Now page copies are batched, multi-threaded page copy can be used to
increase page copy throughput. Add copy_page_lists_mt() to copy pages in
multi-threaded manners. Empirical data show more than 32 base pages are
needed to show the benefit of using multi-threaded page copy, so use 32 as
the threshold.
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
include/linux/migrate.h | 3 +
mm/Makefile | 2 +-
mm/copy_pages.c | 186 ++++++++++++++++++++++++++++++++++++++++
mm/migrate.c | 19 ++--
4 files changed, 199 insertions(+), 11 deletions(-)
create mode 100644 mm/copy_pages.c
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 29919faea2f1..a0124f4893b0 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -80,6 +80,9 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio);
int folio_migrate_mapping(struct address_space *mapping,
struct folio *newfolio, struct folio *folio, int extra_count);
+int copy_page_lists_mt(struct list_head *dst_folios,
+ struct list_head *src_folios, int nr_items);
+
#else
static inline void putback_movable_pages(struct list_head *l) {}
diff --git a/mm/Makefile b/mm/Makefile
index 850386a67b3e..f8c7f6b4cebb 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -92,7 +92,7 @@ obj-$(CONFIG_KMSAN) += kmsan/
obj-$(CONFIG_FAILSLAB) += failslab.o
obj-$(CONFIG_FAIL_PAGE_ALLOC) += fail_page_alloc.o
obj-$(CONFIG_MEMTEST) += memtest.o
-obj-$(CONFIG_MIGRATION) += migrate.o
+obj-$(CONFIG_MIGRATION) += migrate.o copy_pages.o
obj-$(CONFIG_NUMA) += memory-tiers.o
obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
diff --git a/mm/copy_pages.c b/mm/copy_pages.c
new file mode 100644
index 000000000000..0e2231199f66
--- /dev/null
+++ b/mm/copy_pages.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Parallel page copy routine.
+ */
+
+#include <linux/sysctl.h>
+#include <linux/highmem.h>
+#include <linux/workqueue.h>
+#include <linux/slab.h>
+#include <linux/migrate.h>
+
+
+unsigned int limit_mt_num = 4;
+
+struct copy_item {
+ char *to;
+ char *from;
+ unsigned long chunk_size;
+};
+
+struct copy_page_info {
+ struct work_struct copy_page_work;
+ unsigned long num_items;
+ struct copy_item item_list[];
+};
+
+static void copy_page_routine(char *vto, char *vfrom,
+ unsigned long chunk_size)
+{
+ memcpy(vto, vfrom, chunk_size);
+}
+
+static void copy_page_work_queue_thread(struct work_struct *work)
+{
+ struct copy_page_info *my_work = (struct copy_page_info *)work;
+ int i;
+
+ for (i = 0; i < my_work->num_items; ++i)
+ copy_page_routine(my_work->item_list[i].to,
+ my_work->item_list[i].from,
+ my_work->item_list[i].chunk_size);
+}
+
+int copy_page_lists_mt(struct list_head *dst_folios,
+ struct list_head *src_folios, int nr_items)
+{
+ int err = 0;
+ unsigned int total_mt_num = limit_mt_num;
+ int to_node = folio_nid(list_first_entry(dst_folios, struct folio, lru));
+ int i;
+ struct copy_page_info *work_items[32] = {0};
+ const struct cpumask *per_node_cpumask = cpumask_of_node(to_node);
+ int cpu_id_list[32] = {0};
+ int cpu;
+ int max_items_per_thread;
+ int item_idx;
+ struct folio *src, *src2, *dst, *dst2;
+
+ total_mt_num = min_t(unsigned int, total_mt_num,
+ cpumask_weight(per_node_cpumask));
+
+ if (total_mt_num > 32)
+ total_mt_num = 32;
+
+ /* Each threads get part of each page, if nr_items < totla_mt_num */
+ if (nr_items < total_mt_num)
+ max_items_per_thread = nr_items;
+ else
+ max_items_per_thread = (nr_items / total_mt_num) +
+ ((nr_items % total_mt_num) ? 1 : 0);
+
+
+ for (cpu = 0; cpu < total_mt_num; ++cpu) {
+ work_items[cpu] = kzalloc(sizeof(struct copy_page_info) +
+ sizeof(struct copy_item) * max_items_per_thread,
+ GFP_NOWAIT);
+ if (!work_items[cpu]) {
+ err = -ENOMEM;
+ goto free_work_items;
+ }
+ }
+
+ i = 0;
+ /* TODO: need a better cpu selection method */
+ for_each_cpu(cpu, per_node_cpumask) {
+ if (i >= total_mt_num)
+ break;
+ cpu_id_list[i] = cpu;
+ ++i;
+ }
+
+ if (nr_items < total_mt_num) {
+ for (cpu = 0; cpu < total_mt_num; ++cpu) {
+ INIT_WORK((struct work_struct *)work_items[cpu],
+ copy_page_work_queue_thread);
+ work_items[cpu]->num_items = max_items_per_thread;
