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

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Date:	Mon, 23 May 2016 20:29:29 +0300
From:	Ebru Akagunduz <ebru.akagunduz@...il.com>
To:	linux-mm@...ck.org
Cc:	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, mhocko@...e.cz, boaz@...xistor.com
Subject: Re: [PATCH 0/3] mm, thp: remove duplication and fix locking issues
 in swapin

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.

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

Here is the last status of the discussion:

"
Optimistic swapin collapsing

1. it could be too optimisitic to lose the gain due to evicting workingset
2. let's detect memory pressure
3. current allocstall magic is not a good idea.
4. let's change the design from optimistic to conservative
5. how we can be conservative
6. two things - detect hot pages and threshold of swap pte
7. threhsold of swap pte is already done so remained thing is detect hot page
8. how to detect hot page - let's use young bit
9. Now, we are conservatie so we will swap in when it's worth
10. let's remove allocstall magic

I think it's not off-topic.
Anyway, it's just my thought and don't have any real workload and objection.
Feel free to ignore.
"

Thanks.