Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Yasuaki Ishimatsu]

On Wed, 21 Oct 2015 17:18:36 +0800
Tang Chen  wrote:

> 
> On 10/21/2015 05:00 PM, Vlastimil Babka wrote:
> > On 10/21/2015 04:20 AM, Changsheng Liu wrote:
> >>
> >>
> >> 在 2015/10/15 0:18, Vlastimil Babka 写道:
> >>> On 10/12/2015 08:58 AM, Changsheng Liu wrote:
>  From: Changsheng Liu 
> 
>  After the user config CONFIG_MOVABLE_NODE,
>  When the memory is hot added, should_add_memory_movable() return 0
>  because all zones including ZONE_MOVABLE are empty,
>  so the memory that was hot added will be assigned to ZONE_NORMAL
>  and ZONE_NORMAL will be created firstly.
>  But we want the whole node to be added to ZONE_MOVABLE by default.
> 
>  So we change should_add_memory_movable(): if the user config
>  CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
>  and the ZONE_NORMAL is empty or the pfn of the hot-added memory
>  is after the end of the ZONE_NORMAL it will always return 1
>  and then the whole node will be added to ZONE_MOVABLE by default.
>  If we want the node to be assigned to ZONE_NORMAL,
>  we can do it as follows:
>  "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> 
>  By the patch, the behavious of kernel is changed by sysctl,
>  user can automatically create movable memory
>  by only the following udev rule:
>  SUBSYSTEM=="memory", ACTION=="add",
>  ATTR{state}=="offline", ATTR{state}="online"
> >>   I'm sorry for replying you so late due to the busy business trip.
> >>> So just to be clear, we are adding a new sysctl, because the existing
> >>> movable_node kernel option, which is checked by 
> >>> movable_node_is_enabled(), and
> >>> does the same thing for non-hot-added-memory (?) cannot be reused 
> >>> for hot-added
> >>> memory, as that would be a potentially surprising behavior change? 
> >>> Correct? Then
> >>> this should be mentioned in the changelog too, and wherever 
> >>> "movable_node" is
> >>> documented should also mention the new sysctl. Personally, I would 
> >>> expect
> >>> movable_node to affect hot-added memory as well, and would be 
> >>> surprised that it
> >>> doesn't...
> >>   I think it can let the user decides when to use this feature.
> >>   The user can enable the feature when making the hot_added memory
> >> of a node movable and
> >>   make the feature disable to assign the hot_added memory of the 
> >> next
> >> node to ZONE_NORMAL .
> >
> > So you mean sysctl is more flexible than boot option. OK, but wasn't 
> > such flexibility already provided by "echo online_kernel" vs "echo 
> > online_movable"? It doesn't sound like a strong reason for a new 
> > sysctl? Not doing surprising behavior change maybe does...
> > .
> >
> Hi Vlastimil,
> 
> The current kernel will add hot-added memory to ZONE_NORMAL by default. 
> If users use a udev rule as below:
> 
> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
> ATTR{state}="online"
> 
> it will online the memory as normal memory, which will not be hotpluggable.
> 
> Please refer to: https://lkml.org/lkml/2015/10/9/58
> 
> I think this is the root motivation of the patch.
> 

> But BTW, I'm quite familiar with udev rules, but can something like this 
> work ?
> 
> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
> ATTR{state}="online_movable"
> 
> I'm not sure. I added Ishimatu in.

I think the udev rules fails to online memory as movable.

When hot adding memory, the memory is managed as ZONE_NORMAL.
And add events of memory section are notified to udev in ascending
order, like 0->1->2->3. Thus udev starts to online memory from section 0.
But to change zone from ZONE_NORMAL to ZONE_MOVALBE, