Re: [PATCH 3/4] mm: move lazy free pages to inactive list
On 03/10/2015 10:14 PM, Wang, Yalin wrote: >> -Original Message- >> From: Minchan Kim [mailto:minc...@kernel.org] >> Sent: Wednesday, March 11, 2015 9:21 AM >> To: Andrew Morton >> Cc: linux-kernel@vger.kernel.org; linux...@kvack.org; Michal Hocko; >> Johannes Weiner; Mel Gorman; Rik van Riel; Shaohua Li; Wang, Yalin; Minchan >> Kim >> Subject: [PATCH 3/4] mm: move lazy free pages to inactive list >> >> MADV_FREE is hint that it's okay to discard pages if there is >> memory pressure and we uses reclaimers(ie, kswapd and direct reclaim) >> to free them so there is no worth to remain them in active anonymous LRU >> so this patch moves them to inactive LRU list's head. >> >> This means that MADV_FREE-ed pages which were living on the inactive list >> are reclaimed first because they are more likely to be cold rather than >> recently active pages. >> >> A arguable issue for the approach would be whether we should put it to >> head or tail in inactive list. I selected *head* because kernel cannot >> make sure it's really cold or warm for every MADV_FREE usecase but >> at least we know it's not *hot* so landing of inactive head would be >> comprimise for various usecases. >> >> This is fixing a suboptimal behavior of MADV_FREE when pages living on >> the active list will sit there for a long time even under memory >> pressure while the inactive list is reclaimed heavily. This basically >> breaks the whole purpose of using MADV_FREE to help the system to free >> memory which is might not be used. >> >> Acked-by: Michal Hocko >> Signed-off-by: Minchan Kim >> --- >> include/linux/swap.h | 1 + >> mm/madvise.c | 2 ++ >> mm/swap.c| 35 +++ >> 3 files changed, 38 insertions(+) >> >> diff --git a/include/linux/swap.h b/include/linux/swap.h >> index cee108c..0428e4c 100644 >> --- a/include/linux/swap.h >> +++ b/include/linux/swap.h >> @@ -308,6 +308,7 @@ extern void lru_add_drain_cpu(int cpu); >> extern void lru_add_drain_all(void); >> extern void rotate_reclaimable_page(struct page *page); >> extern void deactivate_file_page(struct page *page); >> +extern void deactivate_page(struct page *page); >> extern void swap_setup(void); >> >> extern void add_page_to_unevictable_list(struct page *page); >> diff --git a/mm/madvise.c b/mm/madvise.c >> index ebe692e..22e8f0c 100644 >> --- a/mm/madvise.c >> +++ b/mm/madvise.c >> @@ -340,6 +340,8 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned >> long addr, >> ptent = pte_mkold(ptent); >> ptent = pte_mkclean(ptent); >> set_pte_at(mm, addr, pte, ptent); >> +if (PageActive(page)) >> +deactivate_page(page); >> tlb_remove_tlb_entry(tlb, pte, addr); >> } > > I think this place should be changed like this: > + if (!page_referenced(page, false, NULL, NULL, NULL) && > PageActive(page)) > + deactivate_page(page); > Because we don't know if other processes are reference this page, > If it is true, don't need deactivate this page. We never clear the page and pte referenced bits on an active page, that is only done when the page is moved to the inactive list through LRU movement. In other words, the page_referenced() check will return true most of the time, even if the page was last referenced half an hour ago (but there was no memory pressure). Minchan's code looks correct. The code may even want a ClearPageReferenced(page) in there... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 3/4] mm: move lazy free pages to inactive list
