The patch titled
Subject: mm: make alloc_contig_range work at pageblock granularity
has been added to the -mm tree. Its filename is
mm-make-alloc_contig_range-work-at-pageblock-granularity.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-make-alloc_contig_range-work-at-pageblock-granularity.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-make-alloc_contig_range-work-at-pageblock-granularity.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm: make alloc_contig_range work at pageblock granularity
alloc_contig_range() worked at MAX_ORDER_NR_PAGES granularity to avoid
merging pageblocks with different migratetypes. It might unnecessarily
convert extra pageblocks at the beginning and at the end of the range.
Change alloc_contig_range() to work at pageblock granularity.
Special handling is needed for free pages and in-use pages across the
boundaries of the range specified by alloc_contig_range(). Because these
partially isolated pages causes free page accounting issues. The free
pages will be split and freed into separate migratetype lists; the in-use
pages will be migrated then the freed pages will be handled in the
aforementioned way.
Link: https://lkml.kernel.org/r/20220425143118.2850746-4-zi.yan@xxxxxxxx
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Eric Ren <renzhengeek@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/page-isolation.h | 4
mm/internal.h | 6 +
mm/memory_hotplug.c | 3
mm/page_alloc.c | 54 +++++++--
mm/page_isolation.c | 184 ++++++++++++++++++++++++++++++-
5 files changed, 233 insertions(+), 18 deletions(-)
--- a/include/linux/page-isolation.h~mm-make-alloc_contig_range-work-at-pageblock-granularity
+++ a/include/linux/page-isolation.h
@@ -42,7 +42,7 @@ int move_freepages_block(struct zone *zo
*/
int
start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
- unsigned migratetype, int flags);
+ int migratetype, int flags, gfp_t gfp_flags);
/*
* Changes MIGRATE_ISOLATE to MIGRATE_MOVABLE.
@@ -50,7 +50,7 @@ start_isolate_page_range(unsigned long s
*/
void
undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
- unsigned migratetype);
+ int migratetype);
/*
* Test all pages in [start_pfn, end_pfn) are isolated or not.
--- a/mm/internal.h~mm-make-alloc_contig_range-work-at-pageblock-granularity
+++ a/mm/internal.h
@@ -359,6 +359,9 @@ extern void *memmap_alloc(phys_addr_t si
phys_addr_t min_addr,
int nid, bool exact_nid);
+void split_free_page(struct page *free_page,
+ int order, unsigned long split_pfn_offset);
+
#if defined CONFIG_COMPACTION || defined CONFIG_CMA
/*
@@ -422,6 +425,9 @@ isolate_freepages_range(struct compact_c
int
isolate_migratepages_range(struct compact_control *cc,
unsigned long low_pfn, unsigned long end_pfn);
+
+int __alloc_contig_migrate_range(struct compact_control *cc,
+ unsigned long start, unsigned long end);
#endif
int find_suitable_fallback(struct free_area *area, unsigned int order,
int migratetype, bool only_stealable, bool *can_steal);
--- a/mm/memory_hotplug.c~mm-make-alloc_contig_range-work-at-pageblock-granularity
+++ a/mm/memory_hotplug.c
@@ -1845,7 +1845,8 @@ int __ref offline_pages(unsigned long st
/* set above range as isolated */
ret = start_isolate_page_range(start_pfn, end_pfn,
MIGRATE_MOVABLE,
- MEMORY_OFFLINE | REPORT_FAILURE);
+ MEMORY_OFFLINE | REPORT_FAILURE,
+ GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL);
if (ret) {
reason = "failure to isolate range";
goto failed_removal_pcplists_disabled;
--- a/mm/page_alloc.c~mm-make-alloc_contig_range-work-at-pageblock-granularity
+++ a/mm/page_alloc.c
@@ -1094,6 +1094,43 @@ done_merging:
page_reporting_notify_free(order);
}
+/**
+ * split_free_page() -- split a free page at split_pfn_offset
+ * @free_page: the original free page
+ * @order: the order of the page
+ * @split_pfn_offset: split offset within the page
+ *
+ * It is used when the free page crosses two pageblocks with different migratetypes
+ * at split_pfn_offset within the page. The split free page will be put into
+ * separate migratetype lists afterwards. Otherwise, the function achieves
+ * nothing.
