Messages in this thread Patch in this message | | | Date | Thu, 26 Aug 2004 20:58:06 +0900 | From | Hiroyuki KAMEZAWA <> | Subject | [RFC] buddy allocator without bitmap [1/4] |
| |
This is 2nd part of patches, for zone initialization.
New member, zone->aligned_order and zone->nr_mem_map is added to zone.
aligned_order indicates memmap is aligned below this order. nr_mem_map indicates memmap is diveded into nr_mem_map.
How these works ? prease see patch 4th ;), there are used to coalesce pages.
-- Kame
================== This patch removes bitmap allocation in zone_init_free_lists() and page_to_bitmap_size();
And new added member zone->aligned_order is initialized.
zone->alined_order guarantees "zone is aligned to (1 << zone->aligned_order) contiguous pages"
If zone->alined_order == MAX_ORDER, zone is completely aligned, and every page is guaranteed to have its buddy page in any order.
zone->aligned_order is used in free_pages_bulk() to skip range checking. By using this, if order < zone->aligned_order, we do not have to worry about "a page can have its buddy in an order or not?"
This would work well in several architectures.
But my ia64 box shows zone->aligned_order=0 .....this aligned_order would not be helpful in some environment.
-- Kame
---
linux-2.6.8.1-mm4-kame-kamezawa/mm/page_alloc.c | 78 +++++++++++------------- 1 files changed, 38 insertions(+), 40 deletions(-)
diff -puN mm/page_alloc.c~eliminate-bitmap-init mm/page_alloc.c --- linux-2.6.8.1-mm4-kame/mm/page_alloc.c~eliminate-bitmap-init 2004-08-26 08:42:33.572192352 +0900 +++ linux-2.6.8.1-mm4-kame-kamezawa/mm/page_alloc.c 2004-08-26 08:42:33.577191592 +0900 @@ -1499,6 +1499,30 @@ static void __init calculate_zone_totalp printk(KERN_DEBUG "On node %d totalpages: %lu\n", pgdat->node_id, realtotalpages); }
+/* + * calculate_aligned_order() + * this function calculates an upper bound order of alignment + * of buddy pages. if order < zone->aligned_order, every page + * are guaranteed to have its buddy. + */ +void __init calculate_aligned_order(struct zone *zone, + unsigned long start_pfn, + unsigned long nr_pages) +{ + int order, page_idx; + unsigned long mask; + + page_idx = start_pfn - zone->zone_start_pfn; + + for (order = 0 ; order < MAX_ORDER; order++) { + mask = 1UL << order; + if ((page_idx & mask) || (nr_pages & mask)) + break; + } + if (order < zone->aligned_order) + zone->aligned_order = order; + printk("Aligned order of %s is %d \n",zone->name, zone->aligned_order); +}
/* * Initially all pages are reserved - free ones are freed @@ -1510,7 +1534,9 @@ void __init memmap_init_zone(unsigned lo { struct page *start = pfn_to_page(start_pfn); struct page *page; - + unsigned long saved_start_pfn = start_pfn; + struct zone *zonep = zone_table[NODEZONE(nid, zone)]; + for (page = start; page < (start + size); page++) { set_page_zone(page, NODEZONE(nid, zone)); set_page_count(page, 0); @@ -1524,51 +1550,20 @@ void __init memmap_init_zone(unsigned lo #endif start_pfn++; } -} - -/* - * Page buddy system uses "index >> (i+1)", where "index" is - * at most "size-1". - * - * The extra "+3" is to round down to byte size (8 bits per byte - * assumption). Thus we get "(size-1) >> (i+4)" as the last byte - * we can access. - * - * The "+1" is because we want to round the byte allocation up - * rather than down. So we should have had a "+7" before we shifted - * down by three. Also, we have to add one as we actually _use_ the - * last bit (it's [0,n] inclusive, not [0,n[). - * - * So we actually had +7+1 before we shift down by 3. But - * (n+8) >> 3 == (n >> 3) + 1 (modulo overflows, which we do not have). - * - * Finally, we LONG_ALIGN because all bitmap operations are on longs. - */ -unsigned long pages_to_bitmap_size(unsigned long order, unsigned long nr_pages) -{ - unsigned long bitmap_size; - - bitmap_size = (nr_pages-1) >> (order+4); - bitmap_size = LONG_ALIGN(bitmap_size+1); - - return bitmap_size; + /* Because memmap_init_zone() is called in suitable way + * even if zone has memory holes, + * calling calculate_aligned_order(zone) here is reasonable + */ + calculate_aligned_order(zonep, saved_start_pfn, size); + + zonep->nr_mem_map++; }
void zone_init_free_lists(struct pglist_data *pgdat, struct zone *zone, unsigned long size) { int order; - for (order = 0; ; order++) { - unsigned long bitmap_size; - + for (order = 0 ; order < MAX_ORDER ; order++) { INIT_LIST_HEAD(&zone->free_area[order].free_list); - if (order == MAX_ORDER-1) { - zone->free_area[order].map = NULL; - break; - } - - bitmap_size = pages_to_bitmap_size(order, size); - zone->free_area[order].map = - (unsigned long *) alloc_bootmem_node(pgdat, bitmap_size); } }
@@ -1682,6 +1677,9 @@ static void __init free_area_init_core(s if ((zone_start_pfn) & (zone_required_alignment-1)) printk("BUG: wrong zone alignment, it will crash\n");
+ zone->aligned_order = MAX_ORDER; + zone->nr_mem_map = 0; + memmap_init(size, nid, j, zone_start_pfn);
zone_start_pfn += size; _
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |