works like

		  ^^^^
		XXX

What does it mean?

not much. just a minor note that there is a 'XXX' in "XXX: In this implementation"
comment.

	-ss