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Date: Wed, 1 Dec 2010 11:27:32 +0100
From: Johannes Weiner <hannes@cmpxchg.org>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Rik van Riel <riel@redhat.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/7] mm: vmscan: Convert lumpy_mode into a bitmask
Message-ID: <20101201102732.GK15564@cmpxchg.org>
References: <1290440635-30071-1-git-send-email-mel@csn.ul.ie>
 <1290440635-30071-3-git-send-email-mel@csn.ul.ie>
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On Mon, Nov 22, 2010 at 03:43:50PM +0000, Mel Gorman wrote:
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -51,11 +51,20 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/vmscan.h>
>  
> -enum lumpy_mode {
> -	LUMPY_MODE_NONE,
> -	LUMPY_MODE_ASYNC,
> -	LUMPY_MODE_SYNC,
> -};
> +/*
> + * lumpy_mode determines how the inactive list is shrunk
> + * LUMPY_MODE_SINGLE: Reclaim only order-0 pages
> + * LUMPY_MODE_ASYNC:  Do not block
> + * LUMPY_MODE_SYNC:   Allow blocking e.g. call wait_on_page_writeback
> + * LUMPY_MODE_CONTIGRECLAIM: For high-order allocations, take a reference
> + *			page from the LRU and reclaim all pages within a
> + *			naturally aligned range

I find those names terribly undescriptive.  It also strikes me as an
odd set of flags.  Can't this be represented with less?

	LUMPY_MODE_ENABLED
	LUMPY_MODE_SYNC

or, after the rename,

	RECLAIM_MODE_HIGHER	= 1
	RECLAIM_MODE_SYNC	= 2
	RECLAIM_MODE_LUMPY	= 4

where compaction mode is default if RECLAIM_MODE_HIGHER, and
RECLAIM_MODE_LUMPY will go away eventually.

Also, if you have a flag name for 'reclaim with extra efforts for
higher order pages' that is better than RECLAIM_MODE_HIGHER... ;)

> +typedef unsigned __bitwise__ lumpy_mode;

lumpy_mode_t / reclaim_mode_t?