1 files changed, 134 insertions, 32 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 62fe06b..f952f05 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -31,6 +31,33 @@
 #include <asm/pgalloc.h>
 #include "internal.h"
 
+enum scan_result {
+	SCAN_FAIL,
+	SCAN_SUCCEED,
+	SCAN_PMD_NULL,
+	SCAN_EXCEED_NONE_PTE,
+	SCAN_PTE_NON_PRESENT,
+	SCAN_PAGE_RO,
+	SCAN_NO_REFERENCED_PAGE,
+	SCAN_PAGE_NULL,
+	SCAN_SCAN_ABORT,
+	SCAN_PAGE_COUNT,
+	SCAN_PAGE_LRU,
+	SCAN_PAGE_LOCK,
+	SCAN_PAGE_ANON,
+	SCAN_ANY_PROCESS,
+	SCAN_VMA_NULL,
+	SCAN_VMA_CHECK,
+	SCAN_ADDRESS_RANGE,
+	SCAN_SWAP_CACHE_PAGE,
+	SCAN_DEL_PAGE_LRU,
+	SCAN_ALLOC_HUGE_PAGE_FAIL,
+	SCAN_CGROUP_CHARGE_FAIL
+};
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/huge_memory.h>
+
 /*
  * By default transparent hugepage support is disabled in order that avoid
  * to risk increase the memory footprint of applications without a guaranteed
@@ -2198,26 +2225,33 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 					unsigned long address,
 					pte_t *pte)
 {
-	struct page *page;
+	struct page *page = NULL;
 	pte_t *_pte;
-	int none_or_zero = 0;
+	int none_or_zero = 0, result = 0;
 	bool referenced = false, writable = false;
+
 	for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
 	     _pte++, address += PAGE_SIZE) {
 		pte_t pteval = *_pte;
 		if (pte_none(pteval) || (pte_present(pteval) &&
 				is_zero_pfn(pte_pfn(pteval)))) {
 			if (!userfaultfd_armed(vma) &&
-			    ++none_or_zero <= khugepaged_max_ptes_none)
+			    ++none_or_zero <= khugepaged_max_ptes_none) {
 				continue;
-			else
+			} else {
+				result = SCAN_EXCEED_NONE_PTE;
 				goto out;
+			}
 		}
-		if (!pte_present(pteval))
+		if (!pte_present(pteval)) {
+			result = SCAN_PTE_NON_PRESENT;
 			goto out;
+		}
 		page = vm_normal_page(vma, address, pteval);
-		if (unlikely(!page))
+		if (unlikely(!page)) {
+			result = SCAN_PAGE_NULL;
 			goto out;
+		}
 
 		VM_BUG_ON_PAGE(PageCompound(page), page);
 		VM_BUG_ON_PAGE(!PageAnon(page), page);
@@ -2229,8 +2263,10 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		 * is needed to serialize against split_huge_page
 		 * when invoked from the VM.
 		 */
-		if (!trylock_page(page))
+		if (!trylock_page(page)) {
+			result = SCAN_PAGE_LOCK;
 			goto out;
+		}
 
 		/*
 		 * cannot use mapcount: can't collapse if there's a gup pin.
@@ -2239,6 +2275,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		 */
 		if (page_count(page) != 1 + !!PageSwapCache(page)) {
 			unlock_page(page);
+			result = SCAN_PAGE_COUNT;
 			goto out;
 		}
 		if (pte_write(pteval)) {
@@ -2246,6 +2283,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		} else {
 			if (PageSwapCache(page) && !reuse_swap_page(page)) {
 				unlock_page(page);
+				result = SCAN_SWAP_CACHE_PAGE;
 				goto out;
 			}
 			/*
@@ -2260,6 +2298,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		 */
 		if (isolate_lru_page(page)) {
 			unlock_page(page);
+			result = SCAN_DEL_PAGE_LRU;
 			goto out;
 		}
 		/* 0 stands for page_is_file_cache(page) == false */
@@ -2273,10 +2312,21 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced = true;
 	}
-	if (likely(referenced && writable))
-		return 1;
+	if (likely(writable)) {
+		if (likely(referenced)) {
+			result = SCAN_SUCCEED;
+			trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
+							    referenced, writable, result);
+			return 1;
+		}
+	} else {
+		result = SCAN_PAGE_RO;
+	}
+
 out:
 	release_pte_pages(pte, _pte);
+	trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
+					    referenced, writable, result);
 	return 0;
 }
 
@@ -2513,7 +2563,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	pgtable_t pgtable;
 	struct page *new_page;
 	spinlock_t *pmd_ptl, *pte_ptl;
-	int isolated;
+	int isolated, result = 0;
 	unsigned long hstart, hend;
 	struct mem_cgroup *memcg;
 	unsigned long mmun_start;	/* For mmu_notifiers */
@@ -2528,12 +2578,15 @@ static void collapse_huge_page(struct mm_struct *mm,
 
 	/* release the mmap_sem read lock. */
 	new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
-	if (!new_page)
-		return;
+	if (!new_page) {
+		result = SCAN_ALLOC_HUGE_PAGE_FAIL;
+		goto out_nolock;
+	}
 
-	if (unlikely(mem_cgroup_try_charge(new_page, mm,
-					   gfp, &memcg)))
-		return;
+	if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg))) {
+		result = SCAN_CGROUP_CHARGE_FAIL;
+		goto out_nolock;
+	}
 
