On Tue, Oct 31, 2023 at 8:38 PM Muchun Song <muchun.song@xxxxxxxxx> wrote:
On 2023/11/1 06:38, Sourav Panda wrote:
> Adds a new per-node PageMetadata field to
> /sys/devices/system/node/nodeN/meminfo
> 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. While on the other hand,
> per-page metadata would include both memblock and buddy allocations.
>
> 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@xxxxxxxxxx>
> Signed-off-by: Sourav Panda <souravpanda@xxxxxxxxxx>
> ---
> Documentation/filesystems/proc.rst | 3 +++
> drivers/base/node.c | 2 ++
> fs/proc/meminfo.c | 7 +++++++
> include/linux/mmzone.h | 3 +++
> include/linux/vmstat.h | 4 ++++
> mm/hugetlb.c | 11 ++++++++--
> mm/hugetlb_vmemmap.c | 8 ++++++--
> mm/mm_init.c | 3 +++
> mm/page_alloc.c | 1 +
> mm/page_ext.c | 32 +++++++++++++++++++++---------
> mm/sparse-vmemmap.c | 3 +++
> mm/sparse.c | 7 ++++++-
> mm/vmstat.c | 24 ++++++++++++++++++++++
> 13 files changed, 94 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 2b59cff8be17..c121f2ef9432 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -987,6 +987,7 @@ 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
> @@ -1089,6 +1090,8 @@ 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/drivers/base/node.c b/drivers/base/node.c
> index 493d533f8375..da728542265f 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -428,6 +428,7 @@ static ssize_t node_read_meminfo(struct device *dev,
> "Node %d Mapped: %8lu kB\n"
> "Node %d AnonPages: %8lu kB\n"
> "Node %d Shmem: %8lu kB\n"
> + "Node %d PageMetadata: %8lu kB\n"
> "Node %d KernelStack: %8lu kB\n"
> #ifdef CONFIG_SHADOW_CALL_STACK
> "Node %d ShadowCallStack:%8lu kB\n"
> @@ -458,6 +459,7 @@ static ssize_t node_read_meminfo(struct device *dev,
> nid, K(node_page_state(pgdat, NR_FILE_MAPPED)),
> nid, K(node_page_state(pgdat, NR_ANON_MAPPED)),
> nid, K(i.sharedram),
> + nid, K(node_page_state(pgdat, NR_PAGE_METADATA)),
> nid, node_page_state(pgdat, NR_KERNEL_STACK_KB),
> #ifdef CONFIG_SHADOW_CALL_STACK
> nid, node_page_state(pgdat, NR_KERNEL_SCS_KB),
> 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 4106fbc5b4b3..dda1ad522324 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -207,6 +207,9 @@ 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_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.c b/mm/hugetlb.c
> index 1301ba7b2c9a..cd3158a9c7f3 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1790,6 +1790,9 @@ static void __update_and_free_hugetlb_folio(struct hstate *h,
> destroy_compound_gigantic_folio(folio, huge_page_order(h));
> free_gigantic_folio(folio, huge_page_order(h));
> } else {
> +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> + __node_stat_sub_folio(folio, NR_PAGE_METADATA);
> +#endif
> __free_pages(&folio->page, huge_page_order(h));
> }
> }
> @@ -2125,6 +2128,7 @@ static struct folio *alloc_buddy_hugetlb_folio(struct hstate *h,
> struct page *page;
> bool alloc_try_hard = true;
> bool retry = true;
> + struct folio *folio;
>
> /*
> * By default we always try hard to allocate the page with
> @@ -2175,9 +2179,12 @@ static struct folio *alloc_buddy_hugetlb_folio(struct hstate *h,
> __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
> return NULL;
> }
> -
> + folio = page_folio(page);
> +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> + __node_stat_add_folio(folio, NR_PAGE_METADATA)
Seems you have not tested this patch with CONFIG_SPARSEMEM_VMEMMAP disabled.
You missed ";" in the end.
Thanks for reviewing this patch. I will submit v5 by testing against FLATMEM and
SPARSEMEM (VMEMMAP disabled) memory model on ARM32. This error was introduced
in v4.
> +#endif
I am curious why we should account HugeTLB pages as metadata.
When HugeTLB pages are reserved, memory pertaining to redundant `struct page` are
returned to the buddy allocator for other uses. This essentially reflects the change in the
amount of `struct pages` when HugeTLB pages are reserved and free'd.
> __count_vm_event(HTLB_BUDDY_PGALLOC);
> - return page_folio(page);
> + return folio;
> }
>
> /*
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 4b9734777f69..804a93d18cab 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -214,6 +214,7 @@ static inline void free_vmemmap_page(struct page *page)
> free_bootmem_page(page);
> else
> __free_page(page);
> + __mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA, -1);
> }
>
> /* Free a list of the vmemmap pages */
> @@ -336,6 +337,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
> (void *)walk.reuse_addr);
> list_add(&walk.reuse_page->lru, &vmemmap_pages);
> }
> + __mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, 1);
What if allocation of walk.reuse_page fails?
Thank you for pointing this out. I will move the NR_PAGE_METADATA update within the
if ( walk.reuse_page ) clause to cover the case where walk.reuse_page fails.
>
> /*
> * In order to make remapping routine most efficient for the huge pages,
> @@ -381,14 +383,16 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
> struct list_head *list)
> {
> gfp_t gfp_mask = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_THISNODE;
> - unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
> + unsigned long nr_pages = DIV_ROUND_UP(end - start, PAGE_SIZE);
"end - start" is always multiple of PAGE_SIZE, why we need DIV_ROUND_UP
here?
Thank you. I agree with this and will revert this change in v5.
> 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)
> goto out;
> + __mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA, 1);
> list_add_tail(&page->lru, list);
> }
Count one by ine is really inefficient. Can't we count *nr_pages* at
one time?
Thanks for suggesting this optimization. I will modify the implementation to update the
metadata once as opposed to every iteration.
>
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 50f2f34745af..6997bf00945b 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 85741403948f..522dc0c52610 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5443,6 +5443,7 @@ 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..d8d6db9c3d75 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,
> + 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..2bc67b2c2aa2 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -469,5 +469,8 @@ struct page * __meminit __populate_section_memmap(unsigned long pfn,
> if (r < 0)
> return NULL;
>
> + __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..7f67b5486cd1 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 00e81e99c6ee..070d2b3d2bcc 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1245,6 +1245,7 @@ const char * const vmstat_text[] = {
> "pgpromote_success",
> "pgpromote_candidate",
> #endif
> + "nr_page_metadata",
>
> /* enum writeback_stat_item counters */
> "nr_dirty_threshold",
> @@ -2274,4 +2275,27 @@ 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,
> + early_perpage_metadata[nid]);
> + }
> +}