+ */
+void split_free_page(struct page *free_page,
+ int order, unsigned long split_pfn_offset)
+{
+ struct zone *zone = page_zone(free_page);
+ unsigned long free_page_pfn = page_to_pfn(free_page);
+ unsigned long pfn;
+ unsigned long flags;
+ int free_page_order;
+
+ spin_lock_irqsave(&zone->lock, flags);
+ del_page_from_free_list(free_page, zone, order);
+ for (pfn = free_page_pfn;
+ pfn < free_page_pfn + (1UL << order);) {
+ int mt = get_pfnblock_migratetype(pfn_to_page(pfn), pfn);
+
+ free_page_order = ffs(split_pfn_offset) - 1;
+ __free_one_page(pfn_to_page(pfn), pfn, zone, free_page_order,
+ mt, FPI_NONE);
+ pfn += 1UL << free_page_order;
+ split_pfn_offset -= (1UL << free_page_order);
+ /* we have done the first part, now switch to second part */
+ if (split_pfn_offset == 0)
+ split_pfn_offset = (1UL << order) - (pfn - free_page_pfn);
+ }
+ spin_unlock_irqrestore(&zone->lock, flags);
+}
/*
* A bad page could be due to a number of fields. Instead of multiple branches,
* try and check multiple fields with one check. The caller must do a detailed
@@ -8919,7 +8956,7 @@ static inline void alloc_contig_dump_pag
#endif
/* [start, end) must belong to a single zone. */
-static int __alloc_contig_migrate_range(struct compact_control *cc,
+int __alloc_contig_migrate_range(struct compact_control *cc,
unsigned long start, unsigned long end)
{
/* This function is based on compact_zone() from compaction.c. */
@@ -9002,7 +9039,7 @@ int alloc_contig_range(unsigned long sta
unsigned migratetype, gfp_t gfp_mask)
{
unsigned long outer_start, outer_end;
- unsigned int order;
+ int order;
int ret = 0;
struct compact_control cc = {
@@ -9021,14 +9058,11 @@ int alloc_contig_range(unsigned long sta
* What we do here is we mark all pageblocks in range as
* MIGRATE_ISOLATE. Because pageblock and max order pages may
* have different sizes, and due to the way page allocator
- * work, we align the range to biggest of the two pages so
- * that page allocator won't try to merge buddies from
- * different pageblocks and change MIGRATE_ISOLATE to some
- * other migration type.
+ * work, start_isolate_page_range() has special handlings for this.
*
* Once the pageblocks are marked as MIGRATE_ISOLATE, we
* migrate the pages from an unaligned range (ie. pages that
- * we are interested in). This will put all the pages in
+ * we are interested in). This will put all the pages in
* range back to page allocator as MIGRATE_ISOLATE.
*
* When this is done, we take the pages in range from page
@@ -9042,9 +9076,9 @@ int alloc_contig_range(unsigned long sta
*/
ret = start_isolate_page_range(pfn_max_align_down(start),
- pfn_max_align_up(end), migratetype, 0);
+ pfn_max_align_up(end), migratetype, 0, gfp_mask);
if (ret)
- return ret;
+ goto done;
drain_all_pages(cc.zone);
@@ -9064,7 +9098,7 @@ int alloc_contig_range(unsigned long sta
ret = 0;
/*
- * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
+ * Pages from [start, end) are within a pageblock_nr_pages
* aligned blocks that are marked as MIGRATE_ISOLATE. What's
* more, all pages in [start, end) are free in page allocator.
* What we are going to do is to allocate all pages from
--- a/mm/page_isolation.c~mm-make-alloc_contig_range-work-at-pageblock-granularity
+++ a/mm/page_isolation.c
@@ -203,7 +203,7 @@ static int set_migratetype_isolate(struc
return -EBUSY;
}
-static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
+static void unset_migratetype_isolate(struct page *page, int migratetype)
{
struct zone *zone;
unsigned long flags, nr_pages;
@@ -280,6 +280,157 @@ __first_valid_page(unsigned long pfn, un
}
/**
+ * isolate_single_pageblock() -- tries to isolate a pageblock that might be
+ * within a free or in-use page.
+ * @boundary_pfn: pageblock-aligned pfn that a page might cross
+ * @gfp_flags: GFP flags used for migrating pages
+ * @isolate_before: isolate the pageblock before the boundary_pfn
+ *
+ * Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one
+ * pageblock. When not all pageblocks within a page are isolated at the same
+ * time, free page accounting can go wrong. For example, in the case of
+ * MAX_ORDER-1 = pageblock_order + 1, a MAX_ORDER-1 page has two pagelbocks.
