linux-kernel - Re: [PATCH 2/2] mm: thp: give transparent hugepage code a separate copy

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Date:	Tue, 05 Nov 2013 10:47:03 -0800
From:	Dave Hansen <dave@...1.net>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	dave.jiang@...el.com, Mel Gorman <mgorman@...e.de>,
	akpm@...ux-foundation.org, dhillf@...il.com
Subject: Re: [PATCH 2/2] mm: thp: give transparent hugepage code a separate
 copy_page

On 10/28/2013 03:11 PM, Kirill A. Shutemov wrote:
> On Mon, Oct 28, 2013 at 03:16:20PM -0700, Dave Hansen wrote:
>> void copy_huge_page(struct page *dst, struct page *src)
>> {
>>         struct hstate *h = page_hstate(src);
>>         if (unlikely(pages_per_huge_page(h) > MAX_ORDER_NR_PAGES)) {
>> ...
>>
>> This patch creates a copy_high_order_page() which can
>> be used on THP pages.
> 
> We already have copy_user_huge_page() and copy_user_gigantic_page() in
> generic code (mm/memory.c). I think copy_gigantic_page() and
> copy_huge_page() should be moved there too.

That would be fine I guesss... in another patch. :)

> BTW, I think pages_per_huge_page in copy_user_huge_page() is redunand:
> compound_order(page) should be enough, right?

The way it is now, the compiler can optimize for the !HUGETLBFS case.
Also, pages_per_huge_page() works for gigantic pages.  compound_order()
wouldn't work for those.

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