+ }
+
+ item_idx = 0;
+ dst = list_first_entry(dst_folios, struct folio, lru);
+ dst2 = list_next_entry(dst, lru);
+ list_for_each_entry_safe(src, src2, src_folios, lru) {
+ unsigned long chunk_size = PAGE_SIZE * folio_nr_pages(src) / total_mt_num;
+ /* XXX: not working in HIGHMEM */
+ char *vfrom = page_address(&src->page);
+ char *vto = page_address(&dst->page);
+
+ VM_WARN_ON(PAGE_SIZE * folio_nr_pages(src) % total_mt_num);
+ VM_WARN_ON(folio_nr_pages(dst) != folio_nr_pages(src));
+
+ for (cpu = 0; cpu < total_mt_num; ++cpu) {
+ work_items[cpu]->item_list[item_idx].to =
+ vto + chunk_size * cpu;
+ work_items[cpu]->item_list[item_idx].from =
+ vfrom + chunk_size * cpu;
+ work_items[cpu]->item_list[item_idx].chunk_size =
+ chunk_size;
+ }
+
+ item_idx++;
+ dst = dst2;
+ dst2 = list_next_entry(dst, lru);
+ }
+
+ for (cpu = 0; cpu < total_mt_num; ++cpu)
+ queue_work_on(cpu_id_list[cpu],
+ system_unbound_wq,
+ (struct work_struct *)work_items[cpu]);
+ } else {
+ int num_xfer_per_thread = nr_items / total_mt_num;
+ int per_cpu_item_idx;
+
+
+ for (cpu = 0; cpu < total_mt_num; ++cpu) {
+ INIT_WORK((struct work_struct *)work_items[cpu],
+ copy_page_work_queue_thread);
+
+ work_items[cpu]->num_items = num_xfer_per_thread +
+ (cpu < (nr_items % total_mt_num));
+ }
+
+ cpu = 0;
+ per_cpu_item_idx = 0;
+ item_idx = 0;
+ dst = list_first_entry(dst_folios, struct folio, lru);
+ dst2 = list_next_entry(dst, lru);
+ list_for_each_entry_safe(src, src2, src_folios, lru) {
+ /* XXX: not working in HIGHMEM */
+ work_items[cpu]->item_list[per_cpu_item_idx].to =
+ page_address(&dst->page);
+ work_items[cpu]->item_list[per_cpu_item_idx].from =
+ page_address(&src->page);
+ work_items[cpu]->item_list[per_cpu_item_idx].chunk_size =
+ PAGE_SIZE * folio_nr_pages(src);
+
+ VM_WARN_ON(folio_nr_pages(dst) !=
+ folio_nr_pages(src));
+
+ per_cpu_item_idx++;
+ item_idx++;
+ dst = dst2;
+ dst2 = list_next_entry(dst, lru);
+
+ if (per_cpu_item_idx == work_items[cpu]->num_items) {
+ queue_work_on(cpu_id_list[cpu],
+ system_unbound_wq,
+ (struct work_struct *)work_items[cpu]);
+ per_cpu_item_idx = 0;
+ cpu++;
+ }
+ }
+ if (item_idx != nr_items)
+ pr_warn("%s: only %d out of %d pages are transferred\n",
+ __func__, item_idx - 1, nr_items);
+ }
+
+ /* Wait until it finishes */
+ for (i = 0; i < total_mt_num; ++i)
+ flush_work((struct work_struct *)work_items[i]);
+
+free_work_items:
+ for (cpu = 0; cpu < total_mt_num; ++cpu)
+ kfree(work_items[cpu]);
+
+ return err;
+}
diff --git a/mm/migrate.c b/mm/migrate.c
index 95c4cc4a7823..18440180d747 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1799,7 +1799,7 @@ static void migrate_folios_batch_move(struct list_head *src_folios,
int *nr_retry_pages)
{
struct folio *folio, *folio2, *dst, *dst2;
- int rc, nr_pages = 0, nr_mig_folios = 0;
+ int rc, nr_pages = 0, total_nr_pages = 0, total_nr_folios = 0;
int old_page_state = 0;
struct anon_vma *anon_vma = NULL;
bool is_lru;
@@ -1807,11 +1807,6 @@ static void migrate_folios_batch_move(struct list_head *src_folios,
LIST_HEAD(err_src);
LIST_HEAD(err_dst);
- if (mode != MIGRATE_ASYNC) {
- *retry += 1;
- return;
- }
-
/*
* Iterate over the list of locked src/dst folios to copy the metadata
*/
@@ -1859,19 +1854,23 @@ static void migrate_folios_batch_move(struct list_head *src_folios,
migrate_folio_undo_src(folio, old_page_state & PAGE_WAS_MAPPED,
anon_vma, true, ret_folios);
migrate_folio_undo_dst(dst, true, put_new_folio, private);
- } else /* MIGRATEPAGE_SUCCESS */
- nr_mig_folios++;
+ } else { /* MIGRATEPAGE_SUCCESS */
+ total_nr_pages += nr_pages;
+ total_nr_folios++;
+ }
dst = dst2;
dst2 = list_next_entry(dst, lru);
}
/* Exit if folio list for batch migration is empty */
- if (!nr_mig_folios)
+ if (!total_nr_pages)
goto out;
/* Batch copy the folios */
- {
+ if (total_nr_pages > 32) {
+ copy_page_lists_mt(dst_folios, src_folios, total_nr_folios);
+ } else {
dst = list_first_entry(dst_folios, struct folio, lru);
dst2 = list_next_entry(dst, lru);
list_for_each_entry_safe(folio, folio2, src_folios, lru) {
--
2.45.2
