Re: [PATCH 6/6] mm/gup: migrate pinned pages out of movable zone

From: John Hubbard
Date: Thu Dec 03 2020 - 03:23:23 EST


On 12/1/20 9:23 PM, Pavel Tatashin wrote:
We do not allocate pin pages in ZONE_MOVABLE, but if pages were already
allocated before pinning they need to migrated to a different zone.
Currently, we migrate movable CMA pages only. Generalize the function
that migrates CMA pages to migrate all movable pages.

Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
---
include/linux/migrate.h | 1 +
include/trace/events/migrate.h | 3 +-
mm/gup.c | 56 +++++++++++++---------------------
3 files changed, 24 insertions(+), 36 deletions(-)


I like the cleanup so far, even at this point it's a relief to finally
see the nested ifdefs get removed.

One naming nit/idea below, but this looks fine as is, so:

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 0f8d1583fa8e..00bab23d1ee5 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -27,6 +27,7 @@ enum migrate_reason {
MR_MEMPOLICY_MBIND,
MR_NUMA_MISPLACED,
MR_CONTIG_RANGE,
+ MR_LONGTERM_PIN,
MR_TYPES
};
diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
index 4d434398d64d..363b54ce104c 100644
--- a/include/trace/events/migrate.h
+++ b/include/trace/events/migrate.h
@@ -20,7 +20,8 @@
EM( MR_SYSCALL, "syscall_or_cpuset") \
EM( MR_MEMPOLICY_MBIND, "mempolicy_mbind") \
EM( MR_NUMA_MISPLACED, "numa_misplaced") \
- EMe(MR_CONTIG_RANGE, "contig_range")
+ EM( MR_CONTIG_RANGE, "contig_range") \
+ EMe(MR_LONGTERM_PIN, "longterm_pin")
/*
* First define the enums in the above macros to be exported to userspace
diff --git a/mm/gup.c b/mm/gup.c
index 724d8a65e1df..1d511f65f8a7 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1593,19 +1593,18 @@ static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
}
#endif
-#ifdef CONFIG_CMA
-static long check_and_migrate_cma_pages(struct mm_struct *mm,
- unsigned long start,
- unsigned long nr_pages,
- struct page **pages,
- struct vm_area_struct **vmas,
- unsigned int gup_flags)
+static long check_and_migrate_movable_pages(struct mm_struct *mm,
+ unsigned long start,
+ unsigned long nr_pages,
+ struct page **pages,
+ struct vm_area_struct **vmas,
+ unsigned int gup_flags)
{
unsigned long i;
unsigned long step;
bool drain_allow = true;
bool migrate_allow = true;
- LIST_HEAD(cma_page_list);
+ LIST_HEAD(page_list);


Maybe naming it "movable_page_list", would be a nice touch.


thanks,
--
John Hubbard
NVIDIA

long ret = nr_pages;
struct migration_target_control mtc = {
.nid = NUMA_NO_NODE,
@@ -1623,13 +1622,12 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
*/
step = compound_nr(head) - (pages[i] - head);
/*
- * If we get a page from the CMA zone, since we are going to
- * be pinning these entries, we might as well move them out
- * of the CMA zone if possible.
+ * If we get a movable page, since we are going to be pinning
+ * these entries, try to move them out if possible.
*/
- if (is_migrate_cma_page(head)) {
+ if (is_migrate_movable(get_pageblock_migratetype(head))) {
if (PageHuge(head))
- isolate_huge_page(head, &cma_page_list);
+ isolate_huge_page(head, &page_list);
else {
if (!PageLRU(head) && drain_allow) {
lru_add_drain_all();
@@ -1637,7 +1635,7 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
}
if (!isolate_lru_page(head)) {
- list_add_tail(&head->lru, &cma_page_list);
+ list_add_tail(&head->lru, &page_list);
mod_node_page_state(page_pgdat(head),
NR_ISOLATED_ANON +
page_is_file_lru(head),
@@ -1649,7 +1647,7 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
i += step;
}
- if (!list_empty(&cma_page_list)) {
+ if (!list_empty(&page_list)) {
/*
* drop the above get_user_pages reference.
*/
@@ -1659,7 +1657,7 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
for (i = 0; i < nr_pages; i++)
put_page(pages[i]);
- if (migrate_pages(&cma_page_list, alloc_migration_target, NULL,
+ if (migrate_pages(&page_list, alloc_migration_target, NULL,
(unsigned long)&mtc, MIGRATE_SYNC, MR_CONTIG_RANGE)) {
/*
* some of the pages failed migration. Do get_user_pages
@@ -1667,17 +1665,16 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
*/
migrate_allow = false;
- if (!list_empty(&cma_page_list))
- putback_movable_pages(&cma_page_list);
+ if (!list_empty(&page_list))
+ putback_movable_pages(&page_list);
}
/*
* We did migrate all the pages, Try to get the page references
- * again migrating any new CMA pages which we failed to isolate
- * earlier.
+ * again migrating any pages which we failed to isolate earlier.
*/
ret = __get_user_pages_locked(mm, start, nr_pages,
- pages, vmas, NULL,
- gup_flags);
+ pages, vmas, NULL,
+ gup_flags);
if ((ret > 0) && migrate_allow) {
nr_pages = ret;
@@ -1688,17 +1685,6 @@ static long check_and_migrate_cma_pages(struct mm_struct *mm,
return ret;
}
-#else
-static long check_and_migrate_cma_pages(struct mm_struct *mm,
- unsigned long start,
- unsigned long nr_pages,
- struct page **pages,
- struct vm_area_struct **vmas,
- unsigned int gup_flags)
-{
- return nr_pages;
-}
-#endif /* CONFIG_CMA */
/*
* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
@@ -1746,8 +1732,8 @@ static long __gup_longterm_locked(struct mm_struct *mm,
goto out;
}
- rc = check_and_migrate_cma_pages(mm, start, rc, pages,
- vmas_tmp, gup_flags);
+ rc = check_and_migrate_movable_pages(mm, start, rc, pages,
+ vmas_tmp, gup_flags);
out:
memalloc_nomovable_restore(flags);
}