On Mon, Mar 30, 2015 at 10:28:47PM -0700, Andrew Morton wrote: > On Tue, 31 Mar 2015 13:45:25 +0900 Minchan Kim wrote: > > > > > > deactivate_page() doesn't look at or alter PageReferenced(). Should it? > > > > Absolutely true. Thanks. > > Here it goes. > > > > >From 2b2c92eb73a1cceac615b9abd4c0f5f0c3395ff5 Mon Sep 17 00:00:00 2001 > > From: Minchan Kim > > Date: Tue, 31 Mar 2015 13:38:46 +0900 > > Subject: [PATCH] mm: lru_deactivate_fn should clear PG_referenced > > > > deactivate_page aims for accelerate for reclaiming through > > moving pages from active list to inactive list so we should > > clear PG_referenced for the goal. > > > > ... > > > > --- a/mm/swap.c > > +++ b/mm/swap.c > > @@ -800,6 +800,7 @@ static void lru_deactivate_fn(struct page *page, struct > > lruvec *lruvec, > > > > del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE); > > ClearPageActive(page); > > + ClearPageReferenced(page); > > add_page_to_lru_list(page, lruvec, lru); > > > > __count_vm_event(PGDEACTIVATE); > > What if we have > > PageLRU(page) && !PageActive(page) && PageReferenced(page) > > if we really want to "accelerate the reclaim of @page" then we should > clear PG_referenced there too. The function's name is *deactivate*_page. IOW, I think it should work for only pages in active list, IMHO. > > (And what about page_referenced(page) :)) Yes, I considered it when you mentioned PG_referenced. Now, madvise_free clear out access bit of page table when the syscall is called so shrink_page_list could reclaim pages easily. Of course, we could clear access bit by page_referenced for general purpose, not only madvise_free but it would hurt performance for madvise_free so I'd like to leave it unless there is a need for the function. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 3/4] mm: move lazy free pages to inactive list
On Tue, 31 Mar 2015 13:45:25 +0900 Minchan Kim wrote: > > > > deactivate_page() doesn't look at or alter PageReferenced(). Should it? > > Absolutely true. Thanks. > Here it goes. > > >From 2b2c92eb73a1cceac615b9abd4c0f5f0c3395ff5 Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Tue, 31 Mar 2015 13:38:46 +0900 > Subject: [PATCH] mm: lru_deactivate_fn should clear PG_referenced > > deactivate_page aims for accelerate for reclaiming through > moving pages from active list to inactive list so we should > clear PG_referenced for the goal. > > ... > > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -800,6 +800,7 @@ static void lru_deactivate_fn(struct page *page, struct > lruvec *lruvec, > > del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE); > ClearPageActive(page); > + ClearPageReferenced(page); > add_page_to_lru_list(page, lruvec, lru); > > __count_vm_event(PGDEACTIVATE); What if we have PageLRU(page) && !PageActive(page) && PageReferenced(page) if we really want to "accelerate the reclaim of @page" then we should clear PG_referenced there too. (And what about page_referenced(page) :)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 3/4] mm: move lazy free pages to inactive list
Hello Andrew,
On Mon, Mar 30, 2015 at 02:20:10PM -0700, Andrew Morton wrote:
> On Mon, 30 Mar 2015 14:35:02 +0900 Minchan Kim wrote:
>
> > --- a/mm/swap.c
> > +++ b/mm/swap.c
> > @@ -866,6 +866,13 @@ void deactivate_file_page(struct page *page)
> > }
> > }
> >
> > +/**
> > + * deactivate_page - deactivate a page
> > + * @page: page to deactivate
> > + *
> > + * This function moves @page to inactive list if @page was on active list
> > and
> > + * was not unevictable page to accelerate to reclaim @page.
> > + */
> > void deactivate_page(struct page *page)
> > {
> > if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
>
> Thanks.
>
> deactivate_page() doesn't look at or alter PageReferenced(). Should it?
Absolutely true. Thanks.
Here it goes.
>From 2b2c92eb73a1cceac615b9abd4c0f5f0c3395ff5 Mon Sep 17 00:00:00 2001
From: Minchan Kim
Date: Tue, 31 Mar 2015 13:38:46 +0900
Subject: [PATCH] mm: lru_deactivate_fn should clear PG_referenced
deactivate_page aims for accelerate for reclaiming through
moving pages from active list to inactive list so we should
clear PG_referenced for the goal.
