totalram_pages, zone->managed_pages and totalhigh_pages updates are protected by managed_page_count_lock, but readers never care about it. Convert these variables to atomic to avoid readers potentially seeing a store tear. This patch converts zone->managed_pages. Subsequent patches will convert totalram_panges, totalhigh_pages and eventually managed_page_count_lock will be removed. Main motivation was that managed_page_count_lock handling was complicating things. It was discussed in length here, https://lore.kernel.org/patchwork/patch/995739/#1181785 So it seemes better to remove the lock and convert variables to atomic, with preventing poteintial store-to-read tearing as a bonus. Suggested-by: Michal Hocko <mhocko@xxxxxxxx> Suggested-by: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Arun KS <arunks@xxxxxxxxxxxxxx> Reviewed-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> --- Most of the changes are done by below coccinelle script, @@ struct zone *z; expression e1; @@ ( - z->managed_pages = e1 + atomic_long_set(&z->managed_pages, e1) | - e1->managed_pages++ + atomic_long_inc(&e1->managed_pages) | - z->managed_pages + zone_managed_pages(z) ) @@ expression e,e1; @@ - e->managed_pages += e1 + atomic_long_add(e1, &e->managed_pages) @@ expression z; @@ - z.managed_pages + zone_managed_pages(&z) Then, manually apply following change, include/linux/mmzone.h - unsigned long managed_pages; + atomic_long_t managed_pages; +static inline unsigned long zone_managed_pages(struct zone *zone) +{ + return (unsigned long)atomic_long_read(&zone->managed_pages); +} --- drivers/gpu/drm/amd/amdkfd/kfd_crat.c | 2 +- include/linux/mmzone.h | 9 +++++-- lib/show_mem.c | 2 +- mm/memblock.c | 2 +- mm/page_alloc.c | 44 +++++++++++++++++------------------ mm/vmstat.c | 4 ++-- 6 files changed, 34 insertions(+), 29 deletions(-) diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c index 56412b0..c0e55bb 100644 --- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c +++ b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c @@ -848,7 +848,7 @@ static int kfd_fill_mem_info_for_cpu(int numa_node_id, int *avail_size, */ pgdat = NODE_DATA(numa_node_id); for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) - mem_in_bytes += pgdat->node_zones[zone_type].managed_pages; + mem_in_bytes += zone_managed_pages(&pgdat->node_zones[zone_type]); mem_in_bytes <<= PAGE_SHIFT; sub_type_hdr->length_low = lower_32_bits(mem_in_bytes); diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 847705a..e73dc31 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -435,7 +435,7 @@ struct zone { * adjust_managed_page_count() should be used instead of directly * touching zone->managed_pages and totalram_pages. */ - unsigned long managed_pages; + atomic_long_t managed_pages; unsigned long spanned_pages; unsigned long present_pages; @@ -524,6 +524,11 @@ enum pgdat_flags { PGDAT_RECLAIM_LOCKED, /* prevents concurrent reclaim */ }; +static inline unsigned long zone_managed_pages(struct zone *zone) +{ + return (unsigned long)atomic_long_read(&zone->managed_pages); +} + static inline unsigned long zone_end_pfn(const struct zone *zone) { return zone->zone_start_pfn + zone->spanned_pages; @@ -814,7 +819,7 @@ static inline bool is_dev_zone(const struct zone *zone) */ static inline bool managed_zone(struct zone *zone) { - return zone->managed_pages; + return zone_managed_pages(zone); } /* Returns true if a zone has memory */ diff --git a/lib/show_mem.c b/lib/show_mem.c index 0beaa1d..eefe67d 100644 --- a/lib/show_mem.c +++ b/lib/show_mem.c @@ -28,7 +28,7 @@ void show_mem(unsigned int filter, nodemask_t *nodemask) continue; total += zone->present_pages; - reserved += zone->present_pages - zone->managed_pages; + reserved += zone->present_pages - zone_managed_pages(zone); if (is_highmem_idx(zoneid)) highmem += zone->present_pages; diff --git a/mm/memblock.c b/mm/memblock.c index 7df468c..bbd82ab 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -1950,7 +1950,7 @@ void reset_node_managed_pages(pg_data_t *pgdat) struct zone *z; for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++) - z->managed_pages = 0; + atomic_long_set(&z->managed_pages, 0); } void __init reset_all_zones_managed_pages(void) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 173312b..22e6645 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1279,7 +1279,7 @@ static void __init __free_pages_boot_core(struct page *page, unsigned int order) __ClearPageReserved(p); set_page_count(p, 0); - page_zone(page)->managed_pages += nr_pages; + atomic_long_add(nr_pages, &page_zone(page)->managed_pages); set_page_refcounted(page); __free_pages(page, order); } @@ -2258,7 +2258,7 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone, * Limit the number reserved to 1 pageblock or roughly 1% of a zone. * Check is race-prone but harmless. */ - max_managed = (zone->managed_pages / 100) + pageblock_nr_pages; + max_managed = (zone_managed_pages(zone) / 100) + pageblock_nr_pages; if (zone->nr_reserved_highatomic >= max_managed) return; @@ -4662,7 +4662,7 @@ static unsigned long nr_free_zone_pages(int offset) struct zonelist *zonelist = node_zonelist(numa_node_id(), GFP_KERNEL); for_each_zone_zonelist(zone, z, zonelist, offset) { - unsigned long size = zone->managed_pages; + unsigned long size = zone_managed_pages(zone); unsigned long high = high_wmark_pages(zone); if (size > high) sum += size - high; @@ -4769,7 +4769,7 @@ void si_meminfo_node(struct sysinfo *val, int nid) pg_data_t *pgdat = NODE_DATA(nid); for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) - managed_pages += pgdat->node_zones[zone_type].managed_pages; + managed_pages += zone_managed_pages(&pgdat->node_zones[zone_type]); val->totalram = managed_pages; val->sharedram = node_page_state(pgdat, NR_SHMEM); val->freeram = sum_zone_node_page_state(nid, NR_FREE_PAGES); @@ -4778,7 +4778,7 @@ void si_meminfo_node(struct sysinfo *val, int nid) struct zone *zone = &pgdat->node_zones[zone_type]; if (is_highmem(zone)) { - managed_highpages += zone->managed_pages; + managed_highpages += zone_managed_pages(zone); free_highpages += zone_page_state(zone, NR_FREE_PAGES); } } @@ -4985,7 +4985,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask) K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)), K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)), K(zone->present_pages), - K(zone->managed_pages), + K(zone_managed_pages(zone)), K(zone_page_state(zone, NR_MLOCK)), zone_page_state(zone, NR_KERNEL_STACK_KB), K(zone_page_state(zone, NR_PAGETABLE)), @@ -5645,7 +5645,7 @@ static int zone_batchsize(struct zone *zone) * The per-cpu-pages pools are set to around 1000th of the * size of the zone. */ - batch = zone->managed_pages / 1024; + batch = zone_managed_pages(zone) / 1024; /* But no more than a meg. */ if (batch * PAGE_SIZE > 1024 * 1024) batch = (1024 * 1024) / PAGE_SIZE; @@ -5756,7 +5756,7 @@ static void pageset_set_high_and_batch(struct zone *zone, { if (percpu_pagelist_fraction) pageset_set_high(pcp, - (zone->managed_pages / + (zone_managed_pages(zone) / percpu_pagelist_fraction)); else pageset_set_batch(pcp, zone_batchsize(zone)); @@ -6311,7 +6311,7 @@ static void __meminit pgdat_init_internals(struct pglist_data *pgdat) static void __meminit zone_init_internals(struct zone *zone, enum zone_type idx, int nid, unsigned long remaining_pages) { - zone->managed_pages = remaining_pages; + atomic_long_set(&zone->managed_pages, remaining_pages); zone_set_nid(zone, nid); zone->name = zone_names[idx]; zone->zone_pgdat = NODE_DATA(nid); @@ -7064,7 +7064,7 @@ static int __init cmdline_parse_movablecore(char *p) void adjust_managed_page_count(struct page *page, long count) { spin_lock(&managed_page_count_lock); - page_zone(page)->managed_pages += count; + atomic_long_add(count, &page_zone(page)->managed_pages); totalram_pages += count; #ifdef CONFIG_HIGHMEM if (PageHighMem(page)) @@ -7112,7 +7112,7 @@ void free_highmem_page(struct page *page) { __free_reserved_page(page); totalram_pages++; - page_zone(page)->managed_pages++; + atomic_long_inc(&page_zone(page)->managed_pages); totalhigh_pages++; } #endif @@ -7245,7 +7245,7 @@ static void calculate_totalreserve_pages(void) for (i = 0; i < MAX_NR_ZONES; i++) { struct zone *zone = pgdat->node_zones + i; long max = 0; - unsigned long managed_pages = zone->managed_pages; + unsigned long managed_pages = zone_managed_pages(zone); /* Find valid and maximum lowmem_reserve in the zone */ for (j = i; j < MAX_NR_ZONES; j++) { @@ -7281,7 +7281,7 @@ static void setup_per_zone_lowmem_reserve(void) for_each_online_pgdat(pgdat) { for (j = 0; j < MAX_NR_ZONES; j++) { struct zone *zone = pgdat->node_zones + j; - unsigned long managed_pages = zone->managed_pages; + unsigned long managed_pages = zone_managed_pages(zone); zone->lowmem_reserve[j] = 0; @@ -7299,7 +7299,7 @@ static void setup_per_zone_lowmem_reserve(void) lower_zone->lowmem_reserve[j] = managed_pages / sysctl_lowmem_reserve_ratio[idx]; } - managed_pages += lower_zone->managed_pages; + managed_pages += zone_managed_pages(lower_zone); } } } @@ -7318,14 +7318,14 @@ static void __setup_per_zone_wmarks(void) /* Calculate total number of !ZONE_HIGHMEM pages */ for_each_zone(zone) { if (!is_highmem(zone)) - lowmem_pages += zone->managed_pages; + lowmem_pages += zone_managed_pages(zone); } for_each_zone(zone) { u64 tmp; spin_lock_irqsave(&zone->lock, flags); - tmp = (u64)pages_min * zone->managed_pages; + tmp = (u64)pages_min * zone_managed_pages(zone); do_div(tmp, lowmem_pages); if (is_highmem(zone)) { /* @@ -7339,7 +7339,7 @@ static void __setup_per_zone_wmarks(void) */ unsigned long min_pages; - min_pages = zone->managed_pages / 1024; + min_pages = zone_managed_pages(zone) / 1024; min_pages = clamp(min_pages, SWAP_CLUSTER_MAX, 128UL); zone->watermark[WMARK_MIN] = min_pages; } else { @@ -7356,7 +7356,7 @@ static void __setup_per_zone_wmarks(void) * ensure a minimum size on small systems. */ tmp = max_t(u64, tmp >> 2, - mult_frac(zone->managed_pages, + mult_frac(zone_managed_pages(zone), watermark_scale_factor, 10000)); zone->watermark[WMARK_LOW] = min_wmark_pages(zone) + tmp; @@ -7486,8 +7486,8 @@ static void setup_min_unmapped_ratio(void) pgdat->min_unmapped_pages = 0; for_each_zone(zone) - zone->zone_pgdat->min_unmapped_pages += (zone->managed_pages * - sysctl_min_unmapped_ratio) / 100; + zone->zone_pgdat->min_unmapped_pages += (zone_managed_pages(zone) * + sysctl_min_unmapped_ratio) / 100; } @@ -7514,8 +7514,8 @@ static void setup_min_slab_ratio(void) pgdat->min_slab_pages = 0; for_each_zone(zone) - zone->zone_pgdat->min_slab_pages += (zone->managed_pages * - sysctl_min_slab_ratio) / 100; + zone->zone_pgdat->min_slab_pages += (zone_managed_pages(zone) * + sysctl_min_slab_ratio) / 100; } int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *table, int write, diff --git a/mm/vmstat.c b/mm/vmstat.c index 6038ce5..9fee037 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -227,7 +227,7 @@ int calculate_normal_threshold(struct zone *zone) * 125 1024 10 16-32 GB 9 */ - mem = zone->managed_pages >> (27 - PAGE_SHIFT); + mem = zone_managed_pages(zone) >> (27 - PAGE_SHIFT); threshold = 2 * fls(num_online_cpus()) * (1 + fls(mem)); @@ -1569,7 +1569,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat, high_wmark_pages(zone), zone->spanned_pages, zone->present_pages, - zone->managed_pages); + zone_managed_pages(zone)); seq_printf(m, "\n protection: (%ld", -- 1.9.1
