linux-kernel - Re: [RFC v5 0/3] mm: make swapin readahead to gain more thp performance

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Date:	Fri, 4 Mar 2016 00:08:03 +0200
From:	Ebru Akagunduz <ebru.akagunduz@...il.com>
To:	hughd@...gle.com, riel@...hat.com
Cc:	linux-mm@...ck.org, 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,
	raindel@...lanox.com
Subject: Re: [RFC v5 0/3] mm: make swapin readahead to gain more thp
 performance

On Fri, Feb 26, 2016 at 09:51:56AM -0500, Rik van Riel wrote:
> On Thu, 2016-02-25 at 22:17 -0800, Hugh Dickins wrote:
> > On Fri, 26 Feb 2016, Ebru Akagunduz wrote:
> > > in Thu, Feb 25, 2016 at 05:35:50PM -0500, Rik van Riel wrote:
> > 
> > > > Am I forgetting anything obvious?
> > > > 
> > > > Is this too aggressive?
> > > > 
> > > > Not aggressive enough?
> > > > 
> > > > Could PGPGOUT + PGSWPOUT be a useful
> > > > in-between between just PGSWPOUT or
> > > > PGSTEAL_*?
> > 
> > I've no idea offhand, would have to study what each of those
> > actually means: I'm really not familiar with them myself.
> 
> There are a few levels of page reclaim activity:
> 
> PGSTEAL_* - any page was reclaimed, this could just
>             be file pages for streaming file IO,etc
> 
> PGPGOUT   - the VM wrote pages back to disk to reclaim
>             them, this could include file pages
> 
> PGSWPOUT  - the VM wrote something to swap to reclaim
>             memory
> 
> I am not sure which level of aggressiveness khugepaged
> should check against, but my gut instinct would probably
> be the second or third.

I tested with PGPGOUT, it does not help as I expect.
As Rik's suggestion, PSWPOUT and ALLOCSTALL can be good.

I started to prepare the patch last week. Just wanted to
make you sure.

Kind regards.