[PATCH v6 0/1] mm: report per-page metadata information

[PATCH v6 0/1] mm: report per-page metadata information

[Sourav Panda]

Changelog:
v6:
	- Interface changes
	  	- Added per-node nr_page_metadata and
		  nr_page_metadata_boot fields that are exported
		  in /sys/devices/system/node/nodeN/vmstat
		- nr_page_metadata exclusively tracks buddy
		  allocations while nr_page_metadata_boot
		  exclusively tracks memblock allocations.
		- Modified PageMetadata in /proc/meminfo to only
		  include buddy allocations so that it is
		  comparable against MemTotal in /proc/meminfo
		- Removed the PageMetadata field added in
		  /sys/devices/system/node/nodeN/meminfo
	- Addressed bugs reported by the kernel test bot.
	  	- All occurences of __mod_node_page_state have
		  been replaced by mod_node_page_state.
	- Addressed comments from Muchun Song.
	  	- Removed page meta data accouting from
		  mm/hugetlb.c. When CONFIG_SPARSEMEM_VMEMMAP
		  is disabled struct pages should not be returned
		  to buddy.
	- Modified the cover letter with the results and analysis
		- From when memory_hotplug.memmap_on_memory is
		  alternated between 0 and 1.
		- To account for the new interface changes.

v5:
	- Addressed comments from Muchun Song.
		- Fixed errors introduced in v4 when
		  CONFIG_SPARSEMEM_VMEMMAP is disabled by testing
		  against FLATMEM and SPARSEMEM memory models.
		- Handled the condition wherein the allocation of
		  walk.reuse_page fails, by moving NR_PAGE_METADATA
		  update into the clause if( walk.reuse_page ).
		- Removed the usage of DIV_ROUND_UP from
		  alloc_vmemmap_page_list since "end - start" is
		  always a multiple of PAGE_SIZE.
		- Modified alloc_vmemmap_page_list to update
		  NR_PAGE_METADATA once instead of every loop.
v4:
	- Addressed comment from Matthew Wilcox.
		- Used __node_stat_sub_folio and __node_stat_add_folio
		  instead of __mod_node_page_state in mm/hugetlb.c.
		- Used page_pgdat wherever possible in the entire patch.
		- Used DIV_ROUND_UP() wherever possible in the entire
		  patch.
v3:
	- Addressed one comment from Matthew Wilcox.
	  	- In free_page_ext, page_pgdat() is now extracted
		  prior to freeing the memory.
v2:
	- Fixed the three bugs reported by kernel test robot.
	- Enhanced the commit message as recommended by David Hildenbrand.
	- Addressed comments from Matthew Wilcox:
	  	- Simplified alloc_vmemmap_page_list() and
		  free_page_ext() as recommended.
		- Used the appropriate comment style in mm/vmstat.c.
		- Replaced writeout_early_perpage_metadata() with
		  store_early_perpage_metadata() to reduce ambiguity
		  with what swap does.
	- Addressed comments from Mike Rapoport:
	  	- Simplified the loop in alloc_vmemmap_page_list().
		- Could NOT address a comment to move
		  store_early_perpage_metadata() near where nodes
		  and page allocator are initialized.
		- Included the vmalloc()ed page_ext in accounting
		  within free_page_ext().
		- Made early_perpage_metadata[MAX_NUMNODES] static.


Previous approaches and discussions
-----------------------------------
v5:
https://lore.kernel.org/all/20231101230816.1459373-1-souravpanda@google.com
v4:
https://lore.kernel.org/all/20231031223846.827173-1-souravpanda@google.com
v3:
https://lore.kernel.org/all/20231031174459.459480-1-souravpanda@google.com
v2:
https://lore.kernel.org/all/20231018005548.3505662-1-souravpanda@google.com
v1:
https://lore.kernel.org/r/20230913173000.4016218-2-souravpanda@google.com

Hi!

This patch adds two new per-node fields, namely nr_page_metadata and
nr_page_metadata_boot to /sys/devices/system/node/nodeN/vmstat and a
global PageMetadata field to /proc/meminfo. This information can be
used by users to see how much memory is being used by per-page
metadata, which can vary depending on build configuration, machine
architecture, and system use.

Per-page metadata is the amount of memory that Linux needs in order to
manage memory at the page granularity. The majority of such memory is
used by "struct page" and "page_ext" data structures.


Background
----------

Kernel overhead observability is missing some of the largest
allocations during runtime, including vmemmap (struct pages) and
page_ext. This patch aims to address this problem by exporting a
new metric PageMetadata.

On the contrary, the kernel does provide observibility for boot memory
allocations. For example, the metric reserved_pages depicts the pages
allocated by the bootmem allocator. This can be simply calculated as
present_pages - managed_pages, which are both exported in /proc/zoneinfo.
The metric reserved_pages is primarily composed of struct pages and
page_ext.

What about the struct pages (allocated by bootmem allocator) that are
free'd during hugetlbfs allocations and then allocated by buddy-allocator
once hugtlbfs pages are free'd?

/proc/meminfo MemTotal changes: MemTotal does not include memblock
allocations but includes buddy allocations. However, during runtime
memblock allocations can be shifted into buddy allocations, and therefore
become part of MemTotal.

Once the struct pages get allocated by buddy allocator, we lose track of
these struct page allocations overhead accounting. Therefore, we must
export new metrics. nr_page_metadata and nr_page_metadata_boot
exclusively track the struct page and page ext allocations made by the
buddy allocator and memblock allocator, respectively for each node.
PageMetadata in /proc/meminfo would report the struct page and page ext
allocations made by the buddy allocator.

Results and analysis
--------------------

Memory model: Sparsemem-vmemmap
$ echo 1 > /proc/sys/vm/hugetlb_optimize_vmemmap

$ cat /proc/meminfo | grep MemTotal
	MemTotal:       32919124 kB
$ cat /proc/meminfo | grep Meta
	PageMetadata:      65536 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
        nr_page_metadata 8192
	nr_page_metadata_boot 65536

AFTER HUGTLBFS RESERVATION
$ echo 512 > /proc/sys/vm/nr_hugepages

$ cat /proc/meminfo | grep MemTotal
	MemTotal:       32935508 kB
$ cat /proc/meminfo | grep Meta
	PageMetadata:      67584 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8448
	nr_page_metadata_boot 63488
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8448
	nr_page_metadata_booy 63488


AFTER FREEING HUGTLBFS RESERVATION
$ echo 0 > /proc/sys/vm/nr_hugepages

$ cat /proc/meminfo | grep MemTotal
        MemTotal:       32935508 kB
$ cat /proc/meminfo | grep Meta
        PageMetadata:      81920 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
        nr_page_metadata 10240
	nr_page_metadata_boot 63488
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
        nr_page_metadata 10240
	nr_page_metadata_boot 63488

------------------------

Memory Hotplug with memory_hotplug.memmap_on_memory=1

BEFORE HOTADD
$ cat /proc/meminfo | grep MemTotal
	MemTotal:       32919124 kB
$ cat /proc/meminfo | grep PageMeta
	PageMetadata:      65536 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536

AFTER HOTADDING 1GB
$ cat /proc/meminfo | grep MemTotal
	MemTotal:       33951316 kB
$ cat /proc/meminfo | grep PageMeta
	PageMetadata:      83968 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
	nr_page_metadata 12800
	nr_page_metadata_boot 65536
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536

--------------------------

Memory Hotplug with memory_hotplug.memmap_on_memory=0

BEFORE HOTADD
$ cat /proc/meminfo | grep MemTotal
	MemTotal:       32919124 kB
$ cat /proc/meminfo | grep PageMeta
	PageMetadata:      65536 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536

AFTER HOTADDING 1GB
$ cat /proc/meminfo | grep MemTotal
	MemTotal:       33967700 kB
$ cat /proc/meminfo | grep PageMeta
	PageMetadata:      83968 kB
$ cat /sys/devices/system/node/node0/vmstat | grep "nr_page_metadata"
	nr_page_metadata 12800
	nr_page_metadata_boot 65536
$ cat /sys/devices/system/node/node1/vmstat | grep "nr_page_metadata"
	nr_page_metadata 8192
	nr_page_metadata_boot 65536

Sourav Panda (1):
  mm: report per-page metadata information

 Documentation/filesystems/proc.rst |  3 +++
 fs/proc/meminfo.c                  |  7 +++++++
 include/linux/mmzone.h             |  4 ++++
 include/linux/vmstat.h             |  4 ++++
 mm/hugetlb_vmemmap.c               | 19 ++++++++++++++----
 mm/mm_init.c                       |  3 +++
 mm/page_alloc.c                    |  1 +
 mm/page_ext.c                      | 32 +++++++++++++++++++++---------
 mm/sparse-vmemmap.c                |  8 ++++++++
 mm/sparse.c                        |  7 ++++++-
 mm/vmstat.c                        | 26 +++++++++++++++++++++++-
 11 files changed, 99 insertions(+), 15 deletions(-)

-- 
2.43.0.472.g3155946c3a-goog

[PATCH v6 1/1] mm: report per-page metadata information

[Sourav Panda]

Adds two new per-node fields, namely nr_page_metadata and
nr_page_metadata_boot, to /sys/devices/system/node/nodeN/vmstat
and a global PageMetadata field to /proc/meminfo. This information can
be used by users to see how much memory is being used by per-page
metadata, which can vary depending on build configuration, machine
architecture, and system use.

