On Thu, Mar 30, 2006 at 09:48:18AM -0800, Chen, Kenneth W wrote:
> Jack Steiner wrote on Thursday, March 30, 2006 9:29 AM
> > > Time is wasted trying to fill the TLB entry for the vmem_map. When it
> > > fails, we show_mem() advances to the next page which repeats the sequence.
> > > Jack had thrown out a couple suggestions. One was essentially what
> > > you proposed below. The other was advance i to point the next page
> > > of pfns. He frowned when saying the second, but I don't recall exactly
> > > why he frowned.
> >
> > Advancing to the next page will be considerably faster but I wonder if
> > it is fast enough.
> >
...
> > My gut feeling is that is not good enough.
>
> What about the earlier proposal of advancing at pmd and pud granule by
> walking the page table? There it can walk at 32MB/64GB step.
Does the attached seem like the right direction? I have tested it on
the simulator and it seems _much_ faster, but that is the simulator.
I have time reserved on the machine where the problem was first observed
later today to test it on actual hardware.
Thanks,
Robin
Index: linux-2.6/arch/ia64/mm/discontig.c
===================================================================
--- linux-2.6.orig/arch/ia64/mm/discontig.c 2006-04-11 16:06:54.243967238 -0500
+++ linux-2.6/arch/ia64/mm/discontig.c 2006-04-12 02:16:46.111406150 -0500
@@ -567,8 +567,68 @@ 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 for the end. */
+ unsigned long end_address, next_page_offset;
+ 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];
+
+ /* walk vmem_map page tables until valid pfn found */
+ 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;
+ next_page_offset = ALIGN(end_address, sizeof(struct page));
+ i = next_page_offset / sizeof(struct page) - pgdat->node_start_pfn;
+
continue;
+ }
if (PageReserved(page))
reserved++;
else if (PageSwapCache(page))
-
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