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Commit 0db501f7 authored by Ebru Akagunduz's avatar Ebru Akagunduz Committed by Linus Torvalds
Browse files

mm, thp: convert from optimistic swapin collapsing to conservative 

To detect whether khugepaged swapin is worthwhile, this patch checks the
amount of young pages.  There should be at least half of HPAGE_PMD_NR to
swapin.

Link: http://lkml.kernel.org/r/1468109451-1615-1-git-send-email-ebru.akagunduz@gmail.com


Signed-off-by: default avatarEbru Akagunduz <ebru.akagunduz@gmail.com>
Suggested-by: default avatarMinchan Kim <minchan@kernel.org>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Boaz Harrosh <boaz@plexistor.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 47f863ea

include/trace/events/huge_memory.h

+11 −8
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ 
	EM( SCAN_EXCEED_NONE_PTE,	"exceed_none_pte")		\

	EM( SCAN_PTE_NON_PRESENT,	"pte_non_present")		\

	EM( SCAN_PAGE_RO,		"no_writable_page")		\

	EM( SCAN_NO_REFERENCED_PAGE,	"no_referenced_page")		\

	EM( SCAN_LACK_REFERENCED_PAGE,	"lack_referenced_page")		\

	EM( SCAN_PAGE_NULL,		"page_null")			\

	EM( SCAN_SCAN_ABORT,		"scan_aborted")			\

	EM( SCAN_PAGE_COUNT,		"not_suitable_page_count")	\
@@ -47,7 +47,7 @@ SCAN_STATUS 
TRACE_EVENT(mm_khugepaged_scan_pmd,



	TP_PROTO(struct mm_struct *mm, struct page *page, bool writable,

		 bool referenced, int none_or_zero, int status, int unmapped),

		 int referenced, int none_or_zero, int status, int unmapped),



	TP_ARGS(mm, page, writable, referenced, none_or_zero, status, unmapped),
@@ -55,7 +55,7 @@ TRACE_EVENT(mm_khugepaged_scan_pmd, 
		__field(struct mm_struct *, mm)

		__field(unsigned long, pfn)

		__field(bool, writable)

		__field(bool, referenced)

		__field(int, referenced)

		__field(int, none_or_zero)

		__field(int, status)

		__field(int, unmapped)
@@ -108,14 +108,14 @@ TRACE_EVENT(mm_collapse_huge_page, 
TRACE_EVENT(mm_collapse_huge_page_isolate,



	TP_PROTO(struct page *page, int none_or_zero,

		 bool referenced, bool  writable, int status),

		 int referenced, bool  writable, int status),



	TP_ARGS(page, none_or_zero, referenced, writable, status),



	TP_STRUCT__entry(

		__field(unsigned long, pfn)

		__field(int, none_or_zero)

		__field(bool, referenced)

		__field(int, referenced)

		__field(bool, writable)

		__field(int, status)

	),
@@ -138,25 +138,28 @@ TRACE_EVENT(mm_collapse_huge_page_isolate, 


TRACE_EVENT(mm_collapse_huge_page_swapin,



	TP_PROTO(struct mm_struct *mm, int swapped_in, int ret),

	TP_PROTO(struct mm_struct *mm, int swapped_in, int referenced, int ret),



	TP_ARGS(mm, swapped_in, ret),

	TP_ARGS(mm, swapped_in, referenced, ret),



	TP_STRUCT__entry(

		__field(struct mm_struct *, mm)

		__field(int, swapped_in)

		__field(int, referenced)

		__field(int, ret)

	),



	TP_fast_assign(

		__entry->mm = mm;

		__entry->swapped_in = swapped_in;

		__entry->referenced = referenced;

		__entry->ret = ret;

	),



	TP_printk("mm=%p, swapped_in=%d, ret=%d",

	TP_printk("mm=%p, swapped_in=%d, referenced=%d, ret=%d",

		__entry->mm,

		__entry->swapped_in,

		__entry->referenced,

		__entry->ret)

);

mm/khugepaged.c

+23 −15
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ enum scan_result { 
	SCAN_EXCEED_NONE_PTE,

	SCAN_PTE_NON_PRESENT,

	SCAN_PAGE_RO,

	SCAN_NO_REFERENCED_PAGE,

	SCAN_LACK_REFERENCED_PAGE,

	SCAN_PAGE_NULL,

	SCAN_SCAN_ABORT,

	SCAN_PAGE_COUNT,
@@ -500,8 +500,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 
{

	struct page *page = NULL;

	pte_t *_pte;

	int none_or_zero = 0, result = 0;

	bool referenced = false, writable = false;

	int none_or_zero = 0, result = 0, referenced = 0;

	bool writable = false;



	for (_pte = pte; _pte < pte+HPAGE_PMD_NR;

