linux-kernel - RE: [RFC] MADV_FREE doesn't work when doesn't have swap partition

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Message-ID: <35FD53F367049845BC99AC72306C23D103EDAF89E152@CNBJMBX05.corpusers.net>
Date:	Fri, 19 Dec 2014 14:54:48 +0800
From:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
To:	'Minchan Kim' <minchan@...nel.org>
CC:	'Konstantin Khlebnikov' <koct9i@...il.com>,
	"'Kirill A. Shutemov'" <kirill@...temov.name>,
	'Andrew Morton' <akpm@...ux-foundation.org>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	"'linux-mm@...ck.org'" <linux-mm@...ck.org>,
	"'linux-arm-kernel@...ts.infradead.org'" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'n-horiguchi@...jp.nec.com'" <n-horiguchi@...jp.nec.com>
Subject: RE: [RFC] MADV_FREE doesn't work when doesn't have swap partition

> -----Original Message-----
> From: Minchan Kim [mailto:minchan@...nel.org]
> Sent: Friday, December 19, 2014 9:05 AM
> To: Wang, Yalin
> Cc: 'Konstantin Khlebnikov'; 'Kirill A. Shutemov'; 'Andrew Morton'; 'linux-
> kernel@...r.kernel.org'; 'linux-mm@...ck.org'; 'linux-arm-
> kernel@...ts.infradead.org'; 'n-horiguchi@...jp.nec.com'
> Subject: Re: [RFC] MADV_FREE doesn't work when doesn't have swap partition
> 
> On Thu, Dec 18, 2014 at 11:50:01AM +0800, Wang, Yalin wrote:
> > I notice this commit:
> > mm: support madvise(MADV_FREE),
> >
> > it can free clean anonymous pages directly, doesn't need pageout to
> > swap partition,
> >
> > but I found it doesn't work on my platform, which don't enable any
> > swap partitions.
> 
> Current implementation, if there is no empty slot in swap, it does instant
> free instead of delayed free. Look at madvise_vma.
> 
> >
> > I make a change for this.
> > Just to explain my issue clearly,
> > Do we need some other checks to still scan anonymous pages even Don't
> > have swap partition but have clean anonymous pages?
> 
> There is a few places we should consider if you want to scan anonymous page
> withotu swap. Refer 69c854817566 and 74e3f3c3391d.
> 
> However, it's not simple at the moment. If we reenable anonymous scan
> without swap, it would make much regress of reclaim. So my direction is
> move normal anonymos pages into unevictable LRU list because they're real
> unevictable without swap and put delayed freeing pages into anon LRU list
> and age them.
> 
I understand your solution, sounds a great idea!
When this design will be merged into main stream?

Thanks.