Re: [PATCH v2 20/20] x86, mm, numa: Put pagetable on local node ram for 64bit

Tang Chen
2013-03-11T05:47:17Z

Hi Yinghai,

Please see below. :)

On 03/10/2013 02:44 PM, Yinghai Lu wrote:
> If node with ram is hotplugable, local node mem for page table and vmemmap
> should be on that node ram.
>
> This patch is some kind of refreshment of
> | commit 1411e0ec3123ae4c4ead6bfc9fe3ee5a3ae5c327
> | Date: Mon Dec 27 16:48:17 2010 -0800
> |
> | x86-64, numa: Put pgtable to local node memory
> That was reverted before.
>
> We have reason to reintroduce it to make memory hotplug work.
>
> Calling init_mem_mapping in early_initmem_init for every node.
> alloc_low_pages will alloc page table in following order:
> BRK, local node, low range
> So page table will be on low range or local nodes.
>
> Signed-off-by: Yinghai Lu<yinghai@kernel.org>
> Cc: Pekka Enberg<penberg@kernel.org>
> Cc: Jacob Shin<jacob.shin@amd.com>
> Cc: Konrad Rzeszutek Wilk<konrad.wilk@oracle.com>
> ---
> arch/x86/mm/numa.c | 34 +++++++++++++++++++++++++++++++++-
> 1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index d3eb0c9..11acdf6 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -673,7 +673,39 @@ static void __init early_x86_numa_init(void)
> #ifdef CONFIG_X86_64
> static void __init early_x86_numa_init_mapping(void)
> {
> - init_mem_mapping(0, max_pfn<< PAGE_SHIFT);
> + unsigned long last_start = 0, last_end = 0;
> + struct numa_meminfo *mi =&numa_meminfo;
> + unsigned long start, end;
> + int last_nid = -1;
> + int i, nid;
> +
> + for (i = 0; i< mi->nr_blks; i++) {
> + nid = mi->blk[i].nid;
> + start = mi->blk[i].start;
> + end = mi->blk[i].end;
> +
> + if (last_nid == nid) {
> + last_end = end;
> + continue;
> + }
> +
> + /* other nid now */
> + if (last_nid>= 0) {
> + printk(KERN_DEBUG "Node %d: [mem %#016lx-%#016lx]\n",
> + last_nid, last_start, last_end - 1);
> + init_mem_mapping(last_start, last_end);

IIUC, we call init_mem_mapping() for each node ranges. In the first time,
local_max_pfn_mapped = begin >> PAGE_SHIFT;
local_min_pfn_mapped = real_end >> PAGE_SHIFT;
which means
local_min_pfn_mapped >= local_max_pfn_mapped
right ?

So, the first page allocated by alloc_low_pages() is not on local node,
right ?
Furthermore, the first page of pagetable is not on local node, right ?

BTW, I'm reading your code, and doing necessary hot-add and hot-remove
changes now.

Thanks. :)

> + }
> +
> + /* for next nid */
> + last_nid = nid;
> + last_start = start;
> + last_end = end;
> + }
> + /* last one */
> + printk(KERN_DEBUG "Node %d: [mem %#016lx-%#016lx]\n",
> + last_nid, last_start, last_end - 1);
> + init_mem_mapping(last_start, last_end);
> +
> if (max_pfn> max_low_pfn)
> max_low_pfn = max_pfn;
> }