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Also add a config option for the same. High level design: While (1): scan the slowtier pages belonging to VMAs of a task. Add to migation list Separate thread: migrate scanned pages to a toptier node based on heuristics The overall code is heavily influenced by khugepaged design. Signed-off-by: Raghavendra K T --- mm/Kconfig | 8 +++ mm/Makefile | 1 + mm/kmmscand.c | 176 ++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 185 insertions(+) create mode 100644 mm/kmmscand.c diff --git a/mm/Kconfig b/mm/Kconfig index 1b501db06417..5a4931633e15 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -783,6 +783,14 @@ config KSM until a program has madvised that an area is MADV_MERGEABLE, and root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). +config KMMSCAND + bool "Enable PTE A bit scanning and Migration" + depends on NUMA_BALANCING + help + Enable PTE A bit scanning of page. CXL pages accessed are migrated to + a regular NUMA node. The option creates a separate kthread for + scanning and migration. + config DEFAULT_MMAP_MIN_ADDR int "Low address space to protect from user allocation" depends on MMU diff --git a/mm/Makefile b/mm/Makefile index 850386a67b3e..45e2f8cc8fd6 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -94,6 +94,7 @@ obj-$(CONFIG_FAIL_PAGE_ALLOC) += fail_page_alloc.o obj-$(CONFIG_MEMTEST) += memtest.o obj-$(CONFIG_MIGRATION) += migrate.o obj-$(CONFIG_NUMA) += memory-tiers.o +obj-$(CONFIG_KMMSCAND) += kmmscand.o obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o obj-$(CONFIG_PAGE_COUNTER) += page_counter.o diff --git a/mm/kmmscand.c b/mm/kmmscand.c new file mode 100644 index 000000000000..6c55250b5cfb --- /dev/null +++ b/mm/kmmscand.c @@ -0,0 +1,176 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include "internal.h" + + +static struct task_struct *kmmscand_thread __read_mostly; +static DEFINE_MUTEX(kmmscand_mutex); + +/* How long to pause between two scan and migration cycle */ +static unsigned int kmmscand_scan_sleep_ms __read_mostly = 16; + +/* Max number of mms to scan in one scan and migration cycle */ +#define KMMSCAND_MMS_TO_SCAN (4 * 1024UL) +static unsigned long kmmscand_mms_to_scan __read_mostly = KMMSCAND_MMS_TO_SCAN; + +bool kmmscand_scan_enabled = true; +static bool need_wakeup; + +static unsigned long kmmscand_sleep_expire; + +static DECLARE_WAIT_QUEUE_HEAD(kmmscand_wait); + +struct kmmscand_scan { + struct list_head mm_head; +}; + +struct kmmscand_scan kmmscand_scan = { + .mm_head = LIST_HEAD_INIT(kmmscand_scan.mm_head), +}; + +static int kmmscand_has_work(void) +{ + return !list_empty(&kmmscand_scan.mm_head); +} + +static bool kmmscand_should_wakeup(void) +{ + bool wakeup = kthread_should_stop() || need_wakeup || + time_after_eq(jiffies, kmmscand_sleep_expire); + if (need_wakeup) + need_wakeup = false; + + return wakeup; +} + +static void kmmscand_wait_work(void) +{ + const unsigned long scan_sleep_jiffies = + msecs_to_jiffies(kmmscand_scan_sleep_ms); + + if (!scan_sleep_jiffies) + return; + + kmmscand_sleep_expire = jiffies + scan_sleep_jiffies; + wait_event_timeout(kmmscand_wait, + kmmscand_should_wakeup(), + scan_sleep_jiffies); + return; +} + +static unsigned long kmmscand_scan_mm_slot(void) +{ + /* placeholder for scanning */ + msleep(100); + return 0; +} + +static void kmmscand_do_scan(void) +{ + unsigned long iter = 0, mms_to_scan; + + mms_to_scan = READ_ONCE(kmmscand_mms_to_scan); + + while (true) { + cond_resched(); + + if (unlikely(kthread_should_stop()) || + !READ_ONCE(kmmscand_scan_enabled)) + break; + + if (kmmscand_has_work()) + kmmscand_scan_mm_slot(); + + iter++; + if (iter >= mms_to_scan) + break; + } +} + +static int kmmscand(void *none) +{ + for (;;) { + if (unlikely(kthread_should_stop())) + break; + + kmmscand_do_scan(); + + while (!READ_ONCE(kmmscand_scan_enabled)) { + cpu_relax(); + kmmscand_wait_work(); + } + + kmmscand_wait_work(); + } + return 0; +} + +static int start_kmmscand(void) +{ + int err = 0; + + guard(mutex)(&kmmscand_mutex); + + /* Some one already succeeded in starting daemon */ + if (kmmscand_thread) + goto end; + + kmmscand_thread = kthread_run(kmmscand, NULL, "kmmscand"); + if (IS_ERR(kmmscand_thread)) { + pr_err("kmmscand: kthread_run(kmmscand) failed\n"); + err = PTR_ERR(kmmscand_thread); + kmmscand_thread = NULL; + goto end; + } else { + pr_info("kmmscand: Successfully started kmmscand"); + } + + if (!list_empty(&kmmscand_scan.mm_head)) + wake_up_interruptible(&kmmscand_wait); + +end: + return err; +} + +static int stop_kmmscand(void) +{ + int err = 0; + + guard(mutex)(&kmmscand_mutex); + + if (kmmscand_thread) { + kthread_stop(kmmscand_thread); + kmmscand_thread = NULL; + } + + return err; +} + +static int __init kmmscand_init(void) +{ + int err; + + err = start_kmmscand(); + if (err) + goto err_kmmscand; + + return 0; + +err_kmmscand: + stop_kmmscand(); + + return err; +} +subsys_initcall(kmmscand_init);