Hi Minchan,
On Fri, Feb 17, 2017 at 02:45:55PM +0900, Minchan Kim wrote:
> On Thu, Feb 16, 2017 at 04:27:18PM -0800, Shaohua Li wrote:
> > On Thu, Feb 16, 2017 at 01:40:18PM -0500, Johannes Weiner wrote:
> > > On Tue, Feb 14, 2017 at 11:36:09AM -0800, Shaohua Li wrote:
> > > > @@ -1419,11 +1419,18 @@ static int try_to_unmap_one(struct page *page,
> > > > struct vm_area_struct *vma,
> > > > VM_BUG_ON_PAGE(!PageSwapCache(page) &&
> > > > PageSwapBacked(page),
> > > > page);
> > > >
> > > > - if (!PageDirty(page) && (flags & TTU_LZFREE)) {
> > > > - /* It's a freeable page by MADV_FREE */
> > > > - dec_mm_counter(mm, MM_ANONPAGES);
> > > > - rp->lazyfreed++;
> > > > - goto discard;
> > > > + if (flags & TTU_LZFREE) {
> > > > + if (!PageDirty(page)) {
> > > > + /* It's a freeable page by
> > > > MADV_FREE */
> > > > + dec_mm_counter(mm,
> > > > MM_ANONPAGES);
> > > > + rp->lazyfreed++;
> > > > + goto discard;
> > > > + } else {
> > > > + set_pte_at(mm, address,
> > > > pvmw.pte, pteval);
> > > > + ret = SWAP_FAIL;
> > > > +
> > > > page_vma_mapped_walk_done(&pvmw);
> > > > + break;
> > > > + }
> > >
> > > I don't understand why we need the TTU_LZFREE bit in general. More on
> > > that below at the callsite.
> >
> > Sounds useless flag, don't see any reason we shouldn't free the MADV_FREE
> > page
> > in places other than reclaim. Looks TTU_UNMAP is useless too..
>
> Agree on TTU_UNMAP but for example, THP split doesn't mean free lazyfree
> pages,
> I think.
Anon THP splitting uses the migration branch, so we should be fine.
