On Thu, Jun 16, 2016 at 02:52:52PM +0800, Hillf Danton wrote:
> >
> > From: Ebru Akagunduz <[email protected]>
> >
> > Currently khugepaged makes swapin readahead under down_write. This patch
> > supplies to make swapin readahead under down_read instead of down_write.
> >
> > The patch was tested with a test program that allocates 800MB of memory,
> > writes to it, and then sleeps. The system was forced to swap out all.
> > Afterwards, the test program touches the area by writing, it skips a page
> > in each 20 pages of the area.
> >
> > Link:
> > http://lkml.kernel.org/r/[email protected]
> > Signed-off-by: Ebru Akagunduz <[email protected]>
> > Cc: Hugh Dickins <[email protected]>
> > Cc: Rik van Riel <[email protected]>
> > Cc: "Kirill A. Shutemov" <[email protected]>
> > Cc: Naoya Horiguchi <[email protected]>
> > Cc: Andrea Arcangeli <[email protected]>
> > Cc: Joonsoo Kim <[email protected]>
> > Cc: Cyrill Gorcunov <[email protected]>
> > Cc: Mel Gorman <[email protected]>
> > Cc: David Rientjes <[email protected]>
> > Cc: Vlastimil Babka <[email protected]>
> > Cc: Aneesh Kumar K.V <[email protected]>
> > Cc: Johannes Weiner <[email protected]>
> > Cc: Michal Hocko <[email protected]>
> > Cc: Minchan Kim <[email protected]>
> > Signed-off-by: Andrew Morton <[email protected]>
> > ---
> > mm/huge_memory.c | 92
> > ++++++++++++++++++++++++++++++++++++++------------------
> > 1 file changed, 63 insertions(+), 29 deletions(-)
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index f2bc57c45d2f..96dfe3f09bf6 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2378,6 +2378,35 @@ static bool hugepage_vma_check(struct vm_area_struct
> > *vma)
> > }
> >
> > /*
> > + * If mmap_sem temporarily dropped, revalidate vma
> > + * before taking mmap_sem.
>
> See below
> > @@ -2401,11 +2430,18 @@ static void __collapse_huge_page_swapin(struct
> > mm_struct *mm,
> > continue;
> > swapped_in++;
> > ret = do_swap_page(mm, vma, _address, pte, pmd,
> > -
> > FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT,
> > + FAULT_FLAG_ALLOW_RETRY,
>
> Add a description in change log for it please.
Ebru, would you address it?
> > pteval);
> > + /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
> > + if (ret & VM_FAULT_RETRY) {
> > + down_read(&mm->mmap_sem);
> > + /* vma is no longer available, don't continue to swapin
> > */
> > + if (hugepage_vma_revalidate(mm, vma, address))
> > + return false;
>
> Revalidate vma _after_ acquiring mmap_sem, but the above comment says
> _before_.
Ditto.
> > + if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {
> > + up_read(&mm->mmap_sem);
> > + goto out;
>
> Jump out with mmap_sem released,
>
> > + result = hugepage_vma_revalidate(mm, vma, address);
> > + if (result)
> > + goto out;
>
> but jump out again with mmap_sem held.
>
> They are cleaned up in subsequent darns?
I didn't fold fixups for these
>
--
Kirill A. Shutemov
