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![Christoph Lameter](/assets/img/avatar_default.png)
The zone table is mostly not needed. If we have a node in the page flags then we can get to the zone via NODE_DATA() which is much more likely to be already in the cpu cache. In case of SMP and UP NODE_DATA() is a constant pointer which allows us to access an exact replica of zonetable in the node_zones field. In all of the above cases there will be no need at all for the zone table. The only remaining case is if in a NUMA system the node numbers do not fit into the page flags. In that case we make sparse generate a table that maps sections to nodes and use that table to to figure out the node number. This table is sized to fit in a single cache line for the known 32 bit NUMA platform which makes it very likely that the information can be obtained without a cache miss. For sparsemem the zone table seems to be have been fairly large based on the maximum possible number of sections and the number of zones per node. There is some memory saving by removing zone_table. The main benefit is to reduce the cache foootprint of the VM from the frequent lookups of zones. Plus it simplifies the page allocator. [akpm@osdl.org: build fix] Signed-off-by: Christoph Lameter <clameter@sgi.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Andy Whitcroft <apw@shadowen.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
329 lines
7.8 KiB
C
329 lines
7.8 KiB
C
/*
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* sparse memory mappings.
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*/
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <linux/bootmem.h>
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#include <linux/highmem.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/vmalloc.h>
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#include <asm/dma.h>
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/*
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* Permanent SPARSEMEM data:
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*
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* 1) mem_section - memory sections, mem_map's for valid memory
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*/
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#ifdef CONFIG_SPARSEMEM_EXTREME
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struct mem_section *mem_section[NR_SECTION_ROOTS]
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____cacheline_internodealigned_in_smp;
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#else
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struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
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____cacheline_internodealigned_in_smp;
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#endif
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EXPORT_SYMBOL(mem_section);
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#ifdef NODE_NOT_IN_PAGE_FLAGS
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/*
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* If we did not store the node number in the page then we have to
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* do a lookup in the section_to_node_table in order to find which
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* node the page belongs to.
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*/
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#if MAX_NUMNODES <= 256
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static u8 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
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#else
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static u16 section_to_node_table[NR_MEM_SECTIONS] __cacheline_aligned;
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#endif
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unsigned long page_to_nid(struct page *page)
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{
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return section_to_node_table[page_to_section(page)];
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}
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EXPORT_SYMBOL(page_to_nid);
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#endif
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#ifdef CONFIG_SPARSEMEM_EXTREME
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static struct mem_section *sparse_index_alloc(int nid)
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{
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struct mem_section *section = NULL;
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unsigned long array_size = SECTIONS_PER_ROOT *
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sizeof(struct mem_section);
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if (slab_is_available())
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section = kmalloc_node(array_size, GFP_KERNEL, nid);
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else
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section = alloc_bootmem_node(NODE_DATA(nid), array_size);
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if (section)
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memset(section, 0, array_size);
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return section;
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}
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static int sparse_index_init(unsigned long section_nr, int nid)
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{
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static DEFINE_SPINLOCK(index_init_lock);
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unsigned long root = SECTION_NR_TO_ROOT(section_nr);
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struct mem_section *section;
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int ret = 0;
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#ifdef NODE_NOT_IN_PAGE_FLAGS
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section_to_node_table[section_nr] = nid;
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#endif
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if (mem_section[root])
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return -EEXIST;
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section = sparse_index_alloc(nid);
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/*
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* This lock keeps two different sections from
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* reallocating for the same index
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*/
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spin_lock(&index_init_lock);
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if (mem_section[root]) {
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ret = -EEXIST;
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goto out;
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}
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mem_section[root] = section;
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out:
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spin_unlock(&index_init_lock);
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return ret;
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}
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#else /* !SPARSEMEM_EXTREME */
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static inline int sparse_index_init(unsigned long section_nr, int nid)
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{
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return 0;
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}
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#endif
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/*
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* Although written for the SPARSEMEM_EXTREME case, this happens
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* to also work for the flat array case becase
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* NR_SECTION_ROOTS==NR_MEM_SECTIONS.
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*/
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int __section_nr(struct mem_section* ms)
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{
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unsigned long root_nr;
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struct mem_section* root;
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for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) {
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root = __nr_to_section(root_nr * SECTIONS_PER_ROOT);
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if (!root)
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continue;
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if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT)))
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break;
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}
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return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
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}
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/*
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* During early boot, before section_mem_map is used for an actual
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* mem_map, we use section_mem_map to store the section's NUMA
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* node. This keeps us from having to use another data structure. The
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* node information is cleared just before we store the real mem_map.
