Hi
> On Wednesday 15 April 2009 00:32:52 Andrea Arcangeli wrote:
> > On Wed, Apr 15, 2009 at 12:26:34AM +1000, Nick Piggin wrote:
> > > Andrea: I didn't veto that set_bit change of yours as such. I just
> >
> > I know you didn't ;)
> >
> > > noted there could be more atomic operations. Actually I would
> > > welcome more comparison between our two approaches, but they seem
> >
> > Agree about the welcome of comparison, it'd be nice to measure it the
> > enterprise workloads that showed the gup_fast gain in the first place.
>
> I think we should be able to ask IBM to run some tests, provided
> they still have machines available to do so. Although I don't want
> to waste their time so we need to have something that has got past
> initial code review and has a chance of being merged.
>
> If we get that far, then I can ask them to run tests definitely.
Oh, it seem very charming idea.
Nick, I hope to help your patch's rollup. It makes good comparision, I think.
Is there my doable thing?
And, I changed my patch.
How about this? I added simple twice check.
because, both do_wp_page and try_to_unmap_one grab ptl. then,
page-fault routine can't change pte while try_to_unmap nuke pte.
---
mm/rmap.c | 30 ++++++++++++++++++++++++------
mm/swapfile.c | 3 ++-
2 files changed, 26 insertions(+), 7 deletions(-)
Index: b/mm/swapfile.c
===================================================================
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -547,7 +547,8 @@ int reuse_swap_page(struct page *page)
SetPageDirty(page);
}
}
- return count == 1;
+
+ return count + page_count(page) == 2;
}
/*
Index: b/mm/rmap.c
===================================================================
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -772,12 +772,18 @@ static int try_to_unmap_one(struct page
if (!pte)
goto out;
- /*
- * If the page is mlock()d, we cannot swap it out.
- * If it's recently referenced (perhaps page_referenced
- * skipped over this mm) then we should reactivate it.
- */
if (!migration) {
+ if (PageSwapCache(page) &&
+ page_count(page) != page_mapcount(page) + 2) {
+ ret = SWAP_FAIL;
+ goto out_unmap;
+ }
+
+ /*
+ * If the page is mlock()d, we cannot swap it out.
+ * If it's recently referenced (perhaps page_referenced
+ * skipped over this mm) then we should reactivate it.
+ */
if (vma->vm_flags & VM_LOCKED) {
ret = SWAP_MLOCK;
goto out_unmap;
@@ -790,7 +796,19 @@ static int try_to_unmap_one(struct page
/* Nuke the page table entry. */
flush_cache_page(vma, address, page_to_pfn(page));
- pteval = ptep_clear_flush_notify(vma, address, pte);
+ pteval = ptep_clear_flush(vma, address, pte);
+
+ if (!migration) {
+ /* re-check */
+ if (PageSwapCache(page) &&
+ page_count(page) != page_mapcount(page) + 2) {
+ /* We lose race against get_user_pages_fast() */
+ set_pte_at(mm, address, pte, pteval);
+ ret = SWAP_FAIL;
+ goto out_unmap;
+ }
+ }
+ mmu_notifier_invalidate_page(vma->vm_mm, address);
/* Move the dirty bit to the physical page now the pte is gone. */
if (pte_dirty(pteval))
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
