Re: [PATCH v1 1/1] mm: report per-page metadata information

From: Mike Rapoport
Date: Wed Sep 13 2023 - 16:52:11 EST

On Wed, Sep 13, 2023 at 10:30:00AM -0700, 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.
>
> 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 | 8 +++++++-
> mm/hugetlb_vmemmap.c | 9 ++++++++-
> mm/mm_init.c | 3 +++
> mm/page_alloc.c | 1 +
> mm/page_ext.c | 17 +++++++++++++----
> mm/sparse-vmemmap.c | 3 +++
> mm/sparse.c | 7 ++++++-
> mm/vmstat.c | 21 +++++++++++++++++++++
> 13 files changed, 81 insertions(+), 7 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..b5c292560f37 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 writeout_early_perpage_metadata(void);
> +
> #endif /* _LINUX_VMSTAT_H */
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ba6d39b71cb1..ca36751be50e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1758,6 +1758,10 @@ 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
> + __mod_node_page_state(NODE_DATA(page_to_nid(&folio->page)),
> + NR_PAGE_METADATA, -huge_page_order(h));

I don't think memory map will change here with classic SPARSEMEM

> +#endif
> __free_pages(&folio->page, huge_page_order(h));
> }
> }
> @@ -2143,7 +2147,9 @@ static struct folio *alloc_buddy_hugetlb_folio(struct hstate *h,
> __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
> return NULL;
> }
> -
> +#ifndef CONFIG_SPARSEMEM_VMEMMAP
> + __mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, huge_page_order(h));
> +#endif
> __count_vm_event(HTLB_BUDDY_PGALLOC);
> return page_folio(page);
> }
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 4b9734777f69..7f920bfa8e79 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -214,6 +214,8 @@ static inline void free_vmemmap_page(struct page *page)
> free_bootmem_page(page);
> else
> __free_page(page);
> + __mod_node_page_state(NODE_DATA(page_to_nid(page)),
> + NR_PAGE_METADATA, -1);
> }
>
> /* Free a list of the vmemmap pages */
> @@ -336,6 +338,7 @@ 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);
>
> /*
> * In order to make remapping routine most efficient for the huge pages,
> @@ -387,8 +390,12 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
>
> while (nr_pages--) {
> page = alloc_pages_node(nid, gfp_mask, 0);
> - if (!page)
> + if (!page) {
> goto out;
> + } else {
> + __mod_node_page_state(NODE_DATA(page_to_nid(page)),
> + NR_PAGE_METADATA, 1);

We can update this once for nr_pages outside the loop, cannot we?

> + }
> list_add_tail(&page->lru, list);
> }
>
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 50f2f34745af..e02dce7e2e9a 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,
> + PAGE_ALIGN(size) >> PAGE_SHIFT);
> }
> 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 0c5be12f9336..4e295d5087f4 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);
> + writeout_early_perpage_metadata();

Why it's called here?
You can copy early stats to actual node stats as soon as the nodes and page
allocator are initialized.

> }
>
> __meminit void zone_pcp_init(struct zone *zone)
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index 4548fcc66d74..b5b9d3079e20 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,
> + PAGE_ALIGN(table_size) >> PAGE_SHIFT);
> 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,
> + PAGE_ALIGN(size) >> PAGE_SHIFT);
> + }
>
> return addr;
> }
> @@ -314,6 +319,10 @@ static void free_page_ext(void *addr)
> BUG_ON(PageReserved(page));
> kmemleak_free(addr);
> free_pages_exact(addr, table_size);
> +
> + __mod_node_page_state(NODE_DATA(page_to_nid(page)), NR_PAGE_METADATA,
> + (long)-1 * (PAGE_ALIGN(table_size) >> PAGE_SHIFT));
> +

what happens with vmalloc()ed page_ext?

> }
> }
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index a2cbe44c48e1..e33f302db7c6 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,
> + PAGE_ALIGN(end - start) >> PAGE_SHIFT);
> +
> return pfn_to_page(pfn);
> }
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 77d91e565045..db78233a85ef 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, PAGE_ALIGN(size) >> PAGE_SHIFT);

All early struct pages are allocated in memmap_alloc(). It'd make sense to update
the counter there.

> +#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(NODE_DATA(page_to_nid(pfn_to_page(pfn))), NR_PAGE_METADATA,
> + (long)-1 * (PAGE_ALIGN(end - start) >> PAGE_SHIFT));
> 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..731eb5264b49 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 +2275,24 @@ static int __init extfrag_debug_init(void)
> }
>
> module_init(extfrag_debug_init);
> +
> +// Page metadata size (struct page and page_ext) in pages
> +unsigned long early_perpage_metadata[MAX_NUMNODES] __initdata;

static?

> +
> +void __init mod_node_early_perpage_metadata(int nid, long delta)
> +{
> + early_perpage_metadata[nid] += delta;
> +}
> +
> +void __init writeout_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]);
> + }
> +}
> #endif
> --
> 2.42.0.283.g2d96d420d3-goog
>

--
Sincerely yours,
Mike.