[IA64] Make show_mem() skip holes in a pgdat

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@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
index ec9eeb89975d6c3c4952bdea4ca4511e12e465a5..b6bcc9fa36030690b073440781e48398847ae547 100644 (file)
--- a/arch/ia64/mm/discontig.c
+++ b/arch/ia64/mm/discontig.c
@@ -519,6 +519,68 @@ void __cpuinit *per_cpu_init(void)
 }
 #endif /* CONFIG_SMP */
 
+#ifdef CONFIG_VIRTUAL_MEM_MAP
+static inline int find_next_valid_pfn_for_pgdat(pg_data_t *pgdat, int i)
+{
+       unsigned long end_address, hole_next_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 += PGDIR_SIZE;
+                       continue;
+               }
+
+               pud = pud_offset(pgd, end_address);
+               if (pud_none(*pud)) {
+                       end_address += PUD_SIZE;
+                       continue;
+               }
+
+               pmd = pmd_offset(pud, end_address);
+               if (pmd_none(*pmd)) {
+                       end_address += PMD_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 = min(end_address, stop_address);
+       end_address = end_address - (unsigned long) vmem_map + sizeof(struct page) - 1;
+       hole_next_pfn = end_address / sizeof(struct page);
+       return hole_next_pfn - pgdat->node_start_pfn;
+}
+#else
+static inline int find_next_valid_pfn_for_pgdat(pg_data_t *pgdat, int i)
+{
+       return i + 1;
+}
+#endif
+
 /**
  * show_mem - give short summary of memory stats
  *
@@ -547,8 +609,10 @@ 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 {
+                               i = find_next_valid_pfn_for_pgdat(pgdat, i) - 1;
                                continue;
+                       }
                        if (PageReserved(page))
                                reserved++;
                        else if (PageSwapCache(page))