+ * [ MAX_ORDER-1 ]
+ * [ pageblock0 | pageblock1 ]
+ * When either pageblock is isolated, if it is a free page, the page is not
+ * split into separate migratetype lists, which is supposed to; if it is an
+ * in-use page and freed later, __free_one_page() does not split the free page
+ * either. The function handles this by splitting the free page or migrating
+ * the in-use page then splitting the free page.
+ */
+static int isolate_single_pageblock(unsigned long boundary_pfn, gfp_t gfp_flags,
+ bool isolate_before)
+{
+ unsigned char saved_mt;
+ unsigned long start_pfn;
+ unsigned long isolate_pageblock;
+ unsigned long pfn;
+ struct zone *zone;
+
+ VM_BUG_ON(!IS_ALIGNED(boundary_pfn, pageblock_nr_pages));
+
+ if (isolate_before)
+ isolate_pageblock = boundary_pfn - pageblock_nr_pages;
+ else
+ isolate_pageblock = boundary_pfn;
+
+ /*
+ * scan at the beginning of MAX_ORDER_NR_PAGES aligned range to avoid
+ * only isolating a subset of pageblocks from a bigger than pageblock
+ * free or in-use page. Also make sure all to-be-isolated pageblocks
+ * are within the same zone.
+ */
+ zone = page_zone(pfn_to_page(isolate_pageblock));
+ start_pfn = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES),
+ zone->zone_start_pfn);
+
+ saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
+ set_pageblock_migratetype(pfn_to_page(isolate_pageblock), MIGRATE_ISOLATE);
+
+ /*
+ * Bail out early when the to-be-isolated pageblock does not form
+ * a free or in-use page across boundary_pfn:
+ *
+ * 1. isolate before boundary_pfn: the page after is not online
+ * 2. isolate after boundary_pfn: the page before is not online
+ *
+ * This also ensures correctness. Without it, when isolate after
+ * boundary_pfn and [start_pfn, boundary_pfn) are not online,
+ * __first_valid_page() will return unexpected NULL in the for loop
+ * below.
+ */
+ if (isolate_before) {
+ if (!pfn_to_online_page(boundary_pfn))
+ return 0;
+ } else {
+ if (!pfn_to_online_page(boundary_pfn - 1))
+ return 0;
+ }
+
+ for (pfn = start_pfn; pfn < boundary_pfn;) {
+ struct page *page = __first_valid_page(pfn, boundary_pfn - pfn);
+
+ VM_BUG_ON(!page);
+ pfn = page_to_pfn(page);
+ /*
+ * start_pfn is MAX_ORDER_NR_PAGES aligned, if there is any
+ * free pages in [start_pfn, boundary_pfn), its head page will
+ * always be in the range.
+ */
+ if (PageBuddy(page)) {
+ int order = buddy_order(page);
+
+ if (pfn + (1UL << order) > boundary_pfn)
+ split_free_page(page, order, boundary_pfn - pfn);
+ pfn += (1UL << order);
+ continue;
+ }
+ /*
+ * migrate compound pages then let the free page handling code
+ * above do the rest. If migration is not enabled, just fail.
+ */
+ if (PageHuge(page) || PageTransCompound(page)) {
+#if defined CONFIG_COMPACTION || defined CONFIG_CMA
+ unsigned long nr_pages = compound_nr(page);
+ int order = compound_order(page);
+ struct page *head = compound_head(page);
+ unsigned long head_pfn = page_to_pfn(head);
+ int ret;
+ struct compact_control cc = {
+ .nr_migratepages = 0,
+ .order = -1,
+ .zone = page_zone(pfn_to_page(head_pfn)),
+ .mode = MIGRATE_SYNC,
+ .ignore_skip_hint = true,
+ .no_set_skip_hint = true,
+ .gfp_mask = gfp_flags,
+ .alloc_contig = true,
+ };
+ INIT_LIST_HEAD(&cc.migratepages);
+
+ if (head_pfn + nr_pages < boundary_pfn) {
+ pfn += nr_pages;
+ continue;
+ }
+
+ ret = __alloc_contig_migrate_range(&cc, head_pfn,
+ head_pfn + nr_pages);
+
+ if (ret)
+ goto failed;
+ /*
+ * reset pfn, let the free page handling code above
+ * split the free page to the right migratetype list.
