Commit ace1d816 authored by Robin Holt's avatar Robin Holt Committed by Tony Luck
Browse files

[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: default avatarRobin Holt <holt@sgi.com>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 356a5c1c

arch/ia64/mm/discontig.c

+65 −1
Original line number Diff line number Diff line
@@ -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))

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