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*/
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static inline unsigned long sparse_encode_early_nid(int nid)
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{
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return (nid << SECTION_NID_SHIFT);
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}
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static inline int sparse_early_nid(struct mem_section *section)
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{
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return (section->section_mem_map >> SECTION_NID_SHIFT);
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}
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/* Record a memory area against a node. */
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void memory_present(int nid, unsigned long start, unsigned long end)
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{
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unsigned long pfn;
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start &= PAGE_SECTION_MASK;
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for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
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unsigned long section = pfn_to_section_nr(pfn);
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struct mem_section *ms;
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sparse_index_init(section, nid);
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ms = __nr_to_section(section);
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if (!ms->section_mem_map)
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ms->section_mem_map = sparse_encode_early_nid(nid) |
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SECTION_MARKED_PRESENT;
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}
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}
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/*
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* Only used by the i386 NUMA architecures, but relatively
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* generic code.
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*/
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unsigned long __init node_memmap_size_bytes(int nid, unsigned long start_pfn,
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unsigned long end_pfn)
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{
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unsigned long pfn;
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unsigned long nr_pages = 0;
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for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
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if (nid != early_pfn_to_nid(pfn))
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continue;
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if (pfn_valid(pfn))
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nr_pages += PAGES_PER_SECTION;
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}
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return nr_pages * sizeof(struct page);
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}
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/*
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* Subtle, we encode the real pfn into the mem_map such that
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* the identity pfn - section_mem_map will return the actual
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* physical page frame number.
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*/
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static unsigned long sparse_encode_mem_map(struct page *mem_map, unsigned long pnum)
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{
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return (unsigned long)(mem_map - (section_nr_to_pfn(pnum)));
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}
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/*
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* We need this if we ever free the mem_maps. While not implemented yet,
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* this function is included for parity with its sibling.
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*/
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static __attribute((unused))
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struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum)
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{
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return ((struct page *)coded_mem_map) + section_nr_to_pfn(pnum);
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}
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static int sparse_init_one_section(struct mem_section *ms,
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unsigned long pnum, struct page *mem_map)
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{
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if (!valid_section(ms))
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return -EINVAL;
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ms->section_mem_map &= ~SECTION_MAP_MASK;
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ms->section_mem_map |= sparse_encode_mem_map(mem_map, pnum);
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return 1;
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}
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static struct page *sparse_early_mem_map_alloc(unsigned long pnum)
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{
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struct page *map;
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struct mem_section *ms = __nr_to_section(pnum);
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int nid = sparse_early_nid(ms);
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map = alloc_remap(nid, sizeof(struct page) * PAGES_PER_SECTION);
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if (map)
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return map;
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map = alloc_bootmem_node(NODE_DATA(nid),
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sizeof(struct page) * PAGES_PER_SECTION);
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if (map)
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return map;
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printk(KERN_WARNING "%s: allocation failed\n", __FUNCTION__);
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ms->section_mem_map = 0;
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return NULL;
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}
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static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
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{
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struct page *page, *ret;
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unsigned long memmap_size = sizeof(struct page) * nr_pages;
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page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
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if (page)
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goto got_map_page;
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ret = vmalloc(memmap_size);
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if (ret)
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goto got_map_ptr;
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return NULL;
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got_map_page:
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ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
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got_map_ptr:
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memset(ret, 0, memmap_size);
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return ret;
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}
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static int vaddr_in_vmalloc_area(void *addr)
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{
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if (addr >= (void *)VMALLOC_START &&
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addr < (void *)VMALLOC_END)
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return 1;
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return 0;
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}
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static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
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{
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if (vaddr_in_vmalloc_area(memmap))
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vfree(memmap);
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else
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free_pages((unsigned long)memmap,
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get_order(sizeof(struct page) * nr_pages));
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}
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/*
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* Allocate the accumulated non-linear sections, allocate a mem_map
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* for each and record the physical to section mapping.
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*/
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void sparse_init(void)
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{
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unsigned long pnum;
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struct page *map;
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for (pnum = 0; pnum < NR_MEM_SECTIONS; pnum++) {
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if (!valid_section_nr(pnum))
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continue;
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map = sparse_early_mem_map_alloc(pnum);
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if (!map)
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continue;
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sparse_init_one_section(__nr_to_section(pnum), pnum, map);
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}
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}
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/*
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* returns the number of sections whose mem_maps were properly
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* set. If this is <=0, then that means that the passed-in
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* map was not consumed and must be freed.
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*/
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int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
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int nr_pages)
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{
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unsigned long section_nr = pfn_to_section_nr(start_pfn);
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struct pglist_data *pgdat = zone->zone_pgdat;
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struct mem_section *ms;
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struct page *memmap;
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unsigned long flags;
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int ret;
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/*
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* no locking for this, because it does its own
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* plus, it does a kmalloc
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*/
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sparse_index_init(section_nr, pgdat->node_id);
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memmap = __kmalloc_section_memmap(nr_pages);
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pgdat_resize_lock(pgdat, &flags);
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ms = __pfn_to_section(start_pfn);
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if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
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ret = -EEXIST;
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goto out;
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}
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ms->section_mem_map |= SECTION_MARKED_PRESENT;
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ret = sparse_init_one_section(ms, section_nr, memmap);
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out:
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pgdat_resize_unlock(pgdat, &flags);
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if (ret <= 0)
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__kfree_section_memmap(memmap, nr_pages);
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return ret;
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}
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