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bool kmmscand_scan_enabled = true; static bool need_wakeup; +static bool migrated_need_wakeup; + +/* How long to pause between two migration cycles */ +static unsigned int kmmmigrate_sleep_ms __read_mostly = 20; + +static struct task_struct *kmmmigrated_thread __read_mostly; +static DEFINE_MUTEX(kmmmigrated_mutex); +static DECLARE_WAIT_QUEUE_HEAD(kmmmigrated_wait); +static unsigned long kmmmigrated_sleep_expire; + +/* mm of the migrating folio entry */ +static struct mm_struct *kmmscand_cur_migrate_mm; + +/* Migration list is manipulated underneath because of mm_exit */ +static bool kmmscand_migration_list_dirty; 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 @@ -80,6 +97,14 @@ struct kmmscand_scanctrl { struct kmmscand_scanctrl kmmscand_scanctrl; +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), +}; + /* Per folio information used for migration */ struct kmmscand_migrate_info { struct list_head migrate_node; @@ -101,6 +126,13 @@ static int kmmscand_has_work(void) return !list_empty(&kmmscand_scan.mm_head); } +static int kmmmigrated_has_work(void) +{ + if (!list_empty(&kmmscand_migrate_list.migrate_head)) + return true; + return false; +} + static bool kmmscand_should_wakeup(void) { bool wakeup = kthread_should_stop() || need_wakeup || @@ -111,6 +143,16 @@ static bool kmmscand_should_wakeup(void) return wakeup; } +static bool kmmmigrated_should_wakeup(void) +{ + bool wakeup = kthread_should_stop() || migrated_need_wakeup || + time_after_eq(jiffies, kmmmigrated_sleep_expire); + if (migrated_need_wakeup) + migrated_need_wakeup = false; + + return wakeup; +} + static void kmmscand_wait_work(void) { const unsigned long scan_sleep_jiffies = @@ -126,6 +168,19 @@ static void kmmscand_wait_work(void) return; } +static void kmmmigrated_wait_work(void) +{ + const unsigned long migrate_sleep_jiffies = + msecs_to_jiffies(kmmmigrate_sleep_ms); + + if (!migrate_sleep_jiffies) + return; + + kmmmigrated_sleep_expire = jiffies + migrate_sleep_jiffies; + wait_event_timeout(kmmmigrated_wait, + kmmmigrated_should_wakeup(), + migrate_sleep_jiffies); +} static inline bool is_valid_folio(struct folio *folio) { @@ -238,7 +293,6 @@ static int hot_vma_idle_pte_entry(pte_t *pte, folio_put(folio); return 0; } - /* XXX: Leaking memory. TBD: consume info */ info = kzalloc(sizeof(struct kmmscand_migrate_info), GFP_NOWAIT); if (info && scanctrl) { @@ -282,6 +336,28 @@ static inline int kmmscand_test_exit(struct mm_struct *mm) return atomic_read(&mm->mm_users) == 0; } +static void kmmscand_cleanup_migration_list(struct mm_struct *mm) +{ + struct kmmscand_migrate_info *info, *tmp; + + spin_lock(&kmmscand_migrate_lock); + if (!list_empty(&kmmscand_migrate_list.migrate_head)) { + if (mm == READ_ONCE(kmmscand_cur_migrate_mm)) { + /* A folio in this mm is being migrated. wait */ + WRITE_ONCE(kmmscand_migration_list_dirty, true); + } + + list_for_each_entry_safe(info, tmp, &kmmscand_migrate_list.migrate_head, + migrate_node) { + if (info && (info->mm == mm)) { + info->mm = NULL; + WRITE_ONCE(kmmscand_migration_list_dirty, true); + } + } + } + spin_unlock(&kmmscand_migrate_lock); +} + static void kmmscand_collect_mm_slot(struct kmmscand_mm_slot *mm_slot) { struct mm_slot *slot = &mm_slot->slot; @@ -294,11 +370,17 @@ static void kmmscand_collect_mm_slot(struct kmmscand_mm_slot *mm_slot) hash_del(&slot->hash); list_del(&slot->mm_node); + kmmscand_cleanup_migration_list(mm); + mm_slot_free(kmmscand_slot_cache, mm_slot); mmdrop(mm); } } +static void kmmscand_migrate_folio(void) +{ +} + static unsigned long kmmscand_scan_mm_slot(void) { bool next_mm = false; @@ -347,9 +429,17 @@ static unsigned long kmmscand_scan_mm_slot(void) if (vma_scanned_size >= kmmscand_scan_size) { next_mm = true; - /* TBD: Add scanned folios to migration list */ + /* Add scanned folios to migration list */ + spin_lock(&kmmscand_migrate_lock); + list_splice_tail_init(&kmmscand_scanctrl.scan_list, + &kmmscand_migrate_list.migrate_head); + spin_unlock(&kmmscand_migrate_lock); break; } + spin_lock(&kmmscand_migrate_lock); + list_splice_tail_init(&kmmscand_scanctrl.scan_list, + &kmmscand_migrate_list.migrate_head); + spin_unlock(&kmmscand_migrate_lock); } if (!vma) @@ -478,7 +568,7 @@ void __kmmscand_exit(struct mm_struct *mm) { struct kmmscand_mm_slot *mm_slot; struct mm_slot *slot; - int free = 0; + int free = 0, serialize = 1; spin_lock(&kmmscand_mm_lock); slot = mm_slot_lookup(kmmscand_slots_hash, mm); @@ -493,10 +583,15 @@ void __kmmscand_exit(struct mm_struct *mm) free = 1; /* TBD: Set the actual next slot */ kmmscand_scan.mm_slot = NULL; + } else if (mm_slot && kmmscand_scan.mm_slot == mm_slot && mm_slot->is_scanned) { + serialize = 0; } spin_unlock(&kmmscand_mm_lock); + if (serialize) + kmmscand_cleanup_migration_list(mm); + if (free) { mm_slot_free(kmmscand_slot_cache, mm_slot); mmdrop(mm); @@ -546,10 +641,59 @@ static int stop_kmmscand(void) return err; } +static int kmmmigrated(void *arg) +{ + for (;;) { + WRITE_ONCE(migrated_need_wakeup, false); + if (unlikely(kthread_should_stop())) + break; + if (kmmmigrated_has_work()) + kmmscand_migrate_folio(); + msleep(20); + kmmmigrated_wait_work(); + } + return 0; +} + +static int start_kmmmigrated(void) +{ + int err = 0; + + guard(mutex)(&kmmmigrated_mutex); + + /* Someone already succeeded in starting daemon */ + if (kmmmigrated_thread) + goto end; + + kmmmigrated_thread = kthread_run(kmmmigrated, NULL, "kmmmigrated"); + if (IS_ERR(kmmmigrated_thread)) { + pr_err("kmmmigrated: kthread_run(kmmmigrated) failed\n"); + err = PTR_ERR(kmmmigrated_thread); + kmmmigrated_thread = NULL; + goto end; + } else { + pr_info("kmmmigrated: Successfully started kmmmigrated"); + } + + wake_up_interruptible(&kmmmigrated_wait); +end: + return err; +} + +static int stop_kmmmigrated(void) +{ + guard(mutex)(&kmmmigrated_mutex); + kthread_stop(kmmmigrated_thread); + return 0; +} + static void init_list(void) { + INIT_LIST_HEAD(&kmmscand_migrate_list.migrate_head); INIT_LIST_HEAD(&kmmscand_scanctrl.scan_list); + spin_lock_init(&kmmscand_migrate_lock); init_waitqueue_head(&kmmscand_wait); + init_waitqueue_head(&kmmmigrated_wait); } static int __init kmmscand_init(void) @@ -568,8 +712,15 @@ static int __init kmmscand_init(void) if (err) goto err_kmmscand; + err = start_kmmmigrated(); + if (err) + goto err_kmmmigrated; + return 0; +err_kmmmigrated: + stop_kmmmigrated(); + err_kmmscand: stop_kmmscand(); kmmscand_destroy();