Per-page metadata is the amount of memory that Linux needs in order to
manage memory at the page granularity. The majority of such memory is
used by "struct page" and "page_ext" data structures. In contrast to
most other memory consumption statistics, per-page metadata might not
be included in MemTotal. For example, MemTotal does not include memblock
allocations but includes buddy allocations. In this patch, exported
field nr_page_metadata in /sys/devices/system/node/nodeN/vmstat would
exclusively track buddy allocations while nr_page_metadata_boot would
exclusively track memblock allocations. Furthermore, PageMetadata in
/proc/meminfo would exclusively track buddy allocations allowing it to
be compared against MemTotal.

This memory depends on build configurations, machine architectures, and
the way system is used:

Build configuration may include extra fields into "struct page",
and enable / disable "page_ext"
Machine architecture defines base page sizes. For example 4K x86,
8K SPARC, 64K ARM64 (optionally), etc. The per-page metadata
overhead is smaller on machines with larger page sizes.
System use can change per-page overhead by using vmemmap
optimizations with hugetlb pages, and emulated pmem devdax pages.
Also, boot parameters can determine whether page_ext is needed
to be allocated. This memory can be part of MemTotal or be outside
MemTotal depending on whether the memory was hot-plugged, booted with,
or hugetlb memory was returned back to the system.

Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Sourav Panda <souravpanda@google.com>
---
 Documentation/filesystems/proc.rst |  3 +++
 fs/proc/meminfo.c                  |  7 +++++++
 include/linux/mmzone.h             |  4 ++++
 include/linux/vmstat.h             |  4 ++++
 mm/hugetlb_vmemmap.c               | 19 ++++++++++++++----
 mm/mm_init.c                       |  3 +++
 mm/page_alloc.c                    |  1 +
 mm/page_ext.c                      | 32 +++++++++++++++++++++---------
 mm/sparse-vmemmap.c                |  8 ++++++++
 mm/sparse.c                        |  7 ++++++-
 mm/vmstat.c                        | 26 +++++++++++++++++++++++-
 11 files changed, 99 insertions(+), 15 deletions(-)

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 49ef12df631b..d5901d04e082 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -993,6 +993,7 @@ Example output. You may not have all of these fields.
     AnonPages:       4654780 kB
     Mapped:           266244 kB
     Shmem:              9976 kB
+    PageMetadata:     513419 kB
     KReclaimable:     517708 kB
     Slab:             660044 kB
     SReclaimable:     517708 kB
@@ -1095,6 +1096,8 @@ Mapped
               files which have been mmapped, such as libraries
 Shmem
               Total memory used by shared memory (shmem) and tmpfs
+PageMetadata
+              Memory used for per-page metadata
 KReclaimable
               Kernel allocations that the kernel will attempt to reclaim
               under memory pressure. Includes SReclaimable (below), and other
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 45af9a989d40..f141bb2a550d 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -39,7 +39,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	long available;
 	unsigned long pages[NR_LRU_LISTS];
 	unsigned long sreclaimable, sunreclaim;
+	unsigned long nr_page_metadata;
 	int lru;
+	int nid;
 
 	si_meminfo(&i);
 	si_swapinfo(&i);
@@ -57,6 +59,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	sreclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B);
 	sunreclaim = global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B);
 
+	nr_page_metadata = 0;
+	for_each_online_node(nid)
+		nr_page_metadata += node_page_state(NODE_DATA(nid), NR_PAGE_METADATA);
+
 	show_val_kb(m, "MemTotal:       ", i.totalram);
 	show_val_kb(m, "MemFree:        ", i.freeram);
 	show_val_kb(m, "MemAvailable:   ", available);
@@ -104,6 +110,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "Mapped:         ",
 		    global_node_page_state(NR_FILE_MAPPED));
 	show_val_kb(m, "Shmem:          ", i.sharedram);
+	show_val_kb(m, "PageMetadata:   ", nr_page_metadata);
 	show_val_kb(m, "KReclaimable:   ", sreclaimable +
 		    global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE));
 	show_val_kb(m, "Slab:           ", sreclaimable + sunreclaim);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3c25226beeed..ef176152be7c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -207,6 +207,10 @@ enum node_stat_item {
 	PGPROMOTE_SUCCESS,	/* promote successfully */
 	PGPROMOTE_CANDIDATE,	/* candidate pages to promote */
 #endif
+	NR_PAGE_METADATA,	/* Page metadata size (struct page and page_ext)
+				 * in pages
+				 */
+	NR_PAGE_METADATA_BOOT,	/* NR_PAGE_METADATA for bootmem */
 	NR_VM_NODE_STAT_ITEMS
 };
 
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index fed855bae6d8..af096a881f03 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -656,4 +656,8 @@ static inline void lruvec_stat_sub_folio(struct folio *folio,
 {
 	lruvec_stat_mod_folio(folio, idx, -folio_nr_pages(folio));
 }
+
+void __init mod_node_early_perpage_metadata(int nid, long delta);
+void __init store_early_perpage_metadata(void);
+
 #endif /* _LINUX_VMSTAT_H */
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 87818ee7f01d..5b10d8d2b471 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -230,10 +230,14 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
  */
 static inline void free_vmemmap_page(struct page *page)
 {
-	if (PageReserved(page))
+	if (PageReserved(page)) {
 		free_bootmem_page(page);
-	else
+		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA_BOOT,
+				    -1);
+	} else {
 		__free_page(page);
+		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA, -1);
+	}
 }
 
 /* Free a list of the vmemmap pages */
@@ -389,6 +393,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
 		copy_page(page_to_virt(walk.reuse_page),
 			  (void *)walk.reuse_addr);
 		list_add(&walk.reuse_page->lru, vmemmap_pages);
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, 1);
 	}
 
 	/*
@@ -437,14 +442,20 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
 	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
 	int nid = page_to_nid((struct page *)start);
 	struct page *page, *next;
+	int i;
 
-	while (nr_pages--) {
+	for (i = 0; i < nr_pages; i++) {
 		page = alloc_pages_node(nid, gfp_mask, 0);
-		if (!page)
+		if (!page) {
+			mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
+					    i);
 			goto out;
+		}
 		list_add(&page->lru, list);
 	}
 
+	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, nr_pages);
+
 	return 0;
 out:
 	list_for_each_entry_safe(page, next, list, lru)
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 077bfe393b5e..38f8e1f454a0 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -26,6 +26,7 @@
 #include <linux/pgtable.h>
 #include <linux/swap.h>
 #include <linux/cma.h>
+#include <linux/vmstat.h>
 #include "internal.h"
 #include "slab.h"
 #include "shuffle.h"
@@ -1656,6 +1657,8 @@ static void __init alloc_node_mem_map(struct pglist_data *pgdat)
 			panic("Failed to allocate %ld bytes for node %d memory map\n",
 			      size, pgdat->node_id);
 		pgdat->node_mem_map = map + offset;
+		mod_node_early_perpage_metadata(pgdat->node_id,
+						DIV_ROUND_UP(size, PAGE_SIZE));
 	}
 	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
 				__func__, pgdat->node_id, (unsigned long)pgdat,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 733732e7e0ba..dd78017105b0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5636,6 +5636,7 @@ void __init setup_per_cpu_pageset(void)
 	for_each_online_pgdat(pgdat)
 		pgdat->per_cpu_nodestats =
 			alloc_percpu(struct per_cpu_nodestat);
+	store_early_perpage_metadata();
 }
 
 __meminit void zone_pcp_init(struct zone *zone)
diff --git a/mm/page_ext.c b/mm/page_ext.c
index 4548fcc66d74..4ca9f298f34e 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -201,6 +201,8 @@ static int __init alloc_node_page_ext(int nid)
 		return -ENOMEM;
 	NODE_DATA(nid)->node_page_ext = base;
 	total_usage += table_size;
+	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
+			    DIV_ROUND_UP(table_size, PAGE_SIZE));
 	return 0;
 }
 
@@ -255,12 +257,15 @@ static void *__meminit alloc_page_ext(size_t size, int nid)
 	void *addr = NULL;
 
 	addr = alloc_pages_exact_nid(nid, size, flags);
-	if (addr) {
+	if (addr)
 		kmemleak_alloc(addr, size, 1, flags);
-		return addr;
-	}
+	else
+		addr = vzalloc_node(size, nid);
 
