[RFC v2 4/5] khugepaged: add defer option to mTHP options

[Nico Pache <npache@redhat.com>]

Now that we have defer to globally disable THPs at fault time, lets add
a defer setting to the mTHP options. This will allow khugepaged to
operate at that order, while avoiding it at PF time.

Signed-off-by: Nico Pache <npache@redhat.com>
---
 include/linux/huge_mm.h |  5 +++++
 mm/huge_memory.c        | 38 +++++++++++++++++++++++++++++++++-----
 mm/khugepaged.c         | 10 +++++-----
 3 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index fb381ca720ea..8173a9ab0f3b 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -92,6 +92,7 @@ extern struct kobj_attribute thpsize_shmem_enabled_attr;
 #define TVA_SMAPS		(1 << 0)	/* Will be used for procfs */
 #define TVA_IN_PF		(1 << 1)	/* Page fault handler */
 #define TVA_ENFORCE_SYSFS	(1 << 2)	/* Obey sysfs configuration */
+#define TVA_IN_KHUGEPAGE	((1 << 2) | (1 << 3)) /* Khugepaged defer support */
 
 #define thp_vma_allowable_order(vma, vm_flags, tva_flags, order) \
 	(!!thp_vma_allowable_orders(vma, vm_flags, tva_flags, BIT(order)))
@@ -173,6 +174,7 @@ extern unsigned long transparent_hugepage_flags;
 extern unsigned long huge_anon_orders_always;
 extern unsigned long huge_anon_orders_madvise;
 extern unsigned long huge_anon_orders_inherit;
+extern unsigned long huge_anon_orders_defer;
 
 static inline bool hugepage_global_enabled(void)
 {
@@ -297,6 +299,9 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
 	/* Optimization to check if required orders are enabled early. */
 	if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) {
 		unsigned long mask = READ_ONCE(huge_anon_orders_always);
+
+		if ((tva_flags) & (TVA_IN_KHUGEPAGE))
+			mask |= READ_ONCE(huge_anon_orders_defer);
 		if (vm_flags & VM_HUGEPAGE)
 			mask |= READ_ONCE(huge_anon_orders_madvise);
 		if (hugepage_global_always() || hugepage_global_defer() ||
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a5e66a12bae8..de45595b0f98 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -81,6 +81,7 @@ unsigned long huge_zero_pfn __read_mostly = ~0UL;
 unsigned long huge_anon_orders_always __read_mostly;
 unsigned long huge_anon_orders_madvise __read_mostly;
 unsigned long huge_anon_orders_inherit __read_mostly;
+unsigned long huge_anon_orders_defer __read_mostly;
 static bool anon_orders_configured __initdata;
 
 static inline bool file_thp_enabled(struct vm_area_struct *vma)
@@ -505,13 +506,15 @@ static ssize_t anon_enabled_show(struct kobject *kobj,
 	const char *output;
 
 	if (test_bit(order, &huge_anon_orders_always))
-		output = "[always] inherit madvise never";
+		output = "[always] inherit madvise defer never";
 	else if (test_bit(order, &huge_anon_orders_inherit))
-		output = "always [inherit] madvise never";
+		output = "always [inherit] madvise defer never";
 	else if (test_bit(order, &huge_anon_orders_madvise))
-		output = "always inherit [madvise] never";
+		output = "always inherit [madvise] defer never";
+	else if (test_bit(order, &huge_anon_orders_defer))
+		output = "always inherit madvise [defer] never";
 	else
-		output = "always inherit madvise [never]";
+		output = "always inherit madvise defer [never]";
 
