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Date: Wed, 8 Mar 2023 11:41:04 +0200
From: Mike Rapoport <rppt@...nel.org>
To: linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Mike Rapoport <rppt@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Song Liu <song@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
x86@...nel.org
Subject: [RFC PATCH 3/5] mm/unmapped_alloc: add shrinker
From: "Mike Rapoport (IBM)" <rppt@...nel.org>
Allow shrinking unmapped caches when there is a memory pressure.
Signed-off-by: Mike Rapoport(IBM) <rppt@...nel.org>
---
mm/internal.h | 2 ++
mm/page_alloc.c | 12 ++++++-
mm/unmapped-alloc.c | 86 ++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 98 insertions(+), 2 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 8d84cceab467..aa2934594dcf 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1064,4 +1064,6 @@ static inline struct page *unmapped_pages_alloc(gfp_t gfp, int order)
static inline void unmapped_pages_free(struct page *page, int order) {}
#endif
+void __free_unmapped_page(struct page *page, unsigned int order);
+
#endif /* __MM_INTERNAL_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 01f18e7529b0..ece213fac27a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -123,6 +123,11 @@ typedef int __bitwise fpi_t;
*/
#define FPI_SKIP_KASAN_POISON ((__force fpi_t)BIT(2))
+/*
+ * Free pages from the unmapped cache
+ */
+#define FPI_UNMAPPED ((__force fpi_t)BIT(3))
+
/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
static DEFINE_MUTEX(pcp_batch_high_lock);
#define MIN_PERCPU_PAGELIST_HIGH_FRACTION (8)
@@ -1467,7 +1472,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
PAGE_SIZE << order);
}
- if (get_pageblock_unmapped(page)) {
+ if (!(fpi_flags & FPI_UNMAPPED) && get_pageblock_unmapped(page)) {
unmapped_pages_free(page, order);
return false;
}
@@ -1636,6 +1641,11 @@ static void free_one_page(struct zone *zone,
spin_unlock_irqrestore(&zone->lock, flags);
}
+void __free_unmapped_page(struct page *page, unsigned int order)
+{
+ __free_pages_ok(page, order, FPI_UNMAPPED | FPI_TO_TAIL);
+}
+
static void __meminit __init_single_page(struct page *page, unsigned long pfn,
unsigned long zone, int nid)
{
diff --git a/mm/unmapped-alloc.c b/mm/unmapped-alloc.c
index f74640e9ce9f..89f54383df92 100644
--- a/mm/unmapped-alloc.c
+++ b/mm/unmapped-alloc.c
@@ -4,6 +4,7 @@
#include <linux/mmzone.h>
#include <linux/printk.h>
#include <linux/debugfs.h>
+#include <linux/shrinker.h>
#include <linux/spinlock.h>
#include <linux/set_memory.h>
@@ -16,6 +17,7 @@ struct unmapped_free_area {
spinlock_t lock;
unsigned long nr_free;
unsigned long nr_cached;
+ unsigned long nr_released;
};
static struct unmapped_free_area free_area[MAX_ORDER];
@@ -204,6 +206,82 @@ void unmapped_pages_free(struct page *page, int order)
__free_one_page(page, order, false);
}
+static unsigned long unmapped_alloc_count_objects(struct shrinker *sh,
+ struct shrink_control *sc)
+{
+ unsigned long pages_to_free = 0;
+
+ for (int order = 0; order < MAX_ORDER; order++)
+ pages_to_free += (free_area[order].nr_free << order);
+
+ return pages_to_free;
+}
+
+static unsigned long scan_free_area(struct shrink_control *sc, int order)
+{
+ struct unmapped_free_area *area = &free_area[order];
+ unsigned long nr_pages = (1 << order);
+ unsigned long pages_freed = 0;
+ unsigned long flags;
+ struct page *page;
+
+ spin_lock_irqsave(&area->lock, flags);
+ while (pages_freed < sc->nr_to_scan) {
+
+ page = list_first_entry_or_null(&area->free_list, struct page,
+ lru);
+ if (!page)
+ break;
+
+ del_page_from_free_list(page, order);
+ expand(page, order, order);
+
+ area->nr_released++;
+
+ if (order == pageblock_order)
+ clear_pageblock_unmapped(page);
+
+ spin_unlock_irqrestore(&area->lock, flags);
+
+ for (int i = 0; i < nr_pages; i++)
+ set_direct_map_default_noflush(page + i);
+
+ __free_unmapped_page(page, order);
+
+ pages_freed += nr_pages;
+
+ cond_resched();
+ spin_lock_irqsave(&area->lock, flags);
+ }
+
+ spin_unlock_irqrestore(&area->lock, flags);
+
+ return pages_freed;
+}
+
+static unsigned long unmapped_alloc_scan_objects(struct shrinker *shrinker,
+ struct shrink_control *sc)
+{
+ sc->nr_scanned = 0;
+
+ for (int order = 0; order < MAX_ORDER; order++) {
+ sc->nr_scanned += scan_free_area(sc, order);
+
+ if (sc->nr_scanned >= sc->nr_to_scan)
+ break;
+
+ sc->nr_to_scan -= sc->nr_scanned;
+ }
+
+ return sc->nr_scanned ? sc->nr_scanned : SHRINK_STOP;
+}
+
+static struct shrinker shrinker = {
+ .count_objects = unmapped_alloc_count_objects,
+ .scan_objects = unmapped_alloc_scan_objects,
+ .seeks = DEFAULT_SEEKS,
+};
+
int unmapped_alloc_init(void)
{
for (int order = 0; order < MAX_ORDER; order++) {
@@ -237,6 +315,11 @@ static int unmapped_alloc_debug_show(struct seq_file *m, void *private)
seq_printf(m, "%5lu ", free_area[order].nr_cached);
seq_putc(m, '\n');
+ seq_printf(m, "%-10s", "Released:");
+ for (order = 0; order < MAX_ORDER; ++order)
+ seq_printf(m, "%5lu ", free_area[order].nr_released);
+ seq_putc(m, '\n');
+
return 0;
}
DEFINE_SHOW_ATTRIBUTE(unmapped_alloc_debug);
@@ -245,6 +328,7 @@ static int __init unmapped_alloc_init_late(void)
{
debugfs_create_file("unmapped_alloc", 0444, NULL,
NULL, &unmapped_alloc_debug_fops);
- return 0;
+
+ return register_shrinker(&shrinker, "mm-unmapped-alloc");
}
late_initcall(unmapped_alloc_init_late);
--
2.35.1
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