Since we already have list of mm_struct in the system, add a module to
scan each mm that walks VMAs of each mm_struct and scan all the pages
associated with that.
In the scan path: Check for the recently acccessed pages (folios) belonging to
slowtier nodes. Add all those folios to a migration list.
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxx>
---
mm/kmmscand.c | 268 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 264 insertions(+), 4 deletions(-)
diff --git a/mm/kmmscand.c b/mm/kmmscand.c
index 957128d4e425..0496359d07f5 100644
--- a/mm/kmmscand.c
+++ b/mm/kmmscand.c
@@ -4,12 +4,19 @@
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/mmu_notifier.h>
+#include <linux/rmap.h>
+#include <linux/pagewalk.h>
+#include <linux/page_ext.h>
+#include <linux/page_idle.h>
+#include <linux/page_table_check.h>
+#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/mm_inline.h>
#include <linux/kthread.h>
#include <linux/kmmscand.h>
+#include <linux/memory-tiers.h>
+#include <linux/mempolicy.h>
#include <linux/string.h>
-#include <linux/delay.h>
#include <linux/cleanup.h>
#include <asm/pgalloc.h>
@@ -32,6 +39,7 @@ static bool need_wakeup;
static unsigned long kmmscand_sleep_expire;
static DEFINE_SPINLOCK(kmmscand_mm_lock);
+static DEFINE_SPINLOCK(kmmscand_migrate_lock);
static DECLARE_WAIT_QUEUE_HEAD(kmmscand_wait);
#define KMMSCAND_SLOT_HASH_BITS 10
@@ -41,6 +49,7 @@ static struct kmem_cache *kmmscand_slot_cache __read_mostly;
struct kmmscand_mm_slot {
struct mm_slot slot;
+ long address;
};
struct kmmscand_scan {
@@ -52,6 +61,21 @@ struct kmmscand_scan kmmscand_scan = {
.mm_head = LIST_HEAD_INIT(kmmscand_scan.mm_head),
};
+struct kmmscand_migrate_list {
+ struct list_head migrate_head;
+};
+
+struct kmmscand_migrate_list kmmscand_migrate_list = {
+ .migrate_head = LIST_HEAD_INIT(kmmscand_migrate_list.migrate_head),
+};
+
+struct kmmscand_migrate_info {
+ struct list_head migrate_node;
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ struct folio *folio;
+ unsigned long address;
+};
static int kmmscand_has_work(void)
{
return !list_empty(&kmmscand_scan.mm_head);
@@ -84,8 +108,140 @@ static void kmmscand_wait_work(void)
}
}
-static void kmmscand_migrate_folio(void)
+static bool kmmscand_eligible_srcnid(int nid)
{
+ if (!node_is_toptier(nid))
+ return true;
+ return false;
+}
+
+static bool folio_idle_clear_pte_refs_one(struct folio *folio,
+ struct vm_area_struct *vma,
+ unsigned long addr,
+ pte_t *ptep)
+{
+ bool referenced = false;
+ struct mm_struct *mm = vma->vm_mm;
+ pmd_t *pmd = pmd_off(mm, addr);
+
+ if (ptep) {
+ if (ptep_clear_young_notify(vma, addr, ptep))
+ referenced = true;
+ } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+ if (!pmd_present(*pmd))
+ WARN_ON_ONCE(1);
+ if (pmdp_clear_young_notify(vma, addr, pmd))
+ referenced = true;
+ } else {
+ WARN_ON_ONCE(1);
+ }
+
+ if (referenced) {
+ folio_clear_idle(folio);
+ folio_set_young(folio);
+ }
+ return true;
+}
+
+static void page_idle_clear_pte_refs(struct page *page, pte_t *pte, struct mm_walk *walk)
+{
+ bool need_lock;
+ struct folio *folio = page_folio(page);
+ unsigned long address;
+
+ if (!folio_mapped(folio) || !folio_raw_mapping(folio))
+ return;
+
+ need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
+ if (need_lock && !folio_trylock(folio))
+ return;
+ address = vma_address(walk->vma, page_pgoff(folio, page), compound_nr(page));
+ VM_BUG_ON_VMA(address == -EFAULT, vma);
+ folio_idle_clear_pte_refs_one(folio, walk->vma, address, pte);
+
+ if (need_lock)
+ folio_unlock(folio);
+}
+
+static int hot_vma_idle_pte_entry(pte_t *pte,
+ unsigned long addr,
+ unsigned long next,
+ struct mm_walk *walk)
+{
+ struct page *page;
+ struct folio *folio;
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ struct kmmscand_migrate_info *info;
+ struct kmmscand_migrate_list *migrate_list = walk->private;
+ int srcnid;
+
+ pte_t pteval = ptep_get(pte);
+
+ if (pte_none(pteval))
+ return 1;
+ vma = walk->vma;
+ mm = vma->vm_mm;
+ page = pte_page(*pte);
+
+ page_idle_clear_pte_refs(page, pte, walk);
+
+ folio = page_folio(page);
+ folio_get(folio);
+
+ if (!folio || folio_is_zone_device(folio)) {