	     _pte++, address += PAGE_SIZE) {
@@ -580,11 +580,11 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, 
		VM_BUG_ON_PAGE(!PageLocked(page), page);

		VM_BUG_ON_PAGE(PageLRU(page), page);



		/* If there is no mapped pte young don't collapse the page */

		/* There should be enough young pte to collapse the page */

		if (pte_young(pteval) ||

		    page_is_young(page) || PageReferenced(page) ||

		    mmu_notifier_test_young(vma->vm_mm, address))

			referenced = true;

			referenced++;

	}

	if (likely(writable)) {

		if (likely(referenced)) {
@@ -869,7 +869,8 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address) 


static bool __collapse_huge_page_swapin(struct mm_struct *mm,

					struct vm_area_struct *vma,

					unsigned long address, pmd_t *pmd)

					unsigned long address, pmd_t *pmd,

					int referenced)

{

	pte_t pteval;

	int swapped_in = 0, ret = 0;
@@ -887,12 +888,19 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, 
		if (!is_swap_pte(pteval))

			continue;

		swapped_in++;

		/* we only decide to swapin, if there is enough young ptes */

		if (referenced < HPAGE_PMD_NR/2) {

			trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

			return false;

		}

		ret = do_swap_page(&fe, pteval);



		/* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */

		if (ret & VM_FAULT_RETRY) {

			down_read(&mm->mmap_sem);

			if (hugepage_vma_revalidate(mm, address)) {

				/* vma is no longer available, don't continue to swapin */

				trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

				return false;

			}

			/* check if the pmd is still valid */
@@ -900,7 +908,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, 
				return false;

		}

		if (ret & VM_FAULT_ERROR) {

			trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);

			trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);

			return false;

		}

		/* pte is unmapped now, we need to map it */
@@ -908,7 +916,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm, 
	}

	fe.pte--;

	pte_unmap(fe.pte);

	trace_mm_collapse_huge_page_swapin(mm, swapped_in, 1);

	trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);

	return true;

}
@@ -916,7 +924,7 @@ static void collapse_huge_page(struct mm_struct *mm, 
				   unsigned long address,

				   struct page **hpage,

				   struct vm_area_struct *vma,

				   int node)

				   int node, int referenced)

{

	pmd_t *pmd, _pmd;

	pte_t *pte;
@@ -973,7 +981,7 @@ static void collapse_huge_page(struct mm_struct *mm, 
	 * If it fails, we release mmap_sem and jump out_nolock.

	 * Continuing to collapse causes inconsistency.

	 */

	if (!__collapse_huge_page_swapin(mm, vma, address, pmd)) {

	if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {

		mem_cgroup_cancel_charge(new_page, memcg, true);

		up_read(&mm->mmap_sem);

		goto out_nolock;
@@ -1084,12 +1092,12 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, 
{

	pmd_t *pmd;

	pte_t *pte, *_pte;

	int ret = 0, none_or_zero = 0, result = 0;

	int ret = 0, none_or_zero = 0, result = 0, referenced = 0;

	struct page *page = NULL;

	unsigned long _address;

	spinlock_t *ptl;

	int node = NUMA_NO_NODE, unmapped = 0;

	bool writable = false, referenced = false;

	bool writable = false;



	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
@@ -1177,14 +1185,14 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, 
		if (pte_young(pteval) ||

		    page_is_young(page) || PageReferenced(page) ||

		    mmu_notifier_test_young(vma->vm_mm, address))

			referenced = true;

			referenced++;

	}

	if (writable) {

		if (referenced) {

			result = SCAN_SUCCEED;

			ret = 1;

		} else {

			result = SCAN_NO_REFERENCED_PAGE;

			result = SCAN_LACK_REFERENCED_PAGE;

		}

	} else {

		result = SCAN_PAGE_RO;
@@ -1194,7 +1202,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, 
	if (ret) {

		node = khugepaged_find_target_node();

		/* collapse_huge_page will return with the mmap_sem released */

		collapse_huge_page(mm, address, hpage, vma, node);

		collapse_huge_page(mm, address, hpage, vma, node, referenced);

	}

out:

	trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,