On Tue, May 28, 2019 at 08:15:23PM +0800, Hillf Danton wrote:
< snip >
> > > > +
> > > > + get_page(page);
> > > > + spin_unlock(ptl);
> > > > + lock_page(page);
> > > > + err = split_huge_page(page);
> > > > + unlock_page(page);
> > > > + put_page(page);
> > > > + if (!err)
> > > > + goto regular_page;
> > > > + return 0;
> > > > + }
> > > > +
> > > > + pmdp_test_and_clear_young(vma, addr, pmd);
> > > > + deactivate_page(page);
> > > > +huge_unlock:
> > > > + spin_unlock(ptl);
> > > > + return 0;
> > > > + }
> > > > +
> > > > + if (pmd_trans_unstable(pmd))
> > > > + return 0;
> > > > +
> > > > +regular_page:
> > >
> > > Take a look at pending signal?
> >
> > Do you have any reason to see pending signal here? I want to know what's
> > your requirement so that what's the better place to handle it.
> >
> We could bail out without work done IMO if there is a fatal siganl pending.
> And we can do that, if it makes sense to you, before the hard work.
Make sense, especically, swapping out.
I will add it in next revision.
>
> > >
> > > > + orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> > > > + for (pte = orig_pte; addr < end; pte++, addr += PAGE_SIZE) {
> > >
> > > s/end/next/ ?
> >
> > Why do you think it should be next?
> >
> Simply based on the following line, and afraid that next != end
> > > > + next = pmd_addr_end(addr, end);
pmd_addr_end will return smaller address so end is more proper.
>
> > > > + ptent = *pte;
> > > > +
> > > > + if (pte_none(ptent))
> > > > + continue;
> > > > +
> > > > + if (!pte_present(ptent))
> > > > + continue;
> > > > +
> > > > + page = vm_normal_page(vma, addr, ptent);
> > > > + if (!page)
> > > > + continue;
> > > > +
> > > > + if (page_mapcount(page) > 1)
> > > > + continue;
> > > > +
> > > > + ptep_test_and_clear_young(vma, addr, pte);
> > > > + deactivate_page(page);
> > > > + }
> > > > +
> > > > + pte_unmap_unlock(orig_pte, ptl);
> > > > + cond_resched();
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +static long madvise_cool(struct vm_area_struct *vma,
> > > > + unsigned long start_addr, unsigned long end_addr)
> > > > +{
> > > > + struct mm_struct *mm = vma->vm_mm;
> > > > + struct mmu_gather tlb;
> > > > +
> > > > + if (vma->vm_flags & (VM_LOCKED|VM_HUGETLB|VM_PFNMAP))
> > > > + return -EINVAL;
> > >
> > > No service in case of VM_IO?
> >
> > I don't know VM_IO would have regular LRU pages but just follow normal
> > convention for DONTNEED and FREE.
> > Do you have anything in your mind?
> >
> I want to skip a mapping set up for DMA.
What you meant is those pages in VM_IO vma are not in LRU list?
Or
pages in the vma are always pinned so no worth to deactivate or reclaim?
