Commit 6189eb82 authored by Pasha Tatashin's avatar Pasha Tatashin Committed by Andrew Morton
Browse files

mm/page_ext: do not allocate space for page_ext->flags if not needed 

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@soleen.com: address comments from Mike Rapoport]
  Link: https://lkml.kernel.org/r/20230117202103.1412449-1-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20230113154253.92480-1-pasha.tatashin@soleen.com


Signed-off-by: default avatarPasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Reviewed-by: default avatarMike Rapoport (IBM) <rppt@kernel.org>
Cc: Charan Teja Kalla <quic_charante@quicinc.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 950fe885

include/linux/page_ext.h

+18 −0
Original line number Diff line number Diff line
@@ -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,

mm/page_ext.c

+12 −2
Original line number Diff line number Diff line
@@ -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_ext_ops[] __initdata = { 
#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(void) 
	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;

mm/page_owner.c

+1 −0
Original line number Diff line number Diff line
@@ -99,6 +99,7 @@ struct page_ext_operations page_owner_ops = { 
	.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)

mm/page_table_check.c

+1 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ struct page_ext_operations page_table_check_ops = { 
	.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)