linux-kernel - RE: [PATCH 2/2] thp: support split page table lock

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Message-ID: <87y577gsle.fsf@linux.vnet.ibm.com>
Date:	Sun, 08 Sep 2013 22:26:29 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Andi Kleen <andi@...stfloor.org>,
	Michal Hocko <mhocko@...e.cz>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	kirill.shutemov@...ux.intel.com, Alex Thorlton <athorlton@....com>,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH 2/2] thp: support split page table lock

"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> writes:

> Naoya Horiguchi wrote:
>> Thp related code also uses per process mm->page_table_lock now.
>> So making it fine-grained can provide better performance.
>> 
>> This patch makes thp support split page table lock by using page->ptl
>> of the pages storing "pmd_trans_huge" pmds.
>> 
>> Some functions like pmd_trans_huge_lock() and page_check_address_pmd()
>> are expected by their caller to pass back the pointer of ptl, so this
>> patch adds to those functions new arguments for that. Rather than that,
>> this patch gives only straightforward replacement.
>> 
>> ChangeLog v3:
>>  - fixed argument of huge_pmd_lockptr() in copy_huge_pmd()
>>  - added missing declaration of ptl in do_huge_pmd_anonymous_page()
>> 
>> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
>
> Generally, looks good. Few notes:
>
> I believe you need to convert __pte_alloc() to new locking. Not sure about
> __pte_alloc_kernel().
> Have you check all rest mm->page_table_lock, that they shouldn't be
> converted to new locking?

May be we can have a CONFIG_DEBUG_VM version of pmd_populate that check 
check with assert_spin_locked ?


-aneesh

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