On Thu, Nov 27, 2014 at 04:49:21PM +0100, Michal Hocko wrote:
> On Mon 20-10-14 19:12:04, Minchan Kim wrote:
> > We don't need to split THP page when MADV_FREE syscall is
> > called. It could be done when VM decide really frees it so
> > we could avoid unnecessary THP split.
> >
> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> > Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
>
> Other than a minor comment below
> Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Thanks!
>
> > ---
> > include/linux/huge_mm.h | 4 ++++
> > mm/huge_memory.c | 35 +++++++++++++++++++++++++++++++++++
> > mm/madvise.c | 21 ++++++++++++++++++++-
> > mm/rmap.c | 8 ++++++--
> > mm/vmscan.c | 28 ++++++++++++++++++----------
> > 5 files changed, 83 insertions(+), 13 deletions(-)
> >
> [...]
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index a21584235bb6..84badee5f46d 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -271,8 +271,26 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> > spinlock_t *ptl;
> > pte_t *pte, ptent;
> > struct page *page;
> > + unsigned long next;
> > +
> > + next = pmd_addr_end(addr, end);
> > + if (pmd_trans_huge(*pmd)) {
> > + if (next - addr != HPAGE_PMD_SIZE) {
> > +#ifdef CONFIG_DEBUG_VM
> > + if (!rwsem_is_locked(&mm->mmap_sem)) {
> > + pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
> > + __func__, addr, end,
> > + vma->vm_start,
> > + vma->vm_end);
> > + BUG();
> > + }
> > +#endif
>
> Why is this code here? madvise_free_pte_range is called only from the
> madvise path and we are holding mmap_sem and relying on that for regular
> pages as well.
Make sense.
>From 2ecc213a2c3634cbee7529055fd6348b03307ed5 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@xxxxxxxxxx>
Date: Mon, 1 Dec 2014 09:07:18 +0900
Subject: [PATCH] mm: remove lock validation check for MADV_FREE
Curretnly, madvise_free_pte_range is called only madvise path
which already holds an mmap_sem so it's pointless to add the
lock validation check.
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
mm/madvise.c | 13 ++-----------
1 file changed, 2 insertions(+), 11 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index dc024effa9bf..6fc9b8298da1 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -275,18 +275,9 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd)) {
- if (next - addr != HPAGE_PMD_SIZE) {
-#ifdef CONFIG_DEBUG_VM
- if (!rwsem_is_locked(&mm->mmap_sem)) {
- pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
- __func__, addr, end,
- vma->vm_start,
- vma->vm_end);
- BUG();
- }
-#endif
+ if (next - addr != HPAGE_PMD_SIZE)
split_huge_page_pmd(vma, addr, pmd);
- } else if (!madvise_free_huge_pmd(tlb, vma, pmd, addr))
+ else if (!madvise_free_huge_pmd(tlb, vma, pmd, addr))
goto next;
/* fall through */
}
--
2.0.0
--
Kind regards,
Minchan Kim
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