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Date: Fri, 5 Jan 2024 16:38:23 -0800 (PST)
From: David Rientjes <rientjes@...gle.com>
To: Sourav Panda <souravpanda@...gle.com>
cc: corbet@....net, gregkh@...uxfoundation.org, rafael@...nel.org,
Andrew Morton <akpm@...ux-foundation.org>, mike.kravetz@...cle.com,
muchun.song@...ux.dev, rppt@...nel.org, david@...hat.com,
rdunlap@...radead.org, chenlinxuan@...ontech.com, yang.yang29@....com.cn,
tomas.mudrunka@...il.com, bhelgaas@...gle.com, ivan@...udflare.com,
pasha.tatashin@...een.com, yosryahmed@...gle.com, hannes@...xchg.org,
shakeelb@...gle.com, kirill.shutemov@...ux.intel.com,
wangkefeng.wang@...wei.com, adobriyan@...il.com,
Vlastimil Babka <vbabka@...e.cz>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>, surenb@...gle.com,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-mm@...ck.org,
Matthew Wilcox <willy@...radead.org>, weixugc@...gle.com
Subject: Re: [PATCH v6 1/1] mm: report per-page metadata information
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
> >
> >
> >
>
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