This patch modifies ia64's show_mem() to walk the vmem_map page tables and
rapidly skip forward across regions where the page tables are missing.
This prevents the pfn_valid() check from causing numerous unnecessary
page faults.
Without this patch on a 512 node 512 cpu system where every node has four
memory holes, the show_mem() call takes 1 hour 18 minutes. With this
patch, it takes less than 3 seconds.
Signed-off-by: Robin Holt <holt@xxxxxxx>
Index: linux-2.6/arch/ia64/mm/discontig.c
===================================================================
--- linux-2.6.orig/arch/ia64/mm/discontig.c 2006-04-12 18:20:44.374700839 -0500
+++ linux-2.6/arch/ia64/mm/discontig.c 2006-04-12 22:11:31.971106982 -0500
@@ -547,8 +547,71 @@ void show_mem(void)
struct page *page;
if (pfn_valid(pgdat->node_start_pfn + i))
page = pfn_to_page(pgdat->node_start_pfn + i);
- else
+ else {
+ /*
+ * At the beginning of a hole. Search vmem_map
+ * page tables for the end.
+ */
+ unsigned long end_address, hole_end_pfn;
+ unsigned long stop_address;
+
+ end_address = (unsigned long) &vmem_map[pgdat->node_start_pfn + i];
+ end_address = PAGE_ALIGN(end_address);
+
+ stop_address = (unsigned long) &vmem_map[
+ pgdat->node_start_pfn + pgdat->node_spanned_pages];
+
+ do {
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ pgd = pgd_offset_k(end_address);
+ if (pgd_none(*pgd)) {
+ end_address += PTRS_PER_PUD *
+ PTRS_PER_PMD *
+ PTRS_PER_PTE *
+ PAGE_SIZE;
+ continue;
+ }
+
+ pud = pud_offset(pgd, end_address);
+ if (pud_none(*pud)) {
+ end_address += PTRS_PER_PMD *
+ PTRS_PER_PTE *
+ PAGE_SIZE;
+ continue;
+ }
+
+ pmd = pmd_offset(pud, end_address);
+ if (pmd_none(*pmd)) {
+ end_address += PTRS_PER_PTE *
+ PAGE_SIZE;
+ continue;
+ }
+
+ pte = pte_offset_kernel(pmd, end_address);
+
+retry_pte:
+ if (pte_none(*pte)) {
+ end_address += PAGE_SIZE;
+ pte++;
+ if ((end_address < stop_address) &&
+ (end_address != ALIGN(end_address, 1UL << PMD_SHIFT)))
+ goto retry_pte;
+ continue;
+ }
+ /* Found next valid vmem_map page */
+ break;
+ } while (end_address < stop_address);
+
+ end_address = end_address - (unsigned long) vmem_map - 1;
+ hole_end_pfn = end_address / sizeof(struct page);
+ i = hole_end_pfn - pgdat->node_start_pfn;
+
continue;
+ }
if (PageReserved(page))
reserved++;
else if (PageSwapCache(page))
-
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