Suggested-by: Andrew Morton
Signed-off-by: Minchan Kim
---
mm/swap.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/swap.c b/mm/swap.c
index b65fc8c..6b420022 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -800,6 +800,7 @@ static void lru_deactivate_fn(struct page *page, struct
lruvec *lruvec,
del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE);
ClearPageActive(page);
+ ClearPageReferenced(page);
add_page_to_lru_list(page, lruvec, lru);
__count_vm_event(PGDEACTIVATE);
--
1.9.3
--
Kind regards,
Minchan Kim
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Re: [PATCH 3/4] mm: move lazy free pages to inactive list
On Mon, 30 Mar 2015 14:35:02 +0900 Minchan Kim wrote:
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -866,6 +866,13 @@ void deactivate_file_page(struct page *page)
> }
> }
>
> +/**
> + * deactivate_page - deactivate a page
> + * @page: page to deactivate
> + *
> + * This function moves @page to inactive list if @page was on active list and
> + * was not unevictable page to accelerate to reclaim @page.
> + */
> void deactivate_page(struct page *page)
> {
> if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
Thanks.
deactivate_page() doesn't look at or alter PageReferenced(). Should it?
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Re: [PATCH 3/4] mm: move lazy free pages to inactive list
Hello Andrew,
On Fri, Mar 20, 2015 at 03:43:58PM -0700, Andrew Morton wrote:
> On Wed, 11 Mar 2015 10:20:37 +0900 Minchan Kim wrote:
>
> > MADV_FREE is hint that it's okay to discard pages if there is
> > memory pressure and we uses reclaimers(ie, kswapd and direct reclaim)
> > to free them so there is no worth to remain them in active anonymous LRU
> > so this patch moves them to inactive LRU list's head.
> >
> > This means that MADV_FREE-ed pages which were living on the inactive list
> > are reclaimed first because they are more likely to be cold rather than
> > recently active pages.
> >
> > A arguable issue for the approach would be whether we should put it to
> > head or tail in inactive list. I selected *head* because kernel cannot
> > make sure it's really cold or warm for every MADV_FREE usecase but
> > at least we know it's not *hot* so landing of inactive head would be
> > comprimise for various usecases.
> >
> > This is fixing a suboptimal behavior of MADV_FREE when pages living on
> > the active list will sit there for a long time even under memory
> > pressure while the inactive list is reclaimed heavily. This basically
> > breaks the whole purpose of using MADV_FREE to help the system to free
> > memory which is might not be used.
> >
> > @@ -789,6 +790,23 @@ static void lru_deactivate_file_fn(struct page *page,
> > struct lruvec *lruvec,
> > update_page_reclaim_stat(lruvec, file, 0);
> > }
> >
> > +
> > +static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
> > + void *arg)
> >
> > ...
> >
> > @@ -844,6 +866,18 @@ void deactivate_file_page(struct page *page)
> > }
> > }
> >
> > +void deactivate_page(struct page *page)
> > +{
>
> lru_deactivate_file_fn() and deactivate_file_page() are carefully
> documented and lru_deactivate_fn() and deactivate_page() should
> be as well. In fact it becomes more important now that we have two
> similar-looking things.
Sorry, I have missed this comment.
Acutally, deactive_file_page was too specific on file-backed page
invalidation when I implemented first time. That's why it had a lot
description but deactivate_page is too general so I think short comment
is enough. :)
Here it goes.
Thanks.
>From 1dbff1d18876962e5248346b59e41014561c09ac Mon Sep 17 00:00:00 2001
From: Minchan Kim
Date: Mon, 30 Mar 2015 14:30:44 +0900
Subject: [PATCH] mm: document deactivate_page
This patch adds function description for deactivate_page.
Signed-off-by: Minchan Kim
---
mm/swap.c | 7 +++
1 file changed, 7 insertions(+)
diff --git a/mm/swap.c b/mm/swap.c
index 6b5adc7..b65fc8c 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -866,6 +866,13 @@ void deactivate_file_page(struct page *page)
}
}
+/**
+ * deactivate_page - deactivate a page
+ * @page: page to deactivate
+ *
+ * This function moves @page to inactive list if @page was on active list and
+ * was not unevictable page to accelerate to reclaim @page.
+ */
void deactivate_page(struct page *page)
{
if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
--
1.9.3
>
>
--
Kind regards,
Minchan Kim
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Re: [PATCH 3/4] mm: move lazy free pages to inactive list
On Wed, 11 Mar 2015 10:20:37 +0900 Minchan Kim wrote:
> MADV_FREE is hint that it's okay to discard pages if there is
> memory pressure and we uses reclaimers(ie, kswapd and direct reclaim)
> to free them so there is no worth to remain them in active anonymous LRU
> so this patch moves them to inactive LRU list's head.
>
> This means that MADV_FREE-ed pages which were living on the inactive list
> are reclaimed first because they are more likely to be cold rather than
> recently active pages.
>
> A arguable issue for the approach would be whether we should put it to
> head or tail in inactive list. I selected *head* because kernel cannot
> make sure it's really cold or warm for every MADV_FREE usecase but
> at least we know it's not *hot* so landing of inactive head would be
> comprimise for various usecases.
>
> This is fixing a suboptimal behavior of MADV_FREE when pages living on
> the active list will sit there for a long time even under memory
> pressure while the inactive list is reclaimed heavily. This basically
> breaks the whole purpose of using MADV_FREE to help the system to free
> memory which is might not be used.
>
> @@ -789,6 +790,23 @@ static void lru_deactivate_file_fn(struct page *page,
> struct lruvec *lruvec,
> update_page_reclaim_stat(lruvec, file, 0);
> }
>
> +
> +static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
> + void *arg)
>
> ...
>
> @@ -844,6 +866,18 @@ void deactivate_file_page(struct page *page)
> }
> }
>
> +void deactivate_page(struct page *page)
> +{
lru_deactivate_file_fn() and deactivate_file_page() are carefully
documented and lru_deactivate_fn() and deactivate_page() should
be as well. In fact it becomes more important now that we have two
similar-looking things.
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 3/4] mm: move lazy free pages to inactive list
On Wed, Mar 11, 2015 at 10:14:51AM +0800, Wang, Yalin wrote: > > -Original Message- > > From: Minchan Kim [mailto:minc...@kernel.org] > > Sent: Wednesday, March 11, 2015 9:21 AM > > To: Andrew Morton > > Cc: linux-kernel@vger.kernel.org; linux...@kvack.org; Michal Hocko; > > Johannes Weiner; Mel Gorman; Rik van Riel; Shaohua Li; Wang, Yalin; Minchan > > Kim > > Subject: [PATCH 3/4] mm: move lazy free pages to inactive list > > > > MADV_FREE is hint that it's okay to discard pages if there is > > memory pressure and we uses reclaimers(ie, kswapd and direct reclaim) > > to free them so there is no worth to remain them in active anonymous LRU > > so this patch moves them to inactive LRU list's head. > > > > This means that MADV_FREE-ed pages which were living on the inactive list > > are reclaimed first because they are more likely to be cold rather than > > recently active pages. > > > > A arguable issue for the approach would be whether we should put it to > > head or tail in inactive list. I selected *head* because kernel cannot > > make sure it's really cold or warm for every MADV_FREE usecase but > > at least we know it's not *hot* so landing of inactive head would be > > comprimise for various usecases. > > > > This is fixing a suboptimal behavior of MADV_FREE when pages living on > > the active list will sit there for a long time even under memory > > pressure while the inactive list is reclaimed heavily. This basically > > breaks the whole purpose of using MADV_FREE to help the system to free > > memory which is might not be used. > > > > Acked-by: Michal Hocko > > Signed-off-by: Minchan Kim > > --- > > include/linux/swap.h | 1 + > > mm/madvise.c | 2 ++ > > mm/swap.c| 35 +++ > > 3 files changed, 38 insertions(+) > > > > diff --git a/include/linux/swap.h b/include/linux/swap.h > > index cee108c..0428e4c 100644 > > --- a/include/linux/swap.h > > +++ b/include/linux/swap.h > > @@ -308,6 +308,7 @@ extern void lru_add_drain_cpu(int cpu); > > extern void lru_add_drain_all(void); > > extern void rotate_reclaimable_page(struct page *page); > > extern void deactivate_file_page(struct page *page); > > +extern void deactivate_page(struct page *page); > > extern void swap_setup(void); > > > > extern void add_page_to_unevictable_list(struct page *page); > > diff --git a/mm/madvise.c b/mm/madvise.c > > index ebe692e..22e8f0c 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -340,6 +340,8 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned > > long addr, > > ptent = pte_mkold(ptent); > > ptent = pte_mkclean(ptent); > > set_pte_at(mm, addr, pte, ptent); > > + if (PageActive(page)) > > + deactivate_page(page); > > tlb_remove_tlb_entry(tlb, pte, addr); > > } > > I think this place should be changed like this: > + if (!page_referenced(page, false, NULL, NULL, NULL) && > PageActive(page)) > + deactivate_page(page); > Because we don't know if other processes are reference this page, > If it is true, don't need deactivate this page. The page_referenced is too much heavy operation to do it in madvise_free fast path. If other processes(parent or child) referenced the page, shrink_page_list in slow path could filter it out and activates the page. In addition, shared case for anon pages happens by fork mostly so we could expect child will do exec soonish in many cases. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH 3/4] mm: move lazy free pages to inactive list
> -Original Message- > From: Minchan Kim [mailto:minc...@kernel.org] > Sent: Wednesday, March 11, 2015 9:21 AM > To: Andrew Morton > Cc: linux-kernel@vger.kernel.org; linux...@kvack.org; Michal Hocko; > Johannes Weiner; Mel Gorman; Rik van Riel; Shaohua Li; Wang, Yalin; Minchan > Kim > Subject: [PATCH 3/4] mm: move lazy free pages to inactive list > > MADV_FREE is hint that it's okay to discard pages if there is > memory pressure and we uses reclaimers(ie, kswapd and direct reclaim) > to free them so there is no worth to remain them in active anonymous LRU > so this patch moves them to inactive LRU list's head. > > This means that MADV_FREE-ed pages which were living on the inactive list > are reclaimed first because they are more likely to be cold rather than > recently active pages. > > A arguable issue for the approach would be whether we should put it to > head or tail in inactive list. I selected *head* because kernel cannot > make sure it's really cold or warm for every MADV_FREE usecase but > at least we know it's not *hot* so landing of inactive head would be > comprimise for various usecases. > > This is fixing a suboptimal behavior of MADV_FREE when pages living on > the active list will sit there for a long time even under memory > pressure while the inactive list is reclaimed heavily. This basically > breaks the whole purpose of using MADV_FREE to help the system to free > memory which is might not be used. > > Acked-by: Michal Hocko > Signed-off-by: Minchan Kim > --- > include/linux/swap.h | 1 + > mm/madvise.c | 2 ++ > mm/swap.c| 35 +++ > 3 files changed, 38 insertions(+) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index cee108c..0428e4c 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -308,6 +308,7 @@ extern void lru_add_drain_cpu(int cpu); > extern void lru_add_drain_all(void); > extern void rotate_reclaimable_page(struct page *page); > extern void deactivate_file_page(struct page *page); > +extern void deactivate_page(struct page *page); > extern void swap_setup(void); > > extern void add_page_to_unevictable_list(struct page *page); > diff --git a/mm/madvise.c b/mm/madvise.c > index ebe692e..22e8f0c 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -340,6 +340,8 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned > long addr, > ptent = pte_mkold(ptent); > ptent = pte_mkclean(ptent); > set_pte_at(mm, addr, pte, ptent); > + if (PageActive(page)) > + deactivate_page(page); > tlb_remove_tlb_entry(tlb, pte, addr); > } I think this place should be changed like this: + if (!page_referenced(page, false, NULL, NULL, NULL) && PageActive(page)) + deactivate_page(page); Because we don't know if other processes are reference this page, If it is true, don't need deactivate this page. Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
