linux-kernel - Re: THP: AnonHugePages in /proc/[pid]/smaps is correct or not?

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Message-ID: <515B70A1.3040200@gmail.com>
Date:	Wed, 03 Apr 2013 07:58:25 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Zhouping Liu <zliu@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Amos Kong <akong@...hat.com>
Subject: Re: THP: AnonHugePages in /proc/[pid]/smaps is correct or not?

Hi David,
On 04/03/2013 02:09 AM, David Rientjes wrote:
> On Tue, 2 Apr 2013, Simon Jeons wrote:
>
>> Both thp and hugetlb pages should be 2MB aligned, correct?
>>
> To answer this question and your followup reply at the same time: they
> come from one level higher in the page table so they will naturally need
> to be 2MB aligned.

When I hacking arch/x86/mm/hugetlbpage.c like this,
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index ae1aa71..87f34ee 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -354,14 +354,13 @@ hugetlb_get_unmapped_area(struct file *file,
unsigned long addr,

#endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/

-#ifdef CONFIG_X86_64
static __init int setup_hugepagesz(char *opt)
{
unsigned long ps = memparse(opt, &opt);
if (ps == PMD_SIZE) {
hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
- } else if (ps == PUD_SIZE && cpu_has_gbpages) {
- hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
+ } else if (ps == PUD_SIZE) {
+ hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT+4);
} else {
printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
ps >> 20);

I set boot=hugepagesz=1G hugepages=10, then I got 10 32MB huge pages.
What's the difference between these pages which I hacking and normal
huge pages?
--
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