-	addr = vzalloc_node(size, nid);
+	if (addr) {
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
+				    DIV_ROUND_UP(size, PAGE_SIZE));
+	}
 
 	return addr;
 }
@@ -303,18 +308,27 @@ static int __meminit init_section_page_ext(unsigned long pfn, int nid)
 
 static void free_page_ext(void *addr)
 {
+	size_t table_size;
+	struct page *page;
+	struct pglist_data *pgdat;
+
+	table_size = page_ext_size * PAGES_PER_SECTION;
+
 	if (is_vmalloc_addr(addr)) {
+		page = vmalloc_to_page(addr);
+		pgdat = page_pgdat(page);
 		vfree(addr);
 	} else {
-		struct page *page = virt_to_page(addr);
-		size_t table_size;
-
-		table_size = page_ext_size * PAGES_PER_SECTION;
-
+		page = virt_to_page(addr);
+		pgdat = page_pgdat(page);
 		BUG_ON(PageReserved(page));
 		kmemleak_free(addr);
 		free_pages_exact(addr, table_size);
 	}
+
+	mod_node_page_state(pgdat, NR_PAGE_METADATA,
+			    -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
+
 }
 
 static void __free_page_ext(unsigned long pfn)
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index a2cbe44c48e1..054b49539843 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -469,5 +469,13 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn,
 	if (r < 0)
 		return NULL;
 
+	if (system_state == SYSTEM_BOOTING) {
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
+				    DIV_ROUND_UP(end - start, PAGE_SIZE));
+	} else {
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
+				    DIV_ROUND_UP(end - start, PAGE_SIZE));
+	}
+
 	return pfn_to_page(pfn);
 }
diff --git a/mm/sparse.c b/mm/sparse.c
index 77d91e565045..0c100ae1cf8b 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -14,7 +14,7 @@
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/bootmem_info.h>
-
+#include <linux/vmstat.h>
 #include "internal.h"
 #include <asm/dma.h>
 
@@ -465,6 +465,9 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
 	 */
 	sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true);
 	sparsemap_buf_end = sparsemap_buf + size;
+#ifndef CONFIG_SPARSEMEM_VMEMMAP
+	mod_node_early_perpage_metadata(nid, DIV_ROUND_UP(size, PAGE_SIZE));
+#endif
 }
 
 static void __init sparse_buffer_fini(void)
@@ -641,6 +644,8 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
 	unsigned long start = (unsigned long) pfn_to_page(pfn);
 	unsigned long end = start + nr_pages * sizeof(struct page);
 
+	mod_node_page_state(page_pgdat(pfn_to_page(pfn)), NR_PAGE_METADATA,
+			    -1L * (DIV_ROUND_UP(end - start, PAGE_SIZE)));
 	vmemmap_free(start, end, altmap);
 }
 static void free_map_bootmem(struct page *memmap)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 359460deb377..23e88d8c21b7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1249,7 +1249,8 @@ const char * const vmstat_text[] = {
 	"pgpromote_success",
 	"pgpromote_candidate",
 #endif
-
+	"nr_page_metadata",
+	"nr_page_metadata_boot",
 	/* enum writeback_stat_item counters */
 	"nr_dirty_threshold",
 	"nr_dirty_background_threshold",
@@ -2278,4 +2279,27 @@ static int __init extfrag_debug_init(void)
 }
 
 module_init(extfrag_debug_init);
+
 #endif
+
+/*
+ * Page metadata size (struct page and page_ext) in pages
+ */
+static unsigned long early_perpage_metadata[MAX_NUMNODES] __initdata;
+
+void __init mod_node_early_perpage_metadata(int nid, long delta)
+{
+	early_perpage_metadata[nid] += delta;
+}
+
+void __init store_early_perpage_metadata(void)
+{
+	int nid;
+	struct pglist_data *pgdat;
+
+	for_each_online_pgdat(pgdat) {
+		nid = pgdat->node_id;
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
+				    early_perpage_metadata[nid]);
+	}
+}
-- 
2.43.0.472.g3155946c3a-goog

Re: [PATCH v6 0/1] mm: report per-page metadata information

[Greg KH]

On Tue, Dec 05, 2023 at 02:31:17PM -0800, Sourav Panda wrote:
> Changelog:
> v6:
> 	- Interface changes
> 	  	- Added per-node nr_page_metadata and
> 		  nr_page_metadata_boot fields that are exported
> 		  in /sys/devices/system/node/nodeN/vmstat

Again, please do not add any new fields to existing sysfs files, that's
not going to work well.  You can add a new sysfs file, that's file, but
do not continue the abuse of the sysfs api in this file.

thanks,

greg k-h

Re: [PATCH v6 0/1] mm: report per-page metadata information

[Pasha Tatashin]

Hi Greg,

Sourav removed the new field from sys/device../nodeN/meminfo as you
requested; however, in nodeN/vmstat fields still get appended, as
there is code that displays every item in zone_stat_item,
node_stat_item without option to opt-out. I mentioned it to you at
LPC.

In my IOMMU [1] series, there are also fields that are added to
node_stat_item that as result are appended to nodeN/vmstat.

Pasha

[1] https://lore.kernel.org/all/20231130201504.2322355-1-pasha.tatashin@soleen.com

On Tue, Dec 5, 2023 at 9:36 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Dec 05, 2023 at 02:31:17PM -0800, Sourav Panda wrote:
> > Changelog:
> > v6:
> >       - Interface changes
> >               - Added per-node nr_page_metadata and
> >                 nr_page_metadata_boot fields that are exported
> >                 in /sys/devices/system/node/nodeN/vmstat
>
> Again, please do not add any new fields to existing sysfs files, that's
> not going to work well.  You can add a new sysfs file, that's file, but
> do not continue the abuse of the sysfs api in this file.
>
> thanks,
>
> greg k-h

Re: [PATCH v6 0/1] mm: report per-page metadata information

[Greg KH]

On Tue, Dec 05, 2023 at 09:57:36PM -0500, Pasha Tatashin wrote:
> Hi Greg,
> 
> Sourav removed the new field from sys/device../nodeN/meminfo as you
> requested; however, in nodeN/vmstat fields still get appended, as
> there is code that displays every item in zone_stat_item,
> node_stat_item without option to opt-out. I mentioned it to you at
> LPC.

Sorry, I thought that was a proc file, not a sysfs file.  Don't grow
that file please, it should not be that way and adding to it will just
cause others to also want to add to it and we end up with the whole proc
file mess...

> In my IOMMU [1] series, there are also fields that are added to
> node_stat_item that as result are appended to nodeN/vmstat.

I missed that, that too shouldn't be done please.

Again, sysfs is "one value per file" for a reason, don't abuse the fact
that we missed this abuse of the rules for that file by adding more
things to it.

thanks,

greg k-h

Re: [PATCH v6 0/1] mm: report per-page metadata information

[Andrew Morton]

On Wed, 6 Dec 2023 12:12:10 +0900 Greg KH <gregkh@linuxfoundation.org> wrote:

> On Tue, Dec 05, 2023 at 09:57:36PM -0500, Pasha Tatashin wrote:
> > Hi Greg,
> > 
> > Sourav removed the new field from sys/device../nodeN/meminfo as you
> > requested; however, in nodeN/vmstat fields still get appended, as
> > there is code that displays every item in zone_stat_item,
> > node_stat_item without option to opt-out. I mentioned it to you at
> > LPC.
> 
> Sorry, I thought that was a proc file, not a sysfs file.  Don't grow
> that file please, it should not be that way and adding to it will just
> cause others to also want to add to it and we end up with the whole proc
> file mess...
> 
> > In my IOMMU [1] series, there are also fields that are added to
> > node_stat_item that as result are appended to nodeN/vmstat.
> 
> I missed that, that too shouldn't be done please.
> 
> Again, sysfs is "one value per file" for a reason, don't abuse the fact
> that we missed this abuse of the rules for that file by adding more
> things to it.

I'm afraid that horse has bolted.

hp2:/usr/src/25> wc /sys/devices/system/node/node0/vmstat 
  61  122 1309 /sys/devices/system/node/node0/vmstat

We're never going to unpick this into 61 separate files so adding new
files at this stage is pointless.

Re: [PATCH v6 0/1] mm: report per-page metadata information

[Greg KH]

On Wed, Dec 06, 2023 at 07:59:13AM -0800, Andrew Morton wrote:
> On Wed, 6 Dec 2023 12:12:10 +0900 Greg KH <gregkh@linuxfoundation.org> wrote:
> 
> > On Tue, Dec 05, 2023 at 09:57:36PM -0500, Pasha Tatashin wrote:
> > > Hi Greg,
> > > 
> > > Sourav removed the new field from sys/device../nodeN/meminfo as you
> > > requested; however, in nodeN/vmstat fields still get appended, as
> > > there is code that displays every item in zone_stat_item,
> > > node_stat_item without option to opt-out. I mentioned it to you at
> > > LPC.
> > 
> > Sorry, I thought that was a proc file, not a sysfs file.  Don't grow
> > that file please, it should not be that way and adding to it will just
> > cause others to also want to add to it and we end up with the whole proc
> > file mess...
> > 
> > > In my IOMMU [1] series, there are also fields that are added to
> > > node_stat_item that as result are appended to nodeN/vmstat.
> > 
> > I missed that, that too shouldn't be done please.
> > 
> > Again, sysfs is "one value per file" for a reason, don't abuse the fact
> > that we missed this abuse of the rules for that file by adding more
> > things to it.
> 
> I'm afraid that horse has bolted.
> 
> hp2:/usr/src/25> wc /sys/devices/system/node/node0/vmstat 
>   61  122 1309 /sys/devices/system/node/node0/vmstat
> 
> We're never going to unpick this into 61 separate files so adding new
> files at this stage is pointless.