+ folio_put(folio);
+ return 1;
+ }
+
+ srcnid = folio_nid(folio);
+
+ if (!folio_test_idle(folio) || folio_test_young(folio) ||
+ mmu_notifier_test_young(mm, addr) ||
+ folio_test_referenced(folio) || pte_young(pteval)) {
+
+ /* Do not try to promote pages from regular nodes */
+ if (!kmmscand_eligible_srcnid(srcnid))
+ goto end;
+
+ info = kzalloc(sizeof(struct kmmscand_migrate_info), GFP_KERNEL);
+ if (info && migrate_list) {
+
+ info->mm = mm;
+ info->vma = vma;
+ info->folio = folio;
+
+ spin_lock(&kmmscand_migrate_lock);
+ list_add_tail(&info->migrate_node, &migrate_list->migrate_head);
+ spin_unlock(&kmmscand_migrate_lock);
+ }
+ }
+end:
+ folio_set_idle(folio);
+ folio_put(folio);
+ return 0;
+}
+
+static const struct mm_walk_ops hot_vma_set_idle_ops = {
+ .pte_entry = hot_vma_idle_pte_entry,
+ .walk_lock = PGWALK_RDLOCK,
+};
+
+static void kmmscand_walk_page_vma(struct vm_area_struct *vma)
+{
+ if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
+ is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
+ return;
+ }
+
+ if (!vma->vm_mm ||
+ (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
+ return;
+
+ if (!vma_is_accessible(vma))
+ return;
+
+ walk_page_vma(vma, &hot_vma_set_idle_ops, &kmmscand_migrate_list);
}
static inline int kmmscand_test_exit(struct mm_struct *mm)
@@ -93,10 +249,113 @@ static inline int kmmscand_test_exit(struct mm_struct *mm)
return atomic_read(&mm->mm_users) == 0;
}
+static void kmmscand_collect_mm_slot(struct kmmscand_mm_slot *mm_slot)
+{
+ struct mm_slot *slot = &mm_slot->slot;
+ struct mm_struct *mm = slot->mm;
+
+ lockdep_assert_held(&kmmscand_mm_lock);
+
+ if (kmmscand_test_exit(mm)) {
+ /* free mm_slot */
+ hash_del(&slot->hash);
+ list_del(&slot->mm_node);
+
+ mm_slot_free(kmmscand_slot_cache, mm_slot);
+ mmdrop(mm);
+ }
+}
+
+static void kmmscand_migrate_folio(void)
+{
+}
+
static unsigned long kmmscand_scan_mm_slot(void)
{
- /* placeholder for scanning */
- msleep(100);
+ bool update_mmslot_info = false;
+
+ unsigned long address;
+
+ struct mm_slot *slot;
+ struct mm_struct *mm;
+ struct vma_iterator vmi;
+ struct vm_area_struct *vma = NULL;
+ struct kmmscand_mm_slot *mm_slot;
+
+ /* Retrieve mm */
+ spin_lock(&kmmscand_mm_lock);
+
+ if (kmmscand_scan.mm_slot) {
+ mm_slot = kmmscand_scan.mm_slot;
+ slot = &mm_slot->slot;
+ address = mm_slot->address;
+ } else {
+ slot = list_entry(kmmscand_scan.mm_head.next,
+ struct mm_slot, mm_node);
+ mm_slot = mm_slot_entry(slot, struct kmmscand_mm_slot, slot);
+ address = mm_slot->address;
+ kmmscand_scan.mm_slot = mm_slot;
+ }
+
+ mm = slot->mm;
+
+ spin_unlock(&kmmscand_mm_lock);
+
+ if (unlikely(!mmap_read_trylock(mm)))
+ goto outerloop_mmap_lock;
+
+ if (unlikely(kmmscand_test_exit(mm)))
+ goto outerloop;
+
+
+ vma_iter_init(&vmi, mm, address);
+
+ for_each_vma(vmi, vma) {
+ /* Count the scanned pages here to decide exit */
+ kmmscand_walk_page_vma(vma);
+
+ address = vma->vm_end;
+ }
+
+ if (!vma)
+ address = 0;
+
+ update_mmslot_info = true;
+
+outerloop:
+ /* exit_mmap will destroy ptes after this */
+ mmap_read_unlock(mm);
+
+outerloop_mmap_lock:
+ spin_lock(&kmmscand_mm_lock);
+ VM_BUG_ON(kmmscand_scan.mm_slot != mm_slot);
+
+ if (update_mmslot_info)
+ mm_slot->address = address;
+ /*
+ * Release the current mm_slot if this mm is about to die, or
+ * if we scanned all vmas of this mm.
+ */
+ if (unlikely(kmmscand_test_exit(mm)) || !vma) {
+ /*
+ * Make sure that if mm_users is reaching zero while
+ * kmmscand runs here, kmmscand_exit will find
+ * mm_slot not pointing to the exiting mm.
+ */
+ if (slot->mm_node.next != &kmmscand_scan.mm_head) {
+ slot = list_entry(slot->mm_node.next,
+ struct mm_slot, mm_node);
+ kmmscand_scan.mm_slot =
+ mm_slot_entry(slot, struct kmmscand_mm_slot, slot);
+
+ } else
+ kmmscand_scan.mm_slot = NULL;
+
+ if (kmmscand_test_exit(mm))
+ kmmscand_collect_mm_slot(mm_slot);
+ }
+
+ spin_unlock(&kmmscand_mm_lock);
return 0;
}
@@ -159,6 +418,7 @@ void __kmmscand_enter(struct mm_struct *mm)
if (!kmmscand_slot)
return;
+ kmmscand_slot->address = 0;
slot = &kmmscand_slot->slot;
spin_lock(&kmmscand_mm_lock);
--
2.39.3