 	return sysfs_emit(buf, "%s\n", output);
 }
@@ -527,25 +530,36 @@ static ssize_t anon_enabled_store(struct kobject *kobj,
 		spin_lock(&huge_anon_orders_lock);
 		clear_bit(order, &huge_anon_orders_inherit);
 		clear_bit(order, &huge_anon_orders_madvise);
+		clear_bit(order, &huge_anon_orders_defer);
 		set_bit(order, &huge_anon_orders_always);
 		spin_unlock(&huge_anon_orders_lock);
 	} else if (sysfs_streq(buf, "inherit")) {
 		spin_lock(&huge_anon_orders_lock);
 		clear_bit(order, &huge_anon_orders_always);
 		clear_bit(order, &huge_anon_orders_madvise);
+		clear_bit(order, &huge_anon_orders_defer);
 		set_bit(order, &huge_anon_orders_inherit);
 		spin_unlock(&huge_anon_orders_lock);
 	} else if (sysfs_streq(buf, "madvise")) {
 		spin_lock(&huge_anon_orders_lock);
 		clear_bit(order, &huge_anon_orders_always);
 		clear_bit(order, &huge_anon_orders_inherit);
+		clear_bit(order, &huge_anon_orders_defer);
 		set_bit(order, &huge_anon_orders_madvise);
 		spin_unlock(&huge_anon_orders_lock);
+	} else if (sysfs_streq(buf, "defer")) {
+		spin_lock(&huge_anon_orders_lock);
+		clear_bit(order, &huge_anon_orders_always);
+		clear_bit(order, &huge_anon_orders_inherit);
+		clear_bit(order, &huge_anon_orders_madvise);
+		set_bit(order, &huge_anon_orders_defer);
+		spin_unlock(&huge_anon_orders_lock);
 	} else if (sysfs_streq(buf, "never")) {
 		spin_lock(&huge_anon_orders_lock);
 		clear_bit(order, &huge_anon_orders_always);
 		clear_bit(order, &huge_anon_orders_inherit);
 		clear_bit(order, &huge_anon_orders_madvise);
+		clear_bit(order, &huge_anon_orders_defer);
 		spin_unlock(&huge_anon_orders_lock);
 	} else
 		ret = -EINVAL;
@@ -991,7 +1005,7 @@ static char str_dup[PAGE_SIZE] __initdata;
 static int __init setup_thp_anon(char *str)
 {
 	char *token, *range, *policy, *subtoken;
-	unsigned long always, inherit, madvise;
+	unsigned long always, inherit, madvise, defer;
 	char *start_size, *end_size;
 	int start, end, nr;
 	char *p;
@@ -1003,6 +1017,8 @@ static int __init setup_thp_anon(char *str)
 	always = huge_anon_orders_always;
 	madvise = huge_anon_orders_madvise;
 	inherit = huge_anon_orders_inherit;
+	defer = huge_anon_orders_defer;
+
 	p = str_dup;
 	while ((token = strsep(&p, ";")) != NULL) {
 		range = strsep(&token, ":");
@@ -1042,18 +1058,28 @@ static int __init setup_thp_anon(char *str)
 				bitmap_set(&always, start, nr);
 				bitmap_clear(&inherit, start, nr);
 				bitmap_clear(&madvise, start, nr);
+				bitmap_clear(&defer, start, nr);
 			} else if (!strcmp(policy, "madvise")) {
 				bitmap_set(&madvise, start, nr);
 				bitmap_clear(&inherit, start, nr);
 				bitmap_clear(&always, start, nr);
+				bitmap_clear(&defer, start, nr);
 			} else if (!strcmp(policy, "inherit")) {
 				bitmap_set(&inherit, start, nr);
 				bitmap_clear(&madvise, start, nr);
 				bitmap_clear(&always, start, nr);
+				bitmap_clear(&defer, start, nr);
+			} else if (!strcmp(policy, "defer")) {
+				bitmap_set(&defer, start, nr);
+				bitmap_clear(&madvise, start, nr);
+				bitmap_clear(&always, start, nr);
+				bitmap_clear(&inherit, start, nr);
 			} else if (!strcmp(policy, "never")) {
 				bitmap_clear(&inherit, start, nr);
 				bitmap_clear(&madvise, start, nr);
 				bitmap_clear(&always, start, nr);
+				bitmap_clear(&defer, start, nr);
+
 			} else {
 				pr_err("invalid policy %s in thp_anon boot parameter\n", policy);
 				goto err;
@@ -1064,6 +1090,8 @@ static int __init setup_thp_anon(char *str)
 	huge_anon_orders_always = always;
 	huge_anon_orders_madvise = madvise;
 	huge_anon_orders_inherit = inherit;
+	huge_anon_orders_defer = defer;
+
 	anon_orders_configured = true;
 	return 1;
 
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index fc30698b8e6e..a83bc812ea64 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -488,7 +488,7 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
 {
 	if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
 	    hugepage_pmd_enabled()) {
-		if (thp_vma_allowable_order(vma, vm_flags, TVA_ENFORCE_SYSFS,
+		if (thp_vma_allowable_order(vma, vm_flags, TVA_IN_KHUGEPAGE,
 					    PMD_ORDER))
 			__khugepaged_enter(vma->vm_mm);
 	}
@@ -943,7 +943,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
 				   struct collapse_control *cc, int order)
 {
 	struct vm_area_struct *vma;
-	unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
+	unsigned long tva_flags = cc->is_khugepaged ? TVA_IN_KHUGEPAGE  : 0;
 
 	if (unlikely(khugepaged_test_exit_or_disable(mm)))
 		return SCAN_ANY_PROCESS;
@@ -1393,7 +1393,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 	bool writable = false;
 	int chunk_none_count = 0;
 	int scaled_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - MIN_MTHP_ORDER);
-	unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
+	unsigned long tva_flags = cc->is_khugepaged ? TVA_IN_KHUGEPAGE : 0;
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
 	result = find_pmd_or_thp_or_none(mm, address, &pmd);
@@ -2505,7 +2505,7 @@ static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *
 				   struct collapse_control *cc)
 {
 	int result = SCAN_FAIL;
-	unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
+	unsigned long tva_flags = cc->is_khugepaged ? TVA_IN_KHUGEPAGE : 0;
 
 	if (!*mmap_locked) {
 		mmap_read_lock(mm);
@@ -2595,7 +2595,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
 			break;
 		}
 		if (!thp_vma_allowable_order(vma, vma->vm_flags,
-					TVA_ENFORCE_SYSFS, PMD_ORDER)) {
+					TVA_IN_KHUGEPAGE, PMD_ORDER)) {
 skip:
 			progress++;
 			continue;
-- 
2.48.1