But if it keeps growing, it will eventually overflow and start crashing
the kernel and you will then have to do the horrid thing of turning it
into a binary sysfs file.

So I can please ask that no new entries be added to the file please,
let's not keep making things worse.  For new items, just add new files,
don't add to the existing mess.

thanks,

greg k-h

Re: [PATCH v6 1/1] mm: report per-page metadata information

[Pasha Tatashin]

On Tue, Dec 5, 2023 at 5:31 PM Sourav Panda <souravpanda@google.com> wrote:
>
> Adds two new per-node fields, namely nr_page_metadata and
> nr_page_metadata_boot, to /sys/devices/system/node/nodeN/vmstat
> and a global PageMetadata field to /proc/meminfo. This information can
> be used by users to see how much memory is being used by per-page
> metadata, which can vary depending on build configuration, machine
> architecture, and system use.
>
> Per-page metadata is the amount of memory that Linux needs in order to
> manage memory at the page granularity. The majority of such memory is
> used by "struct page" and "page_ext" data structures. In contrast to
> most other memory consumption statistics, per-page metadata might not
> be included in MemTotal. For example, MemTotal does not include memblock
> allocations but includes buddy allocations. In this patch, exported
> field nr_page_metadata in /sys/devices/system/node/nodeN/vmstat would

It is OK to have nr_page_metadata field in nodeN/vmstat based on this
discussion:
https://lore.kernel.org/linux-mm/CA+CK2bB2=raEP8W5GDW_JY7TDvwtSCbkQjvn=SvbjUjPETXZow@mail.gmail.com

> exclusively track buddy allocations while nr_page_metadata_boot would
> exclusively track memblock allocations. Furthermore, PageMetadata in
> /proc/meminfo would exclusively track buddy allocations allowing it to
> be compared against MemTotal.
>
> This memory depends on build configurations, machine architectures, and
> the way system is used:
>
> Build configuration may include extra fields into "struct page",
> and enable / disable "page_ext"
> Machine architecture defines base page sizes. For example 4K x86,
> 8K SPARC, 64K ARM64 (optionally), etc. The per-page metadata
> overhead is smaller on machines with larger page sizes.
> System use can change per-page overhead by using vmemmap
> optimizations with hugetlb pages, and emulated pmem devdax pages.
> Also, boot parameters can determine whether page_ext is needed
> to be allocated. This memory can be part of MemTotal or be outside
> MemTotal depending on whether the memory was hot-plugged, booted with,
> or hugetlb memory was returned back to the system.
>
> Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Sourav Panda <souravpanda@google.com>

Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>

Pasha

Re: [PATCH v6 1/1] mm: report per-page metadata information

[David Rientjes]

On Tue, 5 Dec 2023, Sourav Panda wrote:

> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 49ef12df631b..d5901d04e082 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -993,6 +993,7 @@ Example output. You may not have all of these fields.
>      AnonPages:       4654780 kB
>      Mapped:           266244 kB
>      Shmem:              9976 kB
> +    PageMetadata:     513419 kB
>      KReclaimable:     517708 kB
>      Slab:             660044 kB
>      SReclaimable:     517708 kB
> @@ -1095,6 +1096,8 @@ Mapped
>                files which have been mmapped, such as libraries
>  Shmem
>                Total memory used by shared memory (shmem) and tmpfs
> +PageMetadata
> +              Memory used for per-page metadata
>  KReclaimable
>                Kernel allocations that the kernel will attempt to reclaim
>                under memory pressure. Includes SReclaimable (below), and other
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 45af9a989d40..f141bb2a550d 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -39,7 +39,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	long available;
>  	unsigned long pages[NR_LRU_LISTS];
>  	unsigned long sreclaimable, sunreclaim;
> +	unsigned long nr_page_metadata;

Initialize it here (if we actually need this variable)?

>  	int lru;
> +	int nid;
>  
>  	si_meminfo(&i);
>  	si_swapinfo(&i);
> @@ -57,6 +59,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	sreclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B);
>  	sunreclaim = global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B);
>  
> +	nr_page_metadata = 0;
> +	for_each_online_node(nid)
> +		nr_page_metadata += node_page_state(NODE_DATA(nid), NR_PAGE_METADATA);

Is this intended to be different than 
global_node_page_state_pages(NR_PAGE_METADATA)?  

If so, any hint as to why we want to discount page metadata on offline 
nodes?  We can't make an inference that metadata is always allocated 
locally, memoryless nodes need things like struct page allocated on nodes 
with memory.

So even if a memoryless node is offline, we'd still be including its 
metadata here with the current implementation.

Or maybe I'm missing a subtlety here for why this is not already 
global_node_page_state_pages().

> +
>  	show_val_kb(m, "MemTotal:       ", i.totalram);
>  	show_val_kb(m, "MemFree:        ", i.freeram);
>  	show_val_kb(m, "MemAvailable:   ", available);
> @@ -104,6 +110,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	show_val_kb(m, "Mapped:         ",
>  		    global_node_page_state(NR_FILE_MAPPED));
>  	show_val_kb(m, "Shmem:          ", i.sharedram);
> +	show_val_kb(m, "PageMetadata:   ", nr_page_metadata);
>  	show_val_kb(m, "KReclaimable:   ", sreclaimable +
>  		    global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE));
>  	show_val_kb(m, "Slab:           ", sreclaimable + sunreclaim);
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 3c25226beeed..ef176152be7c 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -207,6 +207,10 @@ enum node_stat_item {
>  	PGPROMOTE_SUCCESS,	/* promote successfully */
>  	PGPROMOTE_CANDIDATE,	/* candidate pages to promote */
>  #endif
> +	NR_PAGE_METADATA,	/* Page metadata size (struct page and page_ext)
> +				 * in pages
> +				 */
> +	NR_PAGE_METADATA_BOOT,	/* NR_PAGE_METADATA for bootmem */

So if some vmemmap pages are freed, then MemTotal could be incremented by 
a portion of NR_PAGE_METADATA_BOOT and then this stat is decremented?  Is 
the goal that the sum of MemTotal + SUM(nr_page_metadata_boot) is always 
constant?

