Subject: Re: [RFC v3 2/2] mm, compaction: make kcompactd rely on
 sysctl_extfrag_threshold
To: PINTU KUMAR <pintu_agarwal@yahoo.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
References: <1438619141-22215-2-git-send-email-vbabka@suse.cz>
 <166622926.1247366.1439140873216.JavaMail.yahoo@mail.yahoo.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Pintu Kumar <pintu.k@samsung.com>
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <55C874C9.4050803@suse.cz>
Date: Mon, 10 Aug 2015 11:54:17 +0200
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On 08/09/2015 07:21 PM, PINTU KUMAR wrote:
>>
>> -extern int fragmentation_index(struct zone *zone, unsigned int order);
>> +extern int fragmentation_index(struct zone *zone, unsigned int order,
>
>> +                            bool ignore_suitable);
>
> We would like to retain the original fragmentation_index as it is.
> Because in some cases people may be using it without kcompactd.
> In such cases, future kernel upgrades will suffer.
> In my opinion fragmentation_index should work just based on zones and order.

I don't understand the concern. If you pass 'false' to ignore_suitable, 
you get the standard behavior. Only kcompactd uses the altered behavior.

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