This patch was inspired by the discussion of this problem: http://lkml.kernel.org/r/20180130083006.GB1245@xxxxxxxxxx Currently, during memory hotplugging we traverse struct pages several times: 1. memset(0) in sparse_add_one_section() 2. loop in __add_section() to set do: set_page_node(page, nid); and SetPageReserved(page); 3. loop in pages_correctly_reserved() to check that SetPageReserved is set. 4. loop in memmap_init_zone() to call __init_single_pfn() This patch removes loops 1, 2, and 3 and only leaves the loop 4, where all struct page fields are initialized in one go, the same as it is now done during boot. The benefits: - We improve the memory hotplug performance because we are not evicting cache several times and also reduce loop branching overheads. - Remove condition from hotpath in __init_single_pfn(), that was added in order to fix the problem that was reported by Bharata in the above email thread, thus also improve the performance during normal boot. - Make memory hotplug more similar to boot memory initialization path because we zero and initialize struct pages only in one function. - Simplifies memory hotplug strut page initialization code, and thus enables future improvements, such as multi-threading the initialization of struct pages in order to improve the hotplug performance even further on larger machines. Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> --- drivers/base/memory.c | 36 ++++++++++++++++++++---------------- include/linux/memory_hotplug.h | 2 ++ mm/memory_hotplug.c | 21 ++------------------- mm/page_alloc.c | 28 ++++++++++------------------ mm/sparse.c | 28 +++++++++++++++++++++++++--- 5 files changed, 59 insertions(+), 56 deletions(-) diff --git a/drivers/base/memory.c b/drivers/base/memory.c index fe4b24f05f6a..deb3f029b451 100644 --- a/drivers/base/memory.c +++ b/drivers/base/memory.c @@ -187,13 +187,14 @@ int memory_isolate_notify(unsigned long val, void *v) } /* - * The probe routines leave the pages reserved, just as the bootmem code does. - * Make sure they're still that way. + * The probe routines leave the pages uninitialized, just as the bootmem code + * does. Make sure we do not access them, but instead use only information from + * within sections. */ -static bool pages_correctly_reserved(unsigned long start_pfn) +static bool pages_correctly_probed(unsigned long start_pfn) { - int i, j; - struct page *page; + unsigned long section_nr = pfn_to_section_nr(start_pfn); + unsigned long section_nr_end = section_nr + sections_per_block; unsigned long pfn = start_pfn; /* @@ -201,21 +202,24 @@ static bool pages_correctly_reserved(unsigned long start_pfn) * SPARSEMEM_VMEMMAP. We lookup the page once per section * and assume memmap is contiguous within each section */ - for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) { + for (; section_nr < section_nr_end; section_nr++) { if (WARN_ON_ONCE(!pfn_valid(pfn))) return false; - page = pfn_to_page(pfn); - - for (j = 0; j < PAGES_PER_SECTION; j++) { - if (PageReserved(page + j)) - continue; - - printk(KERN_WARNING "section number %ld page number %d " - "not reserved, was it already online?\n", - pfn_to_section_nr(pfn), j); + if (!present_section_nr(section_nr)) { + pr_warn("section %ld pfn[%lx, %lx) not present", + section_nr, pfn, pfn + PAGES_PER_SECTION); + return false; + } else if (!valid_section_nr(section_nr)) { + pr_warn("section %ld pfn[%lx, %lx) no valid memmap", + section_nr, pfn, pfn + PAGES_PER_SECTION); + return false; + } else if (online_section_nr(section_nr)) { + pr_warn("section %ld pfn[%lx, %lx) is already online", + section_nr, pfn, pfn + PAGES_PER_SECTION); return false; } + pfn += PAGES_PER_SECTION; } return true; @@ -237,7 +241,7 @@ memory_block_action(unsigned long phys_index, unsigned long action, int online_t switch (action) { case MEM_ONLINE: - if (!pages_correctly_reserved(start_pfn)) + if (!pages_correctly_probed(start_pfn)) return -EBUSY; ret = online_pages(start_pfn, nr_pages, online_type); diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 787411bdeadb..13acf181fb4b 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -234,6 +234,8 @@ void put_online_mems(void); void mem_hotplug_begin(void); void mem_hotplug_done(void); +int get_section_nid(unsigned long section_nr); + #else /* ! CONFIG_MEMORY_HOTPLUG */ #define pfn_to_online_page(pfn) \ ({ \ diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 6a9bee33ffa7..e7d11a14b1d1 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -250,7 +250,6 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn, struct vmem_altmap *altmap, bool want_memblock) { int ret; - int i; if (pfn_valid(phys_start_pfn)) return -EEXIST; @@ -259,23 +258,6 @@ static int __meminit __add_section(int nid, unsigned long phys_start_pfn, if (ret < 0) return ret; - /* - * Make all the pages reserved so that nobody will stumble over half - * initialized state. - * FIXME: We also have to associate it with a node because page_to_nid - * relies on having page with the proper node. - */ - for (i = 0; i < PAGES_PER_SECTION; i++) { - unsigned long pfn = phys_start_pfn + i; - struct page *page; - if (!pfn_valid(pfn)) - continue; - - page = pfn_to_page(pfn); - set_page_node(page, nid); - SetPageReserved(page); - } - if (!want_memblock) return 0; @@ -913,7 +895,8 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ int ret; struct memory_notify arg; - nid = pfn_to_nid(pfn); + nid = get_section_nid(pfn_to_section_nr(pfn)); + /* associate pfn range with the zone */ zone = move_pfn_range(online_type, nid, pfn, nr_pages); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e2b42f603b1a..b26991867393 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1178,10 +1178,9 @@ static void free_one_page(struct zone *zone, } static void __meminit __init_single_page(struct page *page, unsigned long pfn, - unsigned long zone, int nid, bool zero) + unsigned long zone, int nid) { - if (zero) - mm_zero_struct_page(page); + mm_zero_struct_page(page); set_page_links(page, zone, nid, pfn); init_page_count(page); page_mapcount_reset(page); @@ -1195,12 +1194,6 @@ static void __meminit __init_single_page(struct page *page, unsigned long pfn, #endif } -static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone, - int nid, bool zero) -{ - return __init_single_page(pfn_to_page(pfn), pfn, zone, nid, zero); -} - #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT static void __meminit init_reserved_page(unsigned long pfn) { @@ -1219,7 +1212,7 @@ static void __meminit init_reserved_page(unsigned long pfn) if (pfn >= zone->zone_start_pfn && pfn < zone_end_pfn(zone)) break; } - __init_single_pfn(pfn, zid, nid, true); + __init_single_page(pfn_to_page(pfn), pfn, zone, nid); } #else static inline void init_reserved_page(unsigned long pfn) @@ -1536,7 +1529,7 @@ static unsigned long __init deferred_init_pages(int nid, int zid, } else { page++; } - __init_single_page(page, pfn, zid, nid, true); + __init_single_page(page, pfn, zid, nid); nr_pages++; } return (nr_pages); @@ -5329,6 +5322,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, pg_data_t *pgdat = NODE_DATA(nid); unsigned long pfn; unsigned long nr_initialised = 0; + struct page *page; #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP struct memblock_region *r = NULL, *tmp; #endif @@ -5390,6 +5384,11 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, #endif not_early: + page = pfn_to_page(pfn); + __init_single_page(page, pfn, zone, nid); + if (context == MEMMAP_HOTPLUG) + SetPageReserved(page); + /* * Mark the block movable so that blocks are reserved for * movable at startup. This will force kernel allocations @@ -5406,15 +5405,8 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, * because this is done early in sparse_add_one_section */ if (!(pfn & (pageblock_nr_pages - 1))) { - struct page *page = pfn_to_page(pfn); - - __init_single_page(page, pfn, zone, nid, - context != MEMMAP_HOTPLUG); set_pageblock_migratetype(page, MIGRATE_MOVABLE); cond_resched(); - } else { - __init_single_pfn(pfn, zone, nid, - context != MEMMAP_HOTPLUG); } } } diff --git a/mm/sparse.c b/mm/sparse.c index 7af5e7a92528..11ed21fb52b0 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -30,11 +30,14 @@ struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT] #endif EXPORT_SYMBOL(mem_section); -#ifdef NODE_NOT_IN_PAGE_FLAGS +#if defined(NODE_NOT_IN_PAGE_FLAGS) || defined(CONFIG_MEMORY_HOTPLUG) /* * If we did not store the node number in the page then we have to * do a lookup in the section_to_node_table in order to find which * node the page belongs to. + * + * We also use this data in case memory hotplugging is enabled to be + * able to determine nid while struct pages are not yet initialized. */ #if MAX_NUMNODES <= 256 static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned; @@ -42,17 +45,28 @@ static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned; static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned; #endif +#ifdef NODE_NOT_IN_PAGE_FLAGS int page_to_nid(const struct page *page) { return section_to_node_table[page_to_section(page)]; } EXPORT_SYMBOL(page_to_nid); +#endif /* NODE_NOT_IN_PAGE_FLAGS */ static void set_section_nid(unsigned long section_nr, int nid) { section_to_node_table[section_nr] = nid; } -#else /* !NODE_NOT_IN_PAGE_FLAGS */ + +/* Return NID for given section number */ +int get_section_nid(unsigned long section_nr) +{ + if (WARN_ON(section_nr >= NR_MEM_SECTIONS)) + return 0; + return section_to_node_table[section_nr]; +} +EXPORT_SYMBOL(get_section_nid); +#else /* ! (NODE_NOT_IN_PAGE_FLAGS || CONFIG_MEMORY_HOTPLUG) */ static inline void set_section_nid(unsigned long section_nr, int nid) { } @@ -816,7 +830,13 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat, goto out; } - memset(memmap, 0, sizeof(struct page) * PAGES_PER_SECTION); +#ifdef CONFIG_DEBUG_VM_PGFLAGS + /* + * poison uninitialized struct pages in order to catch invalid flags + * combinations. + */ + memset(memmap, -1, sizeof(struct page) * PAGES_PER_SECTION); +#endif section_mark_present(ms); @@ -827,6 +847,8 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat, if (ret <= 0) { kfree(usemap); __kfree_section_memmap(memmap, altmap); + } else { + set_section_nid(section_nr, pgdat->node_id); } return ret; } -- 2.16.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
