![Christoph Lameter](/assets/img/avatar_default.png)
SPARSEMEM is a pretty nice framework that unifies quite a bit of code over all the arches. It would be great if it could be the default so that we can get rid of various forms of DISCONTIG and other variations on memory maps. So far what has hindered this are the additional lookups that SPARSEMEM introduces for virt_to_page and page_address. This goes so far that the code to do this has to be kept in a separate function and cannot be used inline. This patch introduces a virtual memmap mode for SPARSEMEM, in which the memmap is mapped into a virtually contigious area, only the active sections are physically backed. This allows virt_to_page page_address and cohorts become simple shift/add operations. No page flag fields, no table lookups, nothing involving memory is required. The two key operations pfn_to_page and page_to_page become: #define __pfn_to_page(pfn) (vmemmap + (pfn)) #define __page_to_pfn(page) ((page) - vmemmap) By having a virtual mapping for the memmap we allow simple access without wasting physical memory. As kernel memory is typically already mapped 1:1 this introduces no additional overhead. The virtual mapping must be big enough to allow a struct page to be allocated and mapped for all valid physical pages. This vill make a virtual memmap difficult to use on 32 bit platforms that support 36 address bits. However, if there is enough virtual space available and the arch already maps its 1-1 kernel space using TLBs (f.e. true of IA64 and x86_64) then this technique makes SPARSEMEM lookups even more efficient than CONFIG_FLATMEM. FLATMEM needs to read the contents of the mem_map variable to get the start of the memmap and then add the offset to the required entry. vmemmap is a constant to which we can simply add the offset. This patch has the potential to allow us to make SPARSMEM the default (and even the only) option for most systems. It should be optimal on UP, SMP and NUMA on most platforms. Then we may even be able to remove the other memory models: FLATMEM, DISCONTIG etc. [apw@shadowen.org: config cleanups, resplit code etc] [kamezawa.hiroyu@jp.fujitsu.com: Fix sparsemem_vmemmap init] [apw@shadowen.org: vmemmap: remove excess debugging] [apw@shadowen.org: simplify initialisation code and reduce duplication] [apw@shadowen.org: pull out the vmemmap code into its own file] Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andy Whitcroft <apw@shadowen.org> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Andi Kleen <ak@suse.de> Cc: "David S. Miller" <davem@davemloft.net> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
363 lines
8.6 KiB
C
363 lines
8.6 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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#include <asm/pgalloc.h>
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#include <asm/pgtable.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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int 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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static void set_section_nid(unsigned long section_nr, int nid)
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{
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section_to_node_table[section_nr] = nid;
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}
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#else /* !NODE_NOT_IN_PAGE_FLAGS */
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static inline void set_section_nid(unsigned long section_nr, int nid)
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{
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}
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#endif
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#ifdef CONFIG_SPARSEMEM_EXTREME
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static struct mem_section noinline __init_refok *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 __meminit 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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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 because
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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 __init 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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set_section_nid(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_present(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 __meminit 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 (!present_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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SECTION_HAS_MEM_MAP;
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return 1;
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}
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__attribute__((weak)) __init
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void *alloc_bootmem_high_node(pg_data_t *pgdat, unsigned long size)
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{
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return NULL;
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}
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#ifndef CONFIG_SPARSEMEM_VMEMMAP
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struct page __init *sparse_early_mem_map_populate(unsigned long pnum, int nid)
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{
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struct page *map;
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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_high_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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map = alloc_bootmem_node(NODE_DATA(nid),
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sizeof(struct page) * PAGES_PER_SECTION);
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return map;
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}
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#endif /* !CONFIG_SPARSEMEM_VMEMMAP */
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struct page __init *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 = sparse_early_mem_map_populate(pnum, nid);
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if (map)
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return map;
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printk(KERN_ERR "%s: sparsemem memory map backing failed "
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"some memory will not be available.\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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/*
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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 __init 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 (!present_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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#ifdef CONFIG_MEMORY_HOTPLUG
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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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* 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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#endif
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