From: Alexander Duyck <[email protected]>
Rather than walking over the same pages again and again to get to the pages
that have yet to be reported we can save ourselves a significant amount of
time by simply rotating the list so that when we have a full list of
reported pages the head of the list is pointing to the next non-reported
page. Doing this should save us some significant time when processing each
free list.
This doesn't gain us much in the standard case as all of the non-reported
pages should be near the top of the list already. However in the case of
page shuffling this results in a noticeable improvement. Below are the
will-it-scale page_fault1 w/ THP numbers for 16 tasks with and without
this patch.
Without:
tasks processes processes_idle threads threads_idle
16 8093776.25 0.17 5393242.00 38.20
With:
tasks processes processes_idle threads threads_idle
16 8283274.75 0.17 5594261.00 38.15
Signed-off-by: Alexander Duyck <[email protected]>
---
mm/page_reporting.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index 1047c6872d4f..6885e74c2367 100644
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -131,17 +131,27 @@ void __page_reporting_notify(void)
if (PageReported(page))
continue;
- /* Attempt to pull page from list */
- if (!__isolate_free_page(page, order))
- break;
+ /* Attempt to pull page from list and place in scatterlist */
+ if (*offset) {
+ if (!__isolate_free_page(page, order)) {
+ next = page;
+ break;
+ }
- /* Add page to scatter list */
- --(*offset);
- sg_set_page(&sgl[*offset], page, page_len, 0);
+ /* Add page to scatter list */
+ --(*offset);
+ sg_set_page(&sgl[*offset], page, page_len, 0);
- /* If scatterlist isn't full grab more pages */
- if (*offset)
continue;
+ }
+
+ /*
+ * Make the first non-processed page in the free list
+ * the new head of the free list before we release the
+ * zone lock.
+ */
+ if (&page->lru != list && !list_is_first(&page->lru, list))
+ list_rotate_to_front(&page->lru, list);
/* release lock before waiting on report processing */
spin_unlock_irq(&zone->lock);
@@ -169,6 +179,10 @@ void __page_reporting_notify(void)
break;
}
+ /* Rotate any leftover pages to the head of the freelist */
+ if (&next->lru != list && !list_is_first(&next->lru, list))
+ list_rotate_to_front(&next->lru, list);
+
spin_unlock_irq(&zone->lock);
return err;
On 03.01.20 22:16, Alexander Duyck wrote:
> From: Alexander Duyck <[email protected]>
>
> Rather than walking over the same pages again and again to get to the pages
> that have yet to be reported we can save ourselves a significant amount of
> time by simply rotating the list so that when we have a full list of
> reported pages the head of the list is pointing to the next non-reported
> page. Doing this should save us some significant time when processing each
> free list.
>
> This doesn't gain us much in the standard case as all of the non-reported
> pages should be near the top of the list already. However in the case of
> page shuffling this results in a noticeable improvement. Below are the
> will-it-scale page_fault1 w/ THP numbers for 16 tasks with and without
> this patch.
>
> Without:
> tasks processes processes_idle threads threads_idle
> 16 8093776.25 0.17 5393242.00 38.20
>
> With:
> tasks processes processes_idle threads threads_idle
> 16 8283274.75 0.17 5594261.00 38.15
>
> Signed-off-by: Alexander Duyck <[email protected]>
> ---
> mm/page_reporting.c | 30 ++++++++++++++++++++++--------
> 1 file changed, 22 insertions(+), 8 deletions(-)
Just a minor comment while scanning over the patches (will do more
review soon), you might want to switch to "mm/page_reporting: " styled
subjects for these optimizations.
--
Thanks,
David / dhildenb
On Wed, 2020-01-08 at 14:38 +0100, David Hildenbrand wrote:
> On 03.01.20 22:16, Alexander Duyck wrote:
> > From: Alexander Duyck <[email protected]>
> >
> > Rather than walking over the same pages again and again to get to the pages
> > that have yet to be reported we can save ourselves a significant amount of
> > time by simply rotating the list so that when we have a full list of
> > reported pages the head of the list is pointing to the next non-reported
> > page. Doing this should save us some significant time when processing each
> > free list.
> >
> > This doesn't gain us much in the standard case as all of the non-reported
> > pages should be near the top of the list already. However in the case of
> > page shuffling this results in a noticeable improvement. Below are the
> > will-it-scale page_fault1 w/ THP numbers for 16 tasks with and without
> > this patch.
> >
> > Without:
> > tasks processes processes_idle threads threads_idle
> > 16 8093776.25 0.17 5393242.00 38.20
> >
> > With:
> > tasks processes processes_idle threads threads_idle
> > 16 8283274.75 0.17 5594261.00 38.15
> >
> > Signed-off-by: Alexander Duyck <[email protected]>
> > ---
> > mm/page_reporting.c | 30 ++++++++++++++++++++++--------
> > 1 file changed, 22 insertions(+), 8 deletions(-)
>
> Just a minor comment while scanning over the patches (will do more
> review soon), you might want to switch to "mm/page_reporting: " styled
> subjects for these optimizations.
>
Okay, I will update if needed for the next version.