+ *
+ * head_pfn is not used here as a hugetlb page order
+ * can be bigger than MAX_ORDER-1, but after it is
+ * freed, the free page order is not. Use pfn within
+ * the range to find the head of the free page and
+ * reset order to 0 if a hugetlb page with
+ * >MAX_ORDER-1 order is encountered.
+ */
+ if (order > MAX_ORDER-1)
+ order = 0;
+ while (!PageBuddy(pfn_to_page(pfn))) {
+ order++;
+ pfn &= ~0UL << order;
+ }
+ continue;
+#else
+ goto failed;
+#endif
+ }
+
+ pfn++;
+ }
+ return 0;
+failed:
+ /* restore the original migratetype */
+ set_pageblock_migratetype(pfn_to_page(isolate_pageblock), saved_mt);
+ return -EBUSY;
+}
+
+/**
* start_isolate_page_range() - make page-allocation-type of range of pages to
* be MIGRATE_ISOLATE.
* @start_pfn: The lower PFN of the range to be isolated.
@@ -293,6 +444,8 @@ __first_valid_page(unsigned long pfn, un
* and PageOffline() pages.
* REPORT_FAILURE - report details about the failure to
* isolate the range
+ * @gfp_flags: GFP flags used for migrating pages that sit across the
+ * range boundaries.
*
* Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
* the range will never be allocated. Any free pages and pages freed in the
@@ -301,6 +454,10 @@ __first_valid_page(unsigned long pfn, un
* pages in the range finally, the caller have to free all pages in the range.
* test_page_isolated() can be used for test it.
*
+ * The function first tries to isolate the pageblocks at the beginning and end
+ * of the range, since there might be pages across the range boundaries.
+ * Afterwards, it isolates the rest of the range.
+ *
* There is no high level synchronization mechanism that prevents two threads
* from trying to isolate overlapping ranges. If this happens, one thread
* will notice pageblocks in the overlapping range already set to isolate.
@@ -321,21 +478,38 @@ __first_valid_page(unsigned long pfn, un
* Return: 0 on success and -EBUSY if any part of range cannot be isolated.
*/
int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
- unsigned migratetype, int flags)
+ int migratetype, int flags, gfp_t gfp_flags)
{
unsigned long pfn;
struct page *page;
+ int ret;
BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
- for (pfn = start_pfn;
- pfn < end_pfn;
+ /* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */
+ ret = isolate_single_pageblock(start_pfn, gfp_flags, false);
+ if (ret)
+ return ret;
+
+ /* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */
+ ret = isolate_single_pageblock(end_pfn, gfp_flags, true);
+ if (ret) {
+ unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype);
+ return ret;
+ }
+
+ /* skip isolated pageblocks at the beginning and end */
+ for (pfn = start_pfn + pageblock_nr_pages;
+ pfn < end_pfn - pageblock_nr_pages;
pfn += pageblock_nr_pages) {
page = __first_valid_page(pfn, pageblock_nr_pages);
if (page && set_migratetype_isolate(page, migratetype, flags,
start_pfn, end_pfn)) {
undo_isolate_page_range(start_pfn, pfn, migratetype);
+ unset_migratetype_isolate(
+ pfn_to_page(end_pfn - pageblock_nr_pages),
+ migratetype);
return -EBUSY;
}
}
@@ -346,7 +520,7 @@ int start_isolate_page_range(unsigned lo
* Make isolated pages available again.
*/
void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
- unsigned migratetype)
+ int migratetype)
{
unsigned long pfn;
struct page *page;
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-page_alloc-simplify-pageblock-migratetype-check-in-__free_one_page.patch
mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation.patch
mm-wrap-__find_buddy_pfn-with-a-necessary-buddy-page-validation-v4.patch
mm-page_isolation-move-has_unmovable_pages-to-mm-page_isolationc.patch
mm-page_isolation-check-specified-range-for-unmovable-pages.patch
mm-make-alloc_contig_range-work-at-pageblock-granularity.patch
mm-page_isolation-enable-arbitrary-range-page-isolation.patch
mm-cma-use-pageblock_order-as-the-single-alignment.patch
drivers-virtio_mem-use-pageblock-size-as-the-minimum-virtio_mem-size.patch
