Robin Holt wrote: [Thu Apr 13 2006, 09:14:42AM EDT]
>
> 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>
>
> ---
> Fixed.
>
>
> Index: linux-2.6/arch/ia64/mm/discontig.c
> ===================================================================
> --- linux-2.6.orig/arch/ia64/mm/discontig.c 2006-04-13 06:16:00.500029306 -0500
> +++ linux-2.6/arch/ia64/mm/discontig.c 2006-04-13 07:01:31.668069891 -0500
> @@ -519,6 +519,69 @@ void __cpuinit *per_cpu_init(void)
> }
> #endif /* CONFIG_SMP */
How about these changes to fix SPARSEMEM.
>
> +
#ifdef CONFIG_VIRTUAL_MEM_MAP
> +static 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 += 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 = 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
This should optimize out below for SPARSEMEM.
bob
> +
> +
> /**
> * show_mem - give short summary of memory stats
> *
> @@ -547,8 +610,10 @@ 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))
-
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