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From: Ingo Korb <ingo@akana.de>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mel@csn.ul.ie,
	cl@linux-foundation.org, yinghai@kernel.org,
	andi.kleen@intel.com, linux-kernel@vger.kernel.org
Subject: Re: PROBLEM: __offline_isolated_pages may offline too many pages
Date: Wed, 15 Dec 2010 10:25:51 +0100	[thread overview]
Message-ID: <4D08899F.4050502@akana.de> (raw)
In-Reply-To: <20101215092134.e2c8849f.kamezawa.hiroyu@jp.fujitsu.com>

On 15.12.2010 01:21, KAMEZAWA Hiroyuki wrote:

> It's designed for offline memory section>  MAX_ORDER. pageblock_nr_pages
> is tend to be smaller than that.
>
> Do you see the problem with _exsisting_ user interface of memory hotplug ?
> I think we have no control other than memory section.

The existing, exported interface (remove_memory() - the check itself is 
in offline_pages()) only checks if both start and end of the 
to-be-removed block are aligned to pageblock_nr_pages. As you noted the 
actual size and alignment requirements in __offline_isolated_pages can 
be larger that that, so I think the checks in offline_pages() should be 
changed (if 1<<MAX_ORDER is always >= pageblock_nr_pages) or extended 
(if there can be any relation between the two).

-ik

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Korb <ingo@akana.de>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mel@csn.ul.ie,
	cl@linux-foundation.org, yinghai@kernel.org,
	andi.kleen@intel.com, linux-kernel@vger.kernel.org
Subject: Re: PROBLEM: __offline_isolated_pages may offline too many pages
Date: Wed, 15 Dec 2010 10:25:51 +0100	[thread overview]
Message-ID: <4D08899F.4050502@akana.de> (raw)
In-Reply-To: <20101215092134.e2c8849f.kamezawa.hiroyu@jp.fujitsu.com>

On 15.12.2010 01:21, KAMEZAWA Hiroyuki wrote:

> It's designed for offline memory section>  MAX_ORDER. pageblock_nr_pages
> is tend to be smaller than that.
>
> Do you see the problem with _exsisting_ user interface of memory hotplug ?
> I think we have no control other than memory section.

The existing, exported interface (remove_memory() - the check itself is 
in offline_pages()) only checks if both start and end of the 
to-be-removed block are aligned to pageblock_nr_pages. As you noted the 
actual size and alignment requirements in __offline_isolated_pages can 
be larger that that, so I think the checks in offline_pages() should be 
changed (if 1<<MAX_ORDER is always >= pageblock_nr_pages) or extended 
(if there can be any relation between the two).

-ik

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  reply	other threads:[~2010-12-15  9:27 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-12-14 15:01 PROBLEM: __offline_isolated_pages may offline too many pages Ingo Korb
2010-12-14 15:01 ` Ingo Korb
2010-12-15  0:21 ` KAMEZAWA Hiroyuki
2010-12-15  0:21   ` KAMEZAWA Hiroyuki
2010-12-15  9:25   ` Ingo Korb [this message]
2010-12-15  9:25     ` Ingo Korb
2010-12-16  0:06     ` KAMEZAWA Hiroyuki
2010-12-16  0:06       ` KAMEZAWA Hiroyuki
2010-12-16 10:26       ` Mel Gorman
2010-12-16 10:26         ` Mel Gorman
2010-12-16 23:57         ` [PATCH] memory hotplug: fix alignment check (Was " KAMEZAWA Hiroyuki
2010-12-16 23:57           ` KAMEZAWA Hiroyuki

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