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From: Vlastimil Babka <vbabka@suse.cz>
To: Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Reza Arbab <arbab@linux.vnet.ibm.com>,
	Yasuaki Ishimatsu <yasu.isimatu@gmail.com>,
	qiuxishi@huawei.com, Kani Toshimitsu <toshi.kani@hpe.com>,
	slaoub@gmail.com, Joonsoo Kim <js1304@gmail.com>,
	Daniel Kiper <daniel.kiper@oracle.com>,
	Igor Mammedov <imammedo@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wei Yang <richard.weiyang@gmail.com>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
	Michal Hocko <mhocko@suse.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	linux-api@vger.kernel.org
Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions
Date: Fri, 14 Jul 2017 14:17:55 +0200
Message-ID: <c65abd07-f024-6c66-fa55-3c23926a6ebe@suse.cz> (raw)
In-Reply-To: <20170714121233.16861-3-mhocko@kernel.org>

On 07/14/2017 02:12 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
> 
> Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has
> to precede the Movable zone in the physical memory range. The purpose of
> the movable zone is, however, not bound to any physical memory restriction.
> It merely defines a class of migrateable and reclaimable memory.
> 
> There are users (e.g. CMA) who might want to reserve specific physical
> memory ranges for their own purpose. Moreover our pfn walkers have to be
> prepared for zones overlapping in the physical range already because we
> do support interleaving NUMA nodes and therefore zones can interleave as
> well. This means we can allow each memory block to be associated with a
> different zone.
> 
> Loosen the current onlining semantic and allow explicit onlining type on
> any memblock. That means that online_{kernel,movable} will be allowed
> regardless of the physical address of the memblock as long as it is
> offline of course. This might result in moveble zone overlapping with
> other kernel zones. Default onlining then becomes a bit tricky but still
> sensible. echo online > memoryXY/state will online the given block to
> 	1) the default zone if the given range is outside of any zone
> 	2) the enclosing zone if such a zone doesn't interleave with
> 	   any other zone
>         3) the default zone if more zones interleave for this range
> where default zone is movable zone only if movable_node is enabled
> otherwise it is a kernel zone.
> 
> Here is an example of the semantic with (movable_node is not present but
> it work in an analogous way). We start with following memblocks, all of
> them offline
> memory34/valid_zones:Normal Movable
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Normal Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal Movable
> memory40/valid_zones:Normal Movable
> memory41/valid_zones:Normal Movable
> 
> Now, we online block 34 in default mode and block 37 as movable
> root@test1:/sys/devices/system/node/node1# echo online > memory34/state
> root@test1:/sys/devices/system/node/node1# echo online_movable > memory37/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal Movable
> memory40/valid_zones:Normal Movable
> memory41/valid_zones:Normal Movable
> 
> As we can see all other blocks can still be onlined both into Normal and
> Movable zones and the Normal is default because the Movable zone spans
> only block37 now.
> root@test1:/sys/devices/system/node/node1# echo online_movable > memory41/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Movable Normal
> memory39/valid_zones:Movable Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable
> 
> Now the default zone for blocks 37-41 has changed because movable zone
> spans that range.
> root@test1:/sys/devices/system/node/node1# echo online_kernel > memory39/state
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal Movable
> memory36/valid_zones:Normal Movable
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal Movable
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable Normal
> memory41/valid_zones:Movable
> 
> Note that the block 39 now belongs to the zone Normal and so block38
> falls into Normal by default as well.
> 
> For completness
> root@test1:/sys/devices/system/node/node1# for i in memory[34]?
> do
> 	echo online > $i/state 2>/dev/null
> done
> 
> memory34/valid_zones:Normal
> memory35/valid_zones:Normal
> memory36/valid_zones:Normal
> memory37/valid_zones:Movable
> memory38/valid_zones:Normal
> memory39/valid_zones:Normal
> memory40/valid_zones:Movable
> memory41/valid_zones:Movable
> 
> Implementation wise the change is quite straightforward. We can get rid
> of allow_online_pfn_range altogether. online_pages allows only offline
> nodes already. The original default_zone_for_pfn will become
> default_kernel_zone_for_pfn. New default_zone_for_pfn implements the
> above semantic. zone_for_pfn_range is slightly reorganized to implement
> kernel and movable online type explicitly and MMOP_ONLINE_KEEP becomes
> a catch all default behavior.
> 
> Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> Cc: <linux-api@vger.kernel.org>
> Signed-off-by: Michal Hocko <mhocko@suse.com>

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  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-14 12:12 [PATCH 0/2] mm, memory_hotplug: remove zone onlining restriction Michal Hocko
2017-07-14 12:12 ` [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Michal Hocko
2017-07-14 12:17   ` Vlastimil Babka [this message]
2017-07-14 14:26   ` Reza Arbab
     [not found] <20170629073509.623-1-mhocko@kernel.org>
     [not found] ` <20170629073509.623-3-mhocko@kernel.org>
2017-07-07 15:02   ` Vlastimil Babka
2017-07-10  6:45     ` Michal Hocko
2017-07-10 11:11       ` Vlastimil Babka
2017-07-10 11:17         ` Michal Hocko
2017-07-10 12:12           ` Vlastimil Babka
2017-07-10 12:30             ` Michal Hocko

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