Commit 15995a35 authored by Sourav Panda's avatar Sourav Panda Committed by Andrew Morton
Browse files

mm: report per-page metadata information 

Today, we do not have any observability of per-page metadata and how much
it takes away from the machine capacity.  Thus, we want to describe the
amount of memory that is going towards per-page metadata, which can vary
depending on build configuration, machine architecture, and system use.

This patch adds 2 fields to /proc/vmstat that can used as shown below:

Accounting per-page metadata allocated by boot-allocator:
	/proc/vmstat:nr_memmap_boot * PAGE_SIZE

Accounting per-page metadata allocated by buddy-allocator:
	/proc/vmstat:nr_memmap * PAGE_SIZE

Accounting total Perpage metadata allocated on the machine:
	(/proc/vmstat:nr_memmap_boot +
	 /proc/vmstat:nr_memmap) * PAGE_SIZE

Utility for userspace:

Observability: Describe the amount of memory overhead that is going to
per-page metadata on the system at any given time since this overhead is
not currently observable.

Debugging: Tracking the changes or absolute value in struct pages can help
detect anomalies as they can be correlated with other metrics in the
machine (e.g., memtotal, number of huge pages, etc).

page_ext overheads: Some kernel features such as page_owner
page_table_check that use page_ext can be optionally enabled via kernel
parameters.  Having the total per-page metadata information helps users
precisely measure impact.  Furthermore, page-metadata metrics will reflect
the amount of struct pages reliquished (or overhead reduced) when
hugetlbfs pages are reserved which will vary depending on whether hugetlb
vmemmap optimization is enabled or not.

For background and results see:
lore.kernel.org/all/20240220214558.3377482-1-souravpanda@google.com

Link: https://lkml.kernel.org/r/20240605222751.1406125-1-souravpanda@google.com


Signed-off-by: default avatarSourav Panda <souravpanda@google.com>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Reviewed-by: default avatarPasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Chen Linxuan <chenlinxuan@uniontech.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ivan Babrou <ivan@cloudflare.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tomas Mudrunka <tomas.mudrunka@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Xu <weixugc@google.com>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 8192bc03

include/linux/mmzone.h

+2 −0
Original line number Diff line number Diff line
@@ -220,6 +220,8 @@ enum node_stat_item { 
	PGDEMOTE_KSWAPD,

	PGDEMOTE_DIRECT,

	PGDEMOTE_KHUGEPAGED,

	NR_MEMMAP, /* page metadata allocated through buddy allocator */

	NR_MEMMAP_BOOT, /* page metadata allocated through boot allocator */

	NR_VM_NODE_STAT_ITEMS

};

include/linux/vmstat.h

+4 −0
Original line number Diff line number Diff line
@@ -624,4 +624,8 @@ static inline void lruvec_stat_sub_folio(struct folio *folio, 
{

	lruvec_stat_mod_folio(folio, idx, -folio_nr_pages(folio));

}



void __meminit mod_node_early_perpage_metadata(int nid, long delta);

void __meminit store_early_perpage_metadata(void);



#endif /* _LINUX_VMSTAT_H */

mm/hugetlb_vmemmap.c

+13 −4
Original line number Diff line number Diff line
@@ -184,10 +184,13 @@ 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_MEMMAP_BOOT, -1);

	} else {

		__free_page(page);

		mod_node_page_state(page_pgdat(page), NR_MEMMAP, -1);

	}

}



/* Free a list of the vmemmap pages */
@@ -338,6 +341,7 @@ 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_MEMMAP, 1);

	}



	/*
@@ -384,14 +388,19 @@ 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_MEMMAP, i);

			goto out;

		}

		list_add(&page->lru, list);

	}



	mod_node_page_state(NODE_DATA(nid), NR_MEMMAP, nr_pages);



	return 0;

out:

	list_for_each_entry_safe(page, next, list, lru)

mm/mm_init.c

+3 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 
#include <linux/cma.h>

#include <linux/crash_dump.h>

#include <linux/execmem.h>

#include <linux/vmstat.h>

#include "internal.h"

#include "slab.h"

#include "shuffle.h"
@@ -1618,6 +1619,8 @@ 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,

		 (unsigned long)pgdat->node_mem_map);

mm/page_alloc.c

+1 −0
Original line number Diff line number Diff line
@@ -5738,6 +5738,7 @@ 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)