 	/*
 	 * Prevent all access to pagetables with the exception of
@@ -2541,21 +2594,31 @@ static void collapse_huge_page(struct mm_struct *mm,
 	 * handled by the anon_vma lock + PG_lock.
 	 */
 	down_write(&mm->mmap_sem);
-	if (unlikely(khugepaged_test_exit(mm)))
+	if (unlikely(khugepaged_test_exit(mm))) {
+		result = SCAN_ANY_PROCESS;
 		goto out;
+	}
 
 	vma = find_vma(mm, address);
-	if (!vma)
+	if (!vma) {
+		result = SCAN_VMA_NULL;
 		goto out;
+	}
 	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
 	hend = vma->vm_end & HPAGE_PMD_MASK;
-	if (address < hstart || address + HPAGE_PMD_SIZE > hend)
+	if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
+		result = SCAN_ADDRESS_RANGE;
 		goto out;
-	if (!hugepage_vma_check(vma))
+	}
+	if (!hugepage_vma_check(vma)) {
+		result = SCAN_VMA_CHECK;
 		goto out;
+	}
 	pmd = mm_find_pmd(mm, address);
-	if (!pmd)
+	if (!pmd) {
+		result = SCAN_PMD_NULL;
 		goto out;
+	}
 
 	anon_vma_lock_write(vma->anon_vma);
 
@@ -2592,6 +2655,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 		pmd_populate(mm, pmd, pmd_pgtable(_pmd));
 		spin_unlock(pmd_ptl);
 		anon_vma_unlock_write(vma->anon_vma);
+		result = SCAN_FAIL;
 		goto out;
 	}
 
@@ -2629,10 +2693,15 @@ static void collapse_huge_page(struct mm_struct *mm,
 	*hpage = NULL;
 
 	khugepaged_pages_collapsed++;
+	result = SCAN_SUCCEED;
 out_up_write:
 	up_write(&mm->mmap_sem);
+	trace_mm_collapse_huge_page(mm, isolated, result);
 	return;
 
+out_nolock:
+	trace_mm_collapse_huge_page(mm, isolated, result);
+	return;
 out:
 	mem_cgroup_cancel_charge(new_page, memcg);
 	goto out_up_write;
@@ -2645,8 +2714,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 {
 	pmd_t *pmd;
 	pte_t *pte, *_pte;
-	int ret = 0, none_or_zero = 0;
-	struct page *page;
+	int ret = 0, none_or_zero = 0, result = 0;
+	struct page *page = NULL;
 	unsigned long _address;
 	spinlock_t *ptl;
 	int node = NUMA_NO_NODE;
@@ -2655,8 +2724,10 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
 	pmd = mm_find_pmd(mm, address);
-	if (!pmd)
+	if (!pmd) {
+		result = SCAN_PMD_NULL;
 		goto out;
+	}
 
 	memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
 	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
@@ -2665,19 +2736,25 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 		pte_t pteval = *_pte;
 		if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
 			if (!userfaultfd_armed(vma) &&
-			    ++none_or_zero <= khugepaged_max_ptes_none)
+			    ++none_or_zero <= khugepaged_max_ptes_none) {
 				continue;
-			else
+			} else {
+				result = SCAN_EXCEED_NONE_PTE;
 				goto out_unmap;
+			}
 		}
-		if (!pte_present(pteval))
+		if (!pte_present(pteval)) {
+			result = SCAN_PTE_NON_PRESENT;
 			goto out_unmap;
+		}
 		if (pte_write(pteval))
 			writable = true;
 
 		page = vm_normal_page(vma, _address, pteval);
-		if (unlikely(!page))
+		if (unlikely(!page)) {
+			result = SCAN_PAGE_NULL;
 			goto out_unmap;
+		}
 		/*
 		 * Record which node the original page is from and save this
 		 * information to khugepaged_node_load[].
@@ -2685,26 +2762,49 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 		 * hit record.
 		 */
 		node = page_to_nid(page);
-		if (khugepaged_scan_abort(node))
+		if (khugepaged_scan_abort(node)) {
+			result = SCAN_SCAN_ABORT;
 			goto out_unmap;
+		}
 		khugepaged_node_load[node]++;
 		VM_BUG_ON_PAGE(PageCompound(page), page);
-		if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
+		if (!PageLRU(page)) {
+			result = SCAN_SCAN_ABORT;
+			goto out_unmap;
+		}
+		if (PageLocked(page)) {
+			result = SCAN_PAGE_LOCK;
+			goto out_unmap;
+		}
+		if (!PageAnon(page)) {
+			result = SCAN_PAGE_ANON;
 			goto out_unmap;
+		}
+
 		/*
 		 * cannot use mapcount: can't collapse if there's a gup pin.
 		 * The page must only be referenced by the scanned process
 		 * and page swap cache.
 		 */
-		if (page_count(page) != 1 + !!PageSwapCache(page))
+		if (page_count(page) != 1 + !!PageSwapCache(page)) {
+			result = SCAN_PAGE_COUNT;
 			goto out_unmap;
+		}
 		if (pte_young(pteval) ||
 		    page_is_young(page) || PageReferenced(page) ||
 		    mmu_notifier_test_young(vma->vm_mm, address))
 			referenced = true;
 	}
-	if (referenced && writable)
-		ret = 1;
+	if (writable) {
+		if (referenced) {
+			result = SCAN_SUCCEED;
+			ret = 1;
+		} else {
+			result = SCAN_NO_REFERENCED_PAGE;
+		}
+	} else {
+		result = SCAN_PAGE_RO;
+	}
 out_unmap:
 	pte_unmap_unlock(pte, ptl);
 	if (ret) {
@@ -2713,6 +2813,8 @@ out_unmap:
 		collapse_huge_page(mm, address, hpage, vma, node);
 	}
 out:
+	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
+				     none_or_zero, result);
 	return ret;
 }