linux-kernel - Re: [PATCH 01 of 66] disable lumpy when compaction is enabled

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Date:	Tue,  9 Nov 2010 12:18:49 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Chris Wright <chrisw@...s-sol.org>, bpicco@...hat.com,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Chris Mason <chris.mason@...cle.com>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 01 of 66] disable lumpy when compaction is enabled

> From: Andrea Arcangeli <aarcange@...hat.com>
> 
> Compaction is more reliable than lumpy, and lumpy makes the system unusable
> when it runs.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
> ---
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -274,6 +274,7 @@ unsigned long shrink_slab(unsigned long 
>  static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc,
>  				   bool sync)
>  {
> +#ifndef CONFIG_COMPACTION
>  	enum lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC;
>  
>  	/*
> @@ -294,11 +295,14 @@ static void set_lumpy_reclaim_mode(int p
>  		sc->lumpy_reclaim_mode = mode;
>  	else
>  		sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
> +#endif
>  }

I'm talking very personal thing now. I'm usually testing both feature.
Then, runtime switching makes my happy :-)
However I don't know what are you and Mel talking and agree about this.
So, If many developer prefer this approach, I don't oppose anymore.

But, I bet almost all distro choose CONFIG_COMPACTION=y. then, lumpy code
will become nearly dead code. So, I like just kill than dead code. however
it is also only my preference. ;)



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