>  	NR_VM_NODE_STAT_ITEMS
>  };
>  
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index fed855bae6d8..af096a881f03 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -656,4 +656,8 @@ static inline void lruvec_stat_sub_folio(struct folio *folio,
>  {
>  	lruvec_stat_mod_folio(folio, idx, -folio_nr_pages(folio));
>  }
> +
> +void __init mod_node_early_perpage_metadata(int nid, long delta);
> +void __init store_early_perpage_metadata(void);
> +
>  #endif /* _LINUX_VMSTAT_H */
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 87818ee7f01d..5b10d8d2b471 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -230,10 +230,14 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
>   */
>  static inline void free_vmemmap_page(struct page *page)
>  {
> -	if (PageReserved(page))
> +	if (PageReserved(page)) {
>  		free_bootmem_page(page);
> -	else
> +		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA_BOOT,
> +				    -1);
> +	} else {
>  		__free_page(page);
> +		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA, -1);
> +	}
>  }
>  
>  /* Free a list of the vmemmap pages */
> @@ -389,6 +393,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
>  		copy_page(page_to_virt(walk.reuse_page),
>  			  (void *)walk.reuse_addr);
>  		list_add(&walk.reuse_page->lru, vmemmap_pages);
> +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, 1);
>  	}
>  
>  	/*
> @@ -437,14 +442,20 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
>  	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
>  	int nid = page_to_nid((struct page *)start);
>  	struct page *page, *next;
> +	int i;
>  
> -	while (nr_pages--) {
> +	for (i = 0; i < nr_pages; i++) {
>  		page = alloc_pages_node(nid, gfp_mask, 0);
> -		if (!page)
> +		if (!page) {
> +			mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> +					    i);
>  			goto out;
> +		}
>  		list_add(&page->lru, list);
>  	}
>  
> +	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, nr_pages);
> +
>  	return 0;
>  out:
>  	list_for_each_entry_safe(page, next, list, lru)
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 077bfe393b5e..38f8e1f454a0 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -26,6 +26,7 @@
>  #include <linux/pgtable.h>
>  #include <linux/swap.h>
>  #include <linux/cma.h>
> +#include <linux/vmstat.h>
>  #include "internal.h"
>  #include "slab.h"
>  #include "shuffle.h"
> @@ -1656,6 +1657,8 @@ static void __init alloc_node_mem_map(struct pglist_data *pgdat)
>  			panic("Failed to allocate %ld bytes for node %d memory map\n",
>  			      size, pgdat->node_id);
>  		pgdat->node_mem_map = map + offset;
> +		mod_node_early_perpage_metadata(pgdat->node_id,
> +						DIV_ROUND_UP(size, PAGE_SIZE));
>  	}
>  	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
>  				__func__, pgdat->node_id, (unsigned long)pgdat,
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 733732e7e0ba..dd78017105b0 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5636,6 +5636,7 @@ void __init setup_per_cpu_pageset(void)
>  	for_each_online_pgdat(pgdat)
>  		pgdat->per_cpu_nodestats =
>  			alloc_percpu(struct per_cpu_nodestat);
> +	store_early_perpage_metadata();
>  }
>  
>  __meminit void zone_pcp_init(struct zone *zone)
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index 4548fcc66d74..4ca9f298f34e 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -201,6 +201,8 @@ static int __init alloc_node_page_ext(int nid)
>  		return -ENOMEM;
>  	NODE_DATA(nid)->node_page_ext = base;
>  	total_usage += table_size;
> +	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> +			    DIV_ROUND_UP(table_size, PAGE_SIZE));
>  	return 0;
>  }
>  
> @@ -255,12 +257,15 @@ static void *__meminit alloc_page_ext(size_t size, int nid)
>  	void *addr = NULL;
>  
>  	addr = alloc_pages_exact_nid(nid, size, flags);
> -	if (addr) {
> +	if (addr)
>  		kmemleak_alloc(addr, size, 1, flags);
> -		return addr;
> -	}
> +	else
> +		addr = vzalloc_node(size, nid);
>  
> -	addr = vzalloc_node(size, nid);
> +	if (addr) {
> +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> +				    DIV_ROUND_UP(size, PAGE_SIZE));
> +	}
>  
>  	return addr;
>  }
> @@ -303,18 +308,27 @@ static int __meminit init_section_page_ext(unsigned long pfn, int nid)
>  
>  static void free_page_ext(void *addr)
>  {
> +	size_t table_size;
> +	struct page *page;
> +	struct pglist_data *pgdat;
> +
> +	table_size = page_ext_size * PAGES_PER_SECTION;
> +
>  	if (is_vmalloc_addr(addr)) {
> +		page = vmalloc_to_page(addr);
> +		pgdat = page_pgdat(page);
>  		vfree(addr);
>  	} else {
> -		struct page *page = virt_to_page(addr);
> -		size_t table_size;
> -
> -		table_size = page_ext_size * PAGES_PER_SECTION;
> -
> +		page = virt_to_page(addr);
> +		pgdat = page_pgdat(page);
>  		BUG_ON(PageReserved(page));
>  		kmemleak_free(addr);
>  		free_pages_exact(addr, table_size);
>  	}
> +
> +	mod_node_page_state(pgdat, NR_PAGE_METADATA,
> +			    -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
> +
>  }
>  
>  static void __free_page_ext(unsigned long pfn)
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index a2cbe44c48e1..054b49539843 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -469,5 +469,13 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn,
>  	if (r < 0)
>  		return NULL;
>  
> +	if (system_state == SYSTEM_BOOTING) {
> +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> +				    DIV_ROUND_UP(end - start, PAGE_SIZE));
> +	} else {
> +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> +				    DIV_ROUND_UP(end - start, PAGE_SIZE));
> +	}
> +
>  	return pfn_to_page(pfn);
>  }
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 77d91e565045..0c100ae1cf8b 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -14,7 +14,7 @@
>  #include <linux/swap.h>
>  #include <linux/swapops.h>
>  #include <linux/bootmem_info.h>
> -
> +#include <linux/vmstat.h>
>  #include "internal.h"
>  #include <asm/dma.h>
>  
> @@ -465,6 +465,9 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
>  	 */
>  	sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true);
>  	sparsemap_buf_end = sparsemap_buf + size;
> +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> +	mod_node_early_perpage_metadata(nid, DIV_ROUND_UP(size, PAGE_SIZE));
> +#endif
>  }
>  
>  static void __init sparse_buffer_fini(void)
> @@ -641,6 +644,8 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
>  	unsigned long start = (unsigned long) pfn_to_page(pfn);
>  	unsigned long end = start + nr_pages * sizeof(struct page);
>  
> +	mod_node_page_state(page_pgdat(pfn_to_page(pfn)), NR_PAGE_METADATA,
> +			    -1L * (DIV_ROUND_UP(end - start, PAGE_SIZE)));
>  	vmemmap_free(start, end, altmap);
>  }
>  static void free_map_bootmem(struct page *memmap)
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 359460deb377..23e88d8c21b7 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1249,7 +1249,8 @@ const char * const vmstat_text[] = {
>  	"pgpromote_success",
>  	"pgpromote_candidate",
>  #endif
> -
> +	"nr_page_metadata",
> +	"nr_page_metadata_boot",
>  	/* enum writeback_stat_item counters */
>  	"nr_dirty_threshold",
>  	"nr_dirty_background_threshold",
> @@ -2278,4 +2279,27 @@ static int __init extfrag_debug_init(void)
>  }
>  
>  module_init(extfrag_debug_init);
> +
>  #endif
> +
> +/*
> + * Page metadata size (struct page and page_ext) in pages
> + */
> +static unsigned long early_perpage_metadata[MAX_NUMNODES] __initdata;
> +
> +void __init mod_node_early_perpage_metadata(int nid, long delta)
> +{
> +	early_perpage_metadata[nid] += delta;
> +}
> +
> +void __init store_early_perpage_metadata(void)
> +{
> +	int nid;
> +	struct pglist_data *pgdat;
> +
> +	for_each_online_pgdat(pgdat) {
> +		nid = pgdat->node_id;
> +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> +				    early_perpage_metadata[nid]);
> +	}
> +}
> -- 
> 2.43.0.472.g3155946c3a-goog
> 
> 
> 

Re: [PATCH v6 1/1] mm: report per-page metadata information

[David Rientjes]

On Fri, 5 Jan 2024, David Rientjes wrote:

> On Tue, 5 Dec 2023, Sourav Panda wrote:
> 
> > diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> > index 49ef12df631b..d5901d04e082 100644
> > --- a/Documentation/filesystems/proc.rst
> > +++ b/Documentation/filesystems/proc.rst
> > @@ -993,6 +993,7 @@ Example output. You may not have all of these fields.
> >      AnonPages:       4654780 kB
> >      Mapped:           266244 kB
> >      Shmem:              9976 kB
> > +    PageMetadata:     513419 kB
> >      KReclaimable:     517708 kB
> >      Slab:             660044 kB
> >      SReclaimable:     517708 kB
> > @@ -1095,6 +1096,8 @@ Mapped
> >                files which have been mmapped, such as libraries
> >  Shmem
> >                Total memory used by shared memory (shmem) and tmpfs
> > +PageMetadata
> > +              Memory used for per-page metadata
> >  KReclaimable
> >                Kernel allocations that the kernel will attempt to reclaim
> >                under memory pressure. Includes SReclaimable (below), and other
> > diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> > index 45af9a989d40..f141bb2a550d 100644
> > --- a/fs/proc/meminfo.c
> > +++ b/fs/proc/meminfo.c
> > @@ -39,7 +39,9 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
> >  	long available;
> >  	unsigned long pages[NR_LRU_LISTS];
> >  	unsigned long sreclaimable, sunreclaim;
> > +	unsigned long nr_page_metadata;
> 
> Initialize it here (if we actually need this variable)?
> 
> >  	int lru;
> > +	int nid;
> >  
> >  	si_meminfo(&i);
> >  	si_swapinfo(&i);
> > @@ -57,6 +59,10 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
> >  	sreclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B);
> >  	sunreclaim = global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B);
> >  
> > +	nr_page_metadata = 0;
> > +	for_each_online_node(nid)
> > +		nr_page_metadata += node_page_state(NODE_DATA(nid), NR_PAGE_METADATA);
> 
> Is this intended to be different than 
> global_node_page_state_pages(NR_PAGE_METADATA)?  
> 
> If so, any hint as to why we want to discount page metadata on offline 
> nodes?  We can't make an inference that metadata is always allocated 
> locally, memoryless nodes need things like struct page allocated on nodes 
> with memory.
> 

Sorry, meant a node with only ZONE_MOVABLE here so metadata can't be 
allocated locally.

But would be very interested to learn why this subtlety exists to sum up 
only online nodes.

