linux-kernel - Re: [PATCH 0/3] mm, thp: remove duplication and fix locking issues in swapin

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Date:	Fri, 27 May 2016 15:12:47 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Ebru Akagunduz <ebru.akagunduz@...il.com>
Cc:	linux-mm@...ck.org, hughd@...gle.com, riel@...hat.com,
	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	n-horiguchi@...jp.nec.com, aarcange@...hat.com,
	iamjoonsoo.kim@....com, gorcunov@...nvz.org,
	linux-kernel@...r.kernel.org, mgorman@...e.de, rientjes@...gle.com,
	vbabka@...e.cz, aneesh.kumar@...ux.vnet.ibm.com,
	hannes@...xchg.org, boaz@...xistor.com
Subject: Re: [PATCH 0/3] mm, thp: remove duplication and fix locking issues
 in swapin

On Mon 23-05-16 20:29:29, Ebru Akagunduz wrote:
> On Mon, May 23, 2016 at 08:14:08PM +0300, Ebru Akagunduz wrote:
> > This patch series removes duplication of included header
> > and fixes locking inconsistency in khugepaged swapin
> > 
> > Ebru Akagunduz (3):
> >   mm, thp: remove duplication of included header
> >   mm, thp: fix possible circular locking dependency caused by
> >     sum_vm_event()
> >   mm, thp: make swapin readahead under down_read of mmap_sem
> > 
> >  mm/huge_memory.c | 39 ++++++++++++++++++++++++++++++---------
> >  1 file changed, 30 insertions(+), 9 deletions(-)
> > 
> 
> Hi Andrew,
> 
> I prepared this patch series to solve rest of
> problems of khugepaged swapin.
> 
> I have seen the discussion:
> http://marc.info/?l=linux-mm&m=146373278424897&w=2
> 
> In my opinion, checking whether kswapd is wake up
> could be good.

This is still not enough because it doesn't help memcg loads. kswapd
might be sleeping but the memcg reclaim can still be active. So I think
we really need to do ~__GFP_DIRECT_RECLAIM thing.

> It's up to you. I can take an action according to community's decision.

IMHO we should drop the current ALLOCSTALL heuristic and replace it with
~__GFP_DIRECT_RECLAIM.
-- 
Michal Hocko
SUSE Labs