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[PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged

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  [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged Ebru Akagunduz <ebru.akagunduz@gmail.com> - 2016-04-07 19:30 +0200
    Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged Rik van Riel <riel@redhat.com> - 2016-04-07 19:40 +0200
    Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged kbuild test robot <lkp@intel.com> - 2016-04-07 19:50 +0200
    Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged Cyrill Gorcunov <gorcunov@gmail.com> - 2016-04-07 21:00 +0200
      Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged Rik van Riel <riel@redhat.com> - 2016-04-07 21:40 +0200
        Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged Cyrill Gorcunov <gorcunov@gmail.com> - 2016-04-07 21:50 +0200
          Re: [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged Ebru Akagunduz <ebru.akagunduz@gmail.com> - 2016-04-07 22:20 +0200

#1373588 — [PATCH v5 2/2] mm, thp: avoid unnecessary swapin in khugepaged

Currently khugepaged makes swapin readahead to improve
THP collapse rate. This patch checks vm statistics
to avoid workload of swapin, if unnecessary. So that
when system under pressure, khugepaged won't consume
resources to swapin and won't trigger direct reclaim
when swapin readahead.

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. When waiting to swapin readahead
left part of the test, the memory forced to be busy
doing page reclaim. There was enough free memory during
test, khugepaged did not swapin readahead due to business.

Test results:

                        After swapped out
-------------------------------------------------------------------
              | Anonymous | AnonHugePages | Swap      | Fraction  |
-------------------------------------------------------------------
With patch    | 0 kB      |  0 kB         | 800000 kB |    %100   |
-------------------------------------------------------------------
Without patch | 0 kB      |  0 kB         | 800000 kB |    %100   |
-------------------------------------------------------------------

                        After swapped in
-------------------------------------------------------------------
              | Anonymous | AnonHugePages | Swap      | Fraction  |
-------------------------------------------------------------------
With patch    | 384812 kB | 96256 kB      | 415188 kB |    %25    |
-------------------------------------------------------------------
Without patch | 389728 kB | 194560 kB     | 410272 kB |    %49    |
-------------------------------------------------------------------

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
---
Changes in v2:
 - Add reference to specify which patch fixed (Ebru Akagunduz)
 - Fix commit subject line (Ebru Akagunduz)

Changes in v3:
 - Remove default values of allocstall (Kirill A. Shutemov)

Changes in v4:
 - define unsigned long allocstall instead of unsigned long int
   (Vlastimil Babka)
 - compare allocstall when khugepaged goes to sleep
   (Rik van Riel, Vlastimil Babka)

Changes in v5:
 - Drop fixes sha part because fixed patch is not in Linus's tree
   (Michal Hocko)
 - Save allocstall where khugepaged exactly sleeps (Michal Hocko)


Note: I didn't add optimistic swapin and mmap_sem in this
      patch series. I couldn't overcome yet.
      I'll send them after the series ends up.

 mm/huge_memory.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8202141..e7d905c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -102,6 +102,7 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
  */
 static unsigned int khugepaged_max_ptes_none __read_mostly;
 static unsigned int khugepaged_max_ptes_swap __read_mostly = HPAGE_PMD_NR/8;
+static unsigned long allocstall;
 
 static int khugepaged(void *none);
 static int khugepaged_slab_init(void);
@@ -2437,7 +2438,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	struct page *new_page;
 	spinlock_t *pmd_ptl, *pte_ptl;
 	int isolated = 0, result = 0;
-	unsigned long hstart, hend;
+	unsigned long hstart, hend, swap, curr_allocstall;
 	struct mem_cgroup *memcg;
 	unsigned long mmun_start;	/* For mmu_notifiers */
 	unsigned long mmun_end;		/* For mmu_notifiers */
@@ -2492,7 +2493,14 @@ static void collapse_huge_page(struct mm_struct *mm,
 		goto out;
 	}
 
-	__collapse_huge_page_swapin(mm, vma, address, pmd);
+	swap = get_mm_counter(mm, MM_SWAPENTS);
+	curr_allocstall = sum_vm_event(ALLOCSTALL);
+	/*
+	 * When system under pressure, don't swapin readahead.
+	 * So that avoid unnecessary resource consuming.
+	 */
+	if (allocstall == curr_allocstall && swap !=)
+		__collapse_huge_page_swapin(mm, vma, address, pmd);
 
 	anon_vma_lock_write(vma->anon_vma);
 
@@ -2886,14 +2894,17 @@ static void khugepaged_wait_work(void)
 		if (!khugepaged_scan_sleep_millisecs)
 			return;
 
+		allocstall = sum_vm_event(ALLOCSTALL);
 		wait_event_freezable_timeout(khugepaged_wait,
 					     kthread_should_stop(),
 			msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
 		return;
 	}
 
-	if (khugepaged_enabled())
+	if (khugepaged_enabled()) {
+		allocstall = sum_vm_event(ALLOCSTALL);
 		wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
+	}
 }
 
 static int khugepaged(void *none)
@@ -2902,6 +2913,7 @@ static int khugepaged(void *none)
 
 	set_freezable();
 	set_user_nice(current, MAX_NICE);
+	allocstall = sum_vm_event(ALLOCSTALL);
 
 	while (!kthread_should_stop()) {
 		khugepaged_do_scan();
-- 
1.9.1

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#1373593

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On Thu, 2016-04-07 at 20:28 +0300, Ebru Akagunduz wrote:
> Currently khugepaged makes swapin readahead to improve
> THP collapse rate. This patch checks vm statistics
> to avoid workload of swapin, if unnecessary. So that
> when system under pressure, khugepaged won't consume
> resources to swapin and won't trigger direct reclaim
> when swapin readahead.
> 
> 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. When waiting to swapin readahead
> left part of the test, the memory forced to be busy
> doing page reclaim. There was enough free memory during
> test, khugepaged did not swapin readahead due to business.
> 
> Test results:
> 
>                         After swapped out
> -------------------------------------------------------------------
>               | Anonymous | AnonHugePages | Swap      | Fraction  |
> -------------------------------------------------------------------
> With patch    | 0 kB      |  0 kB         | 800000 kB |    %100   |
> -------------------------------------------------------------------
> Without patch | 0 kB      |  0 kB         | 800000 kB |    %100   |
> -------------------------------------------------------------------
> 
>                         After swapped in
> -------------------------------------------------------------------
>               | Anonymous | AnonHugePages | Swap      | Fraction  |
> -------------------------------------------------------------------
> With patch    | 384812 kB | 96256 kB      | 415188 kB |    %25    |
> -------------------------------------------------------------------
> Without patch | 389728 kB | 194560 kB     | 410272 kB |    %49    |
> -------------------------------------------------------------------
> 
> Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>

Acked-by: Rik van Riel <riel@redhat.com>

-- 
All Rights Reversed.

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#1373603

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Hi Ebru,

[auto build test ERROR on next-20160407]
[cannot apply to v4.6-rc2 v4.6-rc1 v4.5-rc7 v4.6-rc2]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Ebru-Akagunduz/mm-thp-Fix-unnecessarry-resource-consuming-in-swapin/20160408-013104
config: x86_64-randconfig-x000-201614 (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   mm/huge_memory.c: In function 'collapse_huge_page':
>> mm/huge_memory.c:2516:46: error: expected expression before ')' token
     if (allocstall == curr_allocstall && swap !=)
                                                 ^

vim +2516 mm/huge_memory.c

  2510		swap = get_mm_counter(mm, MM_SWAPENTS);
  2511		curr_allocstall = sum_vm_event(ALLOCSTALL);
  2512		/*
  2513		 * When system under pressure, don't swapin readahead.
  2514		 * So that avoid unnecessary resource consuming.
  2515		 */
> 2516		if (allocstall == curr_allocstall && swap !=)
  2517			__collapse_huge_page_swapin(mm, vma, address, pmd);
  2518	
  2519		anon_vma_lock_write(vma->anon_vma);

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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#1373657

On Thu, Apr 07, 2016 at 08:28:01PM +0300, Ebru Akagunduz wrote:
...
> +	swap = get_mm_counter(mm, MM_SWAPENTS);
> +	curr_allocstall = sum_vm_event(ALLOCSTALL);
> +	/*
> +	 * When system under pressure, don't swapin readahead.
> +	 * So that avoid unnecessary resource consuming.
> +	 */
> +	if (allocstall == curr_allocstall && swap !=)
> +		__collapse_huge_page_swapin(mm, vma, address, pmd);

This !=) looks like someone got fun ;)

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#1373705

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On Thu, 2016-04-07 at 21:58 +0300, Cyrill Gorcunov wrote:
> On Thu, Apr 07, 2016 at 08:28:01PM +0300, Ebru Akagunduz wrote:
> ...
> > 
> > +	swap = get_mm_counter(mm, MM_SWAPENTS);
> > +	curr_allocstall = sum_vm_event(ALLOCSTALL);
> > +	/*
> > +	 * When system under pressure, don't swapin readahead.
> > +	 * So that avoid unnecessary resource consuming.
> > +	 */
> > +	if (allocstall == curr_allocstall && swap !=)
> > +		__collapse_huge_page_swapin(mm, vma, address,
> > pmd);
> This !=) looks like someone got fun ;)

Looks like someone sent out emails before refreshing the
patch, which is a such an easy mistake to make I must have
done it a dozen times by now :)

-- 
All Rights Reversed.

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#1373706

On Thu, Apr 07, 2016 at 03:39:05PM -0400, Rik van Riel wrote:
> > This !=) looks like someone got fun ;)
> 
> Looks like someone sent out emails before refreshing the
> patch, which is a such an easy mistake to make I must have
> done it a dozen times by now :)

I've been there many times as well :)

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#1373717

On Thu, Apr 07, 2016 at 10:47:59PM +0300, Cyrill Gorcunov wrote:
> On Thu, Apr 07, 2016 at 03:39:05PM -0400, Rik van Riel wrote:
> > > This !=) looks like someone got fun ;)
> > 
> > Looks like someone sent out emails before refreshing the
> > patch, which is a such an easy mistake to make I must have
> > done it a dozen times by now :)
> 
> I've been there many times as well :)

I apologize for inconvenience. When making
last checks on this patch, this happened and
I wasn't aware of it. I'll fix this, test and
send in next version.

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