linux-kernel - Re: [PATCH v4 3/3] memcg: avoid THP split in task migration

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Date:	Tue, 13 Mar 2012 14:47:36 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Hillf Danton <dhillf@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v4 3/3] memcg: avoid THP split in task migration

On Mon, 12 Mar 2012 18:30:56 -0400
Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:

> Currently we can't do task migration among memory cgroups without THP split,
> which means processes heavily using THP experience large overhead in task
> migration. This patch introduces the code for moving charge of THP and makes
> THP more valuable.
> 
> Changes from v3:
> - use enum mc_target_type and MC_TARGET_* explicitly
> - replace lengthy name is_target_thp_for_mc() with get_mctgt_type_thp()
> - drop cond_resched()
> - drop mapcount check of page sharing (Hugh and KAMEZAWA-san are preparing
>   patches to change the behavior of moving charge of shared pages, so this
>   patch keeps up with the change to avoid potential conflict.)
> 
> Changes from v2:
> - add move_anon() and mapcount check
> 
> Changes from v1:
> - rename is_target_huge_pmd_for_mc() to is_target_thp_for_mc()
> - remove pmd_present() check (it's buggy when pmd_trans_huge(pmd) is true)
> - is_target_thp_for_mc() calls get_page() only when checks are passed
> - unlock page table lock if !mc.precharge
> - compare return value of is_target_thp_for_mc() explicitly to MC_TARGET_TYPE
> - clean up &walk->mm->page_table_lock to &vma->vm_mm->page_table_lock
> - add comment about why race with split_huge_page() does not happen
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Acked-by: Hillf Danton <dhillf@...il.com>

Thank you.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


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