> So even if a memoryless node is offline, we'd still be including its 
> metadata here with the current implementation.
> 
> Or maybe I'm missing a subtlety here for why this is not already 
> global_node_page_state_pages().
> 
> > +
> >  	show_val_kb(m, "MemTotal:       ", i.totalram);
> >  	show_val_kb(m, "MemFree:        ", i.freeram);
> >  	show_val_kb(m, "MemAvailable:   ", available);
> > @@ -104,6 +110,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
> >  	show_val_kb(m, "Mapped:         ",
> >  		    global_node_page_state(NR_FILE_MAPPED));
> >  	show_val_kb(m, "Shmem:          ", i.sharedram);
> > +	show_val_kb(m, "PageMetadata:   ", nr_page_metadata);
> >  	show_val_kb(m, "KReclaimable:   ", sreclaimable +
> >  		    global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE));
> >  	show_val_kb(m, "Slab:           ", sreclaimable + sunreclaim);
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 3c25226beeed..ef176152be7c 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -207,6 +207,10 @@ enum node_stat_item {
> >  	PGPROMOTE_SUCCESS,	/* promote successfully */
> >  	PGPROMOTE_CANDIDATE,	/* candidate pages to promote */
> >  #endif
> > +	NR_PAGE_METADATA,	/* Page metadata size (struct page and page_ext)
> > +				 * in pages
> > +				 */
> > +	NR_PAGE_METADATA_BOOT,	/* NR_PAGE_METADATA for bootmem */
> 
> So if some vmemmap pages are freed, then MemTotal could be incremented by 
> a portion of NR_PAGE_METADATA_BOOT and then this stat is decremented?  Is 
> the goal that the sum of MemTotal + SUM(nr_page_metadata_boot) is always 
> constant?
> 
> >  	NR_VM_NODE_STAT_ITEMS
> >  };
> >  
> > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> > index fed855bae6d8..af096a881f03 100644
> > --- a/include/linux/vmstat.h
> > +++ b/include/linux/vmstat.h
> > @@ -656,4 +656,8 @@ static inline void lruvec_stat_sub_folio(struct folio *folio,
> >  {
> >  	lruvec_stat_mod_folio(folio, idx, -folio_nr_pages(folio));
> >  }
> > +
> > +void __init mod_node_early_perpage_metadata(int nid, long delta);
> > +void __init store_early_perpage_metadata(void);
> > +
> >  #endif /* _LINUX_VMSTAT_H */
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index 87818ee7f01d..5b10d8d2b471 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -230,10 +230,14 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
> >   */
> >  static inline void free_vmemmap_page(struct page *page)
> >  {
> > -	if (PageReserved(page))
> > +	if (PageReserved(page)) {
> >  		free_bootmem_page(page);
> > -	else
> > +		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA_BOOT,
> > +				    -1);
> > +	} else {
> >  		__free_page(page);
> > +		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA, -1);
> > +	}
> >  }
> >  
> >  /* Free a list of the vmemmap pages */
> > @@ -389,6 +393,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
> >  		copy_page(page_to_virt(walk.reuse_page),
> >  			  (void *)walk.reuse_addr);
> >  		list_add(&walk.reuse_page->lru, vmemmap_pages);
> > +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, 1);
> >  	}
> >  
> >  	/*
> > @@ -437,14 +442,20 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
> >  	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
> >  	int nid = page_to_nid((struct page *)start);
> >  	struct page *page, *next;
> > +	int i;
> >  
> > -	while (nr_pages--) {
> > +	for (i = 0; i < nr_pages; i++) {
> >  		page = alloc_pages_node(nid, gfp_mask, 0);
> > -		if (!page)
> > +		if (!page) {
> > +			mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> > +					    i);
> >  			goto out;
> > +		}
> >  		list_add(&page->lru, list);
> >  	}
> >  
> > +	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, nr_pages);
> > +
> >  	return 0;
> >  out:
> >  	list_for_each_entry_safe(page, next, list, lru)
> > diff --git a/mm/mm_init.c b/mm/mm_init.c
> > index 077bfe393b5e..38f8e1f454a0 100644
> > --- a/mm/mm_init.c
> > +++ b/mm/mm_init.c
> > @@ -26,6 +26,7 @@
> >  #include <linux/pgtable.h>
> >  #include <linux/swap.h>
> >  #include <linux/cma.h>
> > +#include <linux/vmstat.h>
> >  #include "internal.h"
> >  #include "slab.h"
> >  #include "shuffle.h"
> > @@ -1656,6 +1657,8 @@ static void __init alloc_node_mem_map(struct pglist_data *pgdat)
> >  			panic("Failed to allocate %ld bytes for node %d memory map\n",
> >  			      size, pgdat->node_id);
> >  		pgdat->node_mem_map = map + offset;
> > +		mod_node_early_perpage_metadata(pgdat->node_id,
> > +						DIV_ROUND_UP(size, PAGE_SIZE));
> >  	}
> >  	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
> >  				__func__, pgdat->node_id, (unsigned long)pgdat,
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 733732e7e0ba..dd78017105b0 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -5636,6 +5636,7 @@ void __init setup_per_cpu_pageset(void)
> >  	for_each_online_pgdat(pgdat)
> >  		pgdat->per_cpu_nodestats =
> >  			alloc_percpu(struct per_cpu_nodestat);
> > +	store_early_perpage_metadata();
> >  }
> >  
> >  __meminit void zone_pcp_init(struct zone *zone)
> > diff --git a/mm/page_ext.c b/mm/page_ext.c
> > index 4548fcc66d74..4ca9f298f34e 100644
> > --- a/mm/page_ext.c
> > +++ b/mm/page_ext.c
> > @@ -201,6 +201,8 @@ static int __init alloc_node_page_ext(int nid)
> >  		return -ENOMEM;
> >  	NODE_DATA(nid)->node_page_ext = base;
> >  	total_usage += table_size;
> > +	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> > +			    DIV_ROUND_UP(table_size, PAGE_SIZE));
> >  	return 0;
> >  }
> >  
> > @@ -255,12 +257,15 @@ static void *__meminit alloc_page_ext(size_t size, int nid)
> >  	void *addr = NULL;
> >  
> >  	addr = alloc_pages_exact_nid(nid, size, flags);
> > -	if (addr) {
> > +	if (addr)
> >  		kmemleak_alloc(addr, size, 1, flags);
> > -		return addr;
> > -	}
> > +	else
> > +		addr = vzalloc_node(size, nid);
> >  
> > -	addr = vzalloc_node(size, nid);
> > +	if (addr) {
> > +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> > +				    DIV_ROUND_UP(size, PAGE_SIZE));
> > +	}
> >  
> >  	return addr;
> >  }
> > @@ -303,18 +308,27 @@ static int __meminit init_section_page_ext(unsigned long pfn, int nid)
> >  
> >  static void free_page_ext(void *addr)
> >  {
> > +	size_t table_size;
> > +	struct page *page;
> > +	struct pglist_data *pgdat;
> > +
> > +	table_size = page_ext_size * PAGES_PER_SECTION;
> > +
> >  	if (is_vmalloc_addr(addr)) {
> > +		page = vmalloc_to_page(addr);
> > +		pgdat = page_pgdat(page);
> >  		vfree(addr);
> >  	} else {
> > -		struct page *page = virt_to_page(addr);
> > -		size_t table_size;
> > -
> > -		table_size = page_ext_size * PAGES_PER_SECTION;
> > -
> > +		page = virt_to_page(addr);
> > +		pgdat = page_pgdat(page);
> >  		BUG_ON(PageReserved(page));
> >  		kmemleak_free(addr);
> >  		free_pages_exact(addr, table_size);
> >  	}
> > +
> > +	mod_node_page_state(pgdat, NR_PAGE_METADATA,
> > +			    -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
> > +
> >  }
> >  
> >  static void __free_page_ext(unsigned long pfn)
> > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> > index a2cbe44c48e1..054b49539843 100644
> > --- a/mm/sparse-vmemmap.c
> > +++ b/mm/sparse-vmemmap.c
> > @@ -469,5 +469,13 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn,
> >  	if (r < 0)
> >  		return NULL;
> >  
> > +	if (system_state == SYSTEM_BOOTING) {
> > +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> > +				    DIV_ROUND_UP(end - start, PAGE_SIZE));
> > +	} else {
> > +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> > +				    DIV_ROUND_UP(end - start, PAGE_SIZE));
> > +	}
> > +
> >  	return pfn_to_page(pfn);
> >  }
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index 77d91e565045..0c100ae1cf8b 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -14,7 +14,7 @@
> >  #include <linux/swap.h>
> >  #include <linux/swapops.h>
> >  #include <linux/bootmem_info.h>
> > -
> > +#include <linux/vmstat.h>
> >  #include "internal.h"
> >  #include <asm/dma.h>
> >  
> > @@ -465,6 +465,9 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
> >  	 */
> >  	sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true);
> >  	sparsemap_buf_end = sparsemap_buf + size;
> > +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> > +	mod_node_early_perpage_metadata(nid, DIV_ROUND_UP(size, PAGE_SIZE));
> > +#endif
> >  }
> >  
> >  static void __init sparse_buffer_fini(void)
> > @@ -641,6 +644,8 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
> >  	unsigned long start = (unsigned long) pfn_to_page(pfn);
> >  	unsigned long end = start + nr_pages * sizeof(struct page);
> >  
> > +	mod_node_page_state(page_pgdat(pfn_to_page(pfn)), NR_PAGE_METADATA,
> > +			    -1L * (DIV_ROUND_UP(end - start, PAGE_SIZE)));
> >  	vmemmap_free(start, end, altmap);
> >  }
> >  static void free_map_bootmem(struct page *memmap)
> > diff --git a/mm/vmstat.c b/mm/vmstat.c
> > index 359460deb377..23e88d8c21b7 100644
> > --- a/mm/vmstat.c
> > +++ b/mm/vmstat.c
> > @@ -1249,7 +1249,8 @@ const char * const vmstat_text[] = {
> >  	"pgpromote_success",
> >  	"pgpromote_candidate",
> >  #endif
> > -
> > +	"nr_page_metadata",
> > +	"nr_page_metadata_boot",
> >  	/* enum writeback_stat_item counters */
> >  	"nr_dirty_threshold",
> >  	"nr_dirty_background_threshold",
> > @@ -2278,4 +2279,27 @@ static int __init extfrag_debug_init(void)
> >  }
> >  
> >  module_init(extfrag_debug_init);
> > +
> >  #endif
> > +
> > +/*
> > + * Page metadata size (struct page and page_ext) in pages
> > + */
> > +static unsigned long early_perpage_metadata[MAX_NUMNODES] __initdata;
> > +
> > +void __init mod_node_early_perpage_metadata(int nid, long delta)
> > +{
> > +	early_perpage_metadata[nid] += delta;
> > +}
> > +
> > +void __init store_early_perpage_metadata(void)
> > +{
> > +	int nid;
> > +	struct pglist_data *pgdat;
> > +
> > +	for_each_online_pgdat(pgdat) {
> > +		nid = pgdat->node_id;
> > +		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> > +				    early_perpage_metadata[nid]);
> > +	}
> > +}
> > -- 
> > 2.43.0.472.g3155946c3a-goog
> > 
> > 
> > 
> 

Re: [PATCH v6 1/1] mm: report per-page metadata information

[Sourav Panda]

[-- Attachment #1: Type: text/plain, Size: 15611 bytes --]

On Fri, Jan 5, 2024 at 4:38 PM David Rientjes <rientjes@google.com> wrote:

> On Fri, 5 Jan 2024, David Rientjes wrote:
>
> > On Tue, 5 Dec 2023, Sourav Panda wrote:
> >
> > > diff --git a/Documentation/filesystems/proc.rst
> b/Documentation/filesystems/proc.rst
> > > index 49ef12df631b..d5901d04e082 100644
> > > --- a/Documentation/filesystems/proc.rst
> > > +++ b/Documentation/filesystems/proc.rst
> > > @@ -993,6 +993,7 @@ Example output. You may not have all of these
> fields.
> > >      AnonPages:       4654780 kB
> > >      Mapped:           266244 kB
> > >      Shmem:              9976 kB
> > > +    PageMetadata:     513419 kB
> > >      KReclaimable:     517708 kB
> > >      Slab:             660044 kB
> > >      SReclaimable:     517708 kB
> > > @@ -1095,6 +1096,8 @@ Mapped
> > >                files which have been mmapped, such as libraries
> > >  Shmem
> > >                Total memory used by shared memory (shmem) and tmpfs
> > > +PageMetadata
> > > +              Memory used for per-page metadata
> > >  KReclaimable
> > >                Kernel allocations that the kernel will attempt to
> reclaim
> > >                under memory pressure. Includes SReclaimable (below),
> and other
> > > diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> > > index 45af9a989d40..f141bb2a550d 100644
> > > --- a/fs/proc/meminfo.c
> > > +++ b/fs/proc/meminfo.c
> > > @@ -39,7 +39,9 @@ static int meminfo_proc_show(struct seq_file *m,
> void *v)
> > >     long available;
> > >     unsigned long pages[NR_LRU_LISTS];
> > >     unsigned long sreclaimable, sunreclaim;
> > > +   unsigned long nr_page_metadata;
> >
> > Initialize it here (if we actually need this variable)?
> >


Thanks David! I will make this change in v7.


>
> > >     int lru;
> > > +   int nid;
> > >
> > >     si_meminfo(&i);
> > >     si_swapinfo(&i);
> > > @@ -57,6 +59,10 @@ static int meminfo_proc_show(struct seq_file *m,
> void *v)
> > >     sreclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B);
> > >     sunreclaim = global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B);
> > >
> > > +   nr_page_metadata = 0;
> > > +   for_each_online_node(nid)
> > > +           nr_page_metadata += node_page_state(NODE_DATA(nid),
> NR_PAGE_METADATA);
> >
> > Is this intended to be different than
> > global_node_page_state_pages(NR_PAGE_METADATA)?
> >


We also present the metrics in /proc/meminfo to export the value in a
readable format where all the values are consistently in kB (unlike vmstat
with varying units).


> > If so, any hint as to why we want to discount page metadata on offline
> > nodes?  We can't make an inference that metadata is always allocated
> > locally, memoryless nodes need things like struct page allocated on
> nodes
> > with memory.
> >
>
> Sorry, meant a node with only ZONE_MOVABLE here so metadata can't be
> allocated locally.


When we have a ZONE_MOVABLE’s page's metadata on another node, it would NOT
be discounted. It would be accounted for on the other node.


>
> But would be very interested to learn why this subtlety exists to sum up
> only online nodes.
>
> > So even if a memoryless node is offline, we'd still be including its
> > metadata here with the current implementation.
> >
> > Or maybe I'm missing a subtlety here for why this is not already
> > global_node_page_state_pages().
> >


If I understood correctly, as long as the memory is not hotplugged, it
won't have any page metadata and thus we would NOT include its metadata.
The moment the memory is hotplugged or hot-unplugged, the metadata will be
incremented or decremented, correspondingly.


>
> > > +
> > >     show_val_kb(m, "MemTotal:       ", i.totalram);
> > >     show_val_kb(m, "MemFree:        ", i.freeram);
> > >     show_val_kb(m, "MemAvailable:   ", available);
> > > @@ -104,6 +110,7 @@ static int meminfo_proc_show(struct seq_file *m,
> void *v)
> > >     show_val_kb(m, "Mapped:         ",
> > >                 global_node_page_state(NR_FILE_MAPPED));
> > >     show_val_kb(m, "Shmem:          ", i.sharedram);
> > > +   show_val_kb(m, "PageMetadata:   ", nr_page_metadata);
> > >     show_val_kb(m, "KReclaimable:   ", sreclaimable +
> > >                 global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE));
> > >     show_val_kb(m, "Slab:           ", sreclaimable + sunreclaim);
> > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > > index 3c25226beeed..ef176152be7c 100644
> > > --- a/include/linux/mmzone.h
> > > +++ b/include/linux/mmzone.h
> > > @@ -207,6 +207,10 @@ enum node_stat_item {
> > >     PGPROMOTE_SUCCESS,      /* promote successfully */
> > >     PGPROMOTE_CANDIDATE,    /* candidate pages to promote */
> > >  #endif
> > > +   NR_PAGE_METADATA,       /* Page metadata size (struct page and
> page_ext)
> > > +                            * in pages
> > > +                            */
> > > +   NR_PAGE_METADATA_BOOT,  /* NR_PAGE_METADATA for bootmem */
> >
> > So if some vmemmap pages are freed, then MemTotal could be incremented
> by
> > a portion of NR_PAGE_METADATA_BOOT and then this stat is decremented?
> Is
> > the goal that the sum of MemTotal + SUM(nr_page_metadata_boot) is always
> > constant?
> >


Yep, this is correct.


>
> > >     NR_VM_NODE_STAT_ITEMS
> > >  };
> > >
> > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> > > index fed855bae6d8..af096a881f03 100644
> > > --- a/include/linux/vmstat.h
> > > +++ b/include/linux/vmstat.h
> > > @@ -656,4 +656,8 @@ static inline void lruvec_stat_sub_folio(struct
> folio *folio,
> > >  {
> > >     lruvec_stat_mod_folio(folio, idx, -folio_nr_pages(folio));
> > >  }
> > > +
> > > +void __init mod_node_early_perpage_metadata(int nid, long delta);
> > > +void __init store_early_perpage_metadata(void);
> > > +
> > >  #endif /* _LINUX_VMSTAT_H */
> > > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > > index 87818ee7f01d..5b10d8d2b471 100644
> > > --- a/mm/hugetlb_vmemmap.c
> > > +++ b/mm/hugetlb_vmemmap.c
> > > @@ -230,10 +230,14 @@ static int vmemmap_remap_range(unsigned long
> start, unsigned long end,
> > >   */
> > >  static inline void free_vmemmap_page(struct page *page)
> > >  {
> > > -   if (PageReserved(page))
> > > +   if (PageReserved(page)) {
> > >             free_bootmem_page(page);
> > > -   else
> > > +           mod_node_page_state(page_pgdat(page),
> NR_PAGE_METADATA_BOOT,
> > > +                               -1);
> > > +   } else {
> > >             __free_page(page);
> > > +           mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA,
> -1);
> > > +   }
> > >  }
> > >
> > >  /* Free a list of the vmemmap pages */
> > > @@ -389,6 +393,7 @@ static int vmemmap_remap_free(unsigned long start,
> unsigned long end,
> > >             copy_page(page_to_virt(walk.reuse_page),
> > >                       (void *)walk.reuse_addr);
> > >             list_add(&walk.reuse_page->lru, vmemmap_pages);
> > > +           mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, 1);
> > >     }
> > >
> > >     /*
> > > @@ -437,14 +442,20 @@ static int alloc_vmemmap_page_list(unsigned long
> start, unsigned long end,
> > >     unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
> > >     int nid = page_to_nid((struct page *)start);
> > >     struct page *page, *next;
> > > +   int i;
> > >
> > > -   while (nr_pages--) {
> > > +   for (i = 0; i < nr_pages; i++) {
> > >             page = alloc_pages_node(nid, gfp_mask, 0);
> > > -           if (!page)
> > > +           if (!page) {
> > > +                   mod_node_page_state(NODE_DATA(nid),
> NR_PAGE_METADATA,
> > > +                                       i);
> > >                     goto out;
> > > +           }
> > >             list_add(&page->lru, list);
> > >     }
> > >
> > > +   mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, nr_pages);
> > > +
> > >     return 0;
> > >  out:
> > >     list_for_each_entry_safe(page, next, list, lru)
> > > diff --git a/mm/mm_init.c b/mm/mm_init.c
> > > index 077bfe393b5e..38f8e1f454a0 100644
> > > --- a/mm/mm_init.c
> > > +++ b/mm/mm_init.c
> > > @@ -26,6 +26,7 @@
> > >  #include <linux/pgtable.h>
> > >  #include <linux/swap.h>
> > >  #include <linux/cma.h>
> > > +#include <linux/vmstat.h>
> > >  #include "internal.h"
> > >  #include "slab.h"
> > >  #include "shuffle.h"
> > > @@ -1656,6 +1657,8 @@ static void __init alloc_node_mem_map(struct
> pglist_data *pgdat)
> > >                     panic("Failed to allocate %ld bytes for node %d
> memory map\n",
> > >                           size, pgdat->node_id);
> > >             pgdat->node_mem_map = map + offset;
> > > +           mod_node_early_perpage_metadata(pgdat->node_id,
> > > +                                           DIV_ROUND_UP(size,
> PAGE_SIZE));
> > >     }
> > >     pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
> > >                             __func__, pgdat->node_id, (unsigned
> long)pgdat,
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > index 733732e7e0ba..dd78017105b0 100644
> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -5636,6 +5636,7 @@ void __init setup_per_cpu_pageset(void)
> > >     for_each_online_pgdat(pgdat)
> > >             pgdat->per_cpu_nodestats =
> > >                     alloc_percpu(struct per_cpu_nodestat);
> > > +   store_early_perpage_metadata();
> > >  }
> > >
> > >  __meminit void zone_pcp_init(struct zone *zone)
> > > diff --git a/mm/page_ext.c b/mm/page_ext.c
> > > index 4548fcc66d74..4ca9f298f34e 100644
> > > --- a/mm/page_ext.c
> > > +++ b/mm/page_ext.c
> > > @@ -201,6 +201,8 @@ static int __init alloc_node_page_ext(int nid)
> > >             return -ENOMEM;
> > >     NODE_DATA(nid)->node_page_ext = base;
> > >     total_usage += table_size;
> > > +   mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> > > +                       DIV_ROUND_UP(table_size, PAGE_SIZE));
> > >     return 0;
> > >  }
> > >
> > > @@ -255,12 +257,15 @@ static void *__meminit alloc_page_ext(size_t
> size, int nid)
> > >     void *addr = NULL;
> > >
> > >     addr = alloc_pages_exact_nid(nid, size, flags);
> > > -   if (addr) {
> > > +   if (addr)
> > >             kmemleak_alloc(addr, size, 1, flags);
> > > -           return addr;
> > > -   }
> > > +   else
> > > +           addr = vzalloc_node(size, nid);
> > >
> > > -   addr = vzalloc_node(size, nid);
> > > +   if (addr) {
> > > +           mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> > > +                               DIV_ROUND_UP(size, PAGE_SIZE));
> > > +   }
> > >
> > >     return addr;
> > >  }
> > > @@ -303,18 +308,27 @@ static int __meminit
> init_section_page_ext(unsigned long pfn, int nid)
> > >
> > >  static void free_page_ext(void *addr)
> > >  {
> > > +   size_t table_size;
> > > +   struct page *page;
> > > +   struct pglist_data *pgdat;
> > > +
> > > +   table_size = page_ext_size * PAGES_PER_SECTION;
> > > +
> > >     if (is_vmalloc_addr(addr)) {
> > > +           page = vmalloc_to_page(addr);
> > > +           pgdat = page_pgdat(page);
> > >             vfree(addr);
> > >     } else {
> > > -           struct page *page = virt_to_page(addr);
> > > -           size_t table_size;
> > > -
> > > -           table_size = page_ext_size * PAGES_PER_SECTION;
> > > -
> > > +           page = virt_to_page(addr);
> > > +           pgdat = page_pgdat(page);
> > >             BUG_ON(PageReserved(page));
> > >             kmemleak_free(addr);
> > >             free_pages_exact(addr, table_size);
> > >     }
> > > +
> > > +   mod_node_page_state(pgdat, NR_PAGE_METADATA,
> > > +                       -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
> > > +
> > >  }
> > >
> > >  static void __free_page_ext(unsigned long pfn)
> > > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> > > index a2cbe44c48e1..054b49539843 100644
> > > --- a/mm/sparse-vmemmap.c
> > > +++ b/mm/sparse-vmemmap.c
> > > @@ -469,5 +469,13 @@ struct page * __meminit
> __populate_section_memmap(unsigned long pfn,
> > >     if (r < 0)
> > >             return NULL;
> > >
> > > +   if (system_state == SYSTEM_BOOTING) {
> > > +           mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> > > +                               DIV_ROUND_UP(end - start, PAGE_SIZE));
> > > +   } else {
> > > +           mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
> > > +                               DIV_ROUND_UP(end - start, PAGE_SIZE));
> > > +   }
> > > +
> > >     return pfn_to_page(pfn);
> > >  }
> > > diff --git a/mm/sparse.c b/mm/sparse.c
> > > index 77d91e565045..0c100ae1cf8b 100644
> > > --- a/mm/sparse.c
> > > +++ b/mm/sparse.c
> > > @@ -14,7 +14,7 @@
> > >  #include <linux/swap.h>
> > >  #include <linux/swapops.h>
> > >  #include <linux/bootmem_info.h>
> > > -
> > > +#include <linux/vmstat.h>
> > >  #include "internal.h"
> > >  #include <asm/dma.h>
> > >
> > > @@ -465,6 +465,9 @@ static void __init sparse_buffer_init(unsigned
> long size, int nid)
> > >      */
> > >     sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid,
> true);
> > >     sparsemap_buf_end = sparsemap_buf + size;
> > > +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> > > +   mod_node_early_perpage_metadata(nid, DIV_ROUND_UP(size,
> PAGE_SIZE));
> > > +#endif
> > >  }
> > >
> > >  static void __init sparse_buffer_fini(void)
> > > @@ -641,6 +644,8 @@ static void depopulate_section_memmap(unsigned
> long pfn, unsigned long nr_pages,
> > >     unsigned long start = (unsigned long) pfn_to_page(pfn);
> > >     unsigned long end = start + nr_pages * sizeof(struct page);
> > >
> > > +   mod_node_page_state(page_pgdat(pfn_to_page(pfn)), NR_PAGE_METADATA,
> > > +                       -1L * (DIV_ROUND_UP(end - start, PAGE_SIZE)));
> > >     vmemmap_free(start, end, altmap);
> > >  }
> > >  static void free_map_bootmem(struct page *memmap)
> > > diff --git a/mm/vmstat.c b/mm/vmstat.c
> > > index 359460deb377..23e88d8c21b7 100644
> > > --- a/mm/vmstat.c
> > > +++ b/mm/vmstat.c
> > > @@ -1249,7 +1249,8 @@ const char * const vmstat_text[] = {
> > >     "pgpromote_success",
> > >     "pgpromote_candidate",
> > >  #endif
> > > -
> > > +   "nr_page_metadata",
> > > +   "nr_page_metadata_boot",
> > >     /* enum writeback_stat_item counters */
> > >     "nr_dirty_threshold",
> > >     "nr_dirty_background_threshold",
> > > @@ -2278,4 +2279,27 @@ static int __init extfrag_debug_init(void)
> > >  }
> > >
> > >  module_init(extfrag_debug_init);
> > > +
> > >  #endif
> > > +
> > > +/*
> > > + * Page metadata size (struct page and page_ext) in pages
> > > + */
> > > +static unsigned long early_perpage_metadata[MAX_NUMNODES] __initdata;
> > > +
> > > +void __init mod_node_early_perpage_metadata(int nid, long delta)
> > > +{
> > > +   early_perpage_metadata[nid] += delta;
> > > +}
> > > +
> > > +void __init store_early_perpage_metadata(void)
> > > +{
> > > +   int nid;
> > > +   struct pglist_data *pgdat;
> > > +
> > > +   for_each_online_pgdat(pgdat) {
> > > +           nid = pgdat->node_id;
> > > +           mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
> > > +                               early_perpage_metadata[nid]);
> > > +   }
> > > +}
> > > --
> > > 2.43.0.472.g3155946c3a-goog
> > >
> > >
> > >
> >
>

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