Date: Fri, 4 Mar 2016 00:08:03 +0200
From: Ebru Akagunduz <ebru.akagunduz@gmail.com>
To: hughd@google.com, riel@redhat.com
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
        kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com,
        aarcange@redhat.com, iamjoonsoo.kim@lge.com, gorcunov@openvz.org,
        linux-kernel@vger.kernel.org, mgorman@suse.de, rientjes@google.com,
        vbabka@suse.cz, aneesh.kumar@linux.vnet.ibm.com, hannes@cmpxchg.org,
        mhocko@suse.cz, boaz@plexistor.com, raindel@mellanox.com
Subject: Re: [RFC v5 0/3] mm: make swapin readahead to gain more thp
 performance
Message-ID: <20160303220803.GA9898@debian>
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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.