The quilt patch titled
Subject: mm/page_ext: do not allocate space for page_ext->flags if not needed
has been removed from the -mm tree. Its filename was
mm-page_ext-do-not-allocate-space-for-page_ext-flags-if-not-needed.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Subject: mm/page_ext: do not allocate space for page_ext->flags if not needed
Date: Fri, 13 Jan 2023 15:42:53 +0000
There is 8 byte page_ext->flags field allocated per page whenever
CONFIG_PAGE_EXTENSION is enabled. However, not every user of page_ext
uses flags. Therefore, check whether flags is needed at least by one user
and if so allocate space for it.
For example when page_table_check is enabled, on a machine with 128G
of memory before the fix:
[ 2.244288] allocated 536870912 bytes of page_ext
after the fix:
[ 2.160154] allocated 268435456 bytes of page_ext
Also, add a kernel-doc comment before page_ext_operations that describes
the fields, and remove check if need() is set, as that is now a required
field.
[pasha.tatashin@xxxxxxxxxx: address comments from Mike Rapoport]
Link: https://lkml.kernel.org/r/20230117202103.1412449-1-pasha.tatashin@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20230113154253.92480-1-pasha.tatashin@xxxxxxxxxx
Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Reviewed-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Charan Teja Kalla <quic_charante@xxxxxxxxxxx>
Cc: Li Zhe <lizhe.67@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/page_ext.h~mm-page_ext-do-not-allocate-space-for-page_ext-flags-if-not-needed
+++ a/include/linux/page_ext.h
@@ -7,15 +7,33 @@
#include <linux/stackdepot.h>
struct pglist_data;
+
+/**
+ * struct page_ext_operations - per page_ext client operations
+ * @offset: Offset to the client's data within page_ext. Offset is returned to
+ * the client by page_ext_init.
+ * @size: The size of the client data within page_ext.
+ * @need: Function that returns true if client requires page_ext.
+ * @init: (optional) Called to initialize client once page_exts are allocated.
+ * @need_shared_flags: True when client is using shared page_ext->flags
+ * field.
+ *
+ * Each Page Extension client must define page_ext_operations in
+ * page_ext_ops array.
+ */
struct page_ext_operations {
size_t offset;
size_t size;
bool (*need)(void);
void (*init)(void);
+ bool need_shared_flags;
};
#ifdef CONFIG_PAGE_EXTENSION
+/*
+ * The page_ext_flags users must set need_shared_flags to true.
+ */
enum page_ext_flags {
PAGE_EXT_OWNER,
PAGE_EXT_OWNER_ALLOCATED,
--- a/mm/page_ext.c~mm-page_ext-do-not-allocate-space-for-page_ext-flags-if-not-needed
+++ a/mm/page_ext.c
@@ -71,6 +71,7 @@ static bool need_page_idle(void)
}
static struct page_ext_operations page_idle_ops __initdata = {
.need = need_page_idle,
+ .need_shared_flags = true,
};
#endif
@@ -86,7 +87,7 @@ static struct page_ext_operations *page_
#endif
};
-unsigned long page_ext_size = sizeof(struct page_ext);
+unsigned long page_ext_size;
static unsigned long total_usage;
static struct page_ext *lookup_page_ext(const struct page *page);
@@ -106,7 +107,16 @@ static bool __init invoke_need_callbacks
bool need = false;
for (i = 0; i < entries; i++) {
- if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
+ if (page_ext_ops[i]->need()) {
+ if (page_ext_ops[i]->need_shared_flags) {
+ page_ext_size = sizeof(struct page_ext);
+ break;
+ }
+ }
+ }
+
+ for (i = 0; i < entries; i++) {
+ if (page_ext_ops[i]->need()) {
page_ext_ops[i]->offset = page_ext_size;
page_ext_size += page_ext_ops[i]->size;
need = true;
--- a/mm/page_owner.c~mm-page_ext-do-not-allocate-space-for-page_ext-flags-if-not-needed
+++ a/mm/page_owner.c
@@ -99,6 +99,7 @@ struct page_ext_operations page_owner_op
.size = sizeof(struct page_owner),
.need = need_page_owner,
.init = init_page_owner,
+ .need_shared_flags = true,
};
static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
--- a/mm/page_table_check.c~mm-page_ext-do-not-allocate-space-for-page_ext-flags-if-not-needed
+++ a/mm/page_table_check.c
@@ -45,6 +45,7 @@ struct page_ext_operations page_table_ch
.size = sizeof(struct page_table_check),
.need = need_page_table_check,
.init = init_page_table_check,
+ .need_shared_flags = false,
};
static struct page_table_check *get_page_table_check(struct page_ext *page_ext)
_
Patches currently in -mm which might be from pasha.tatashin@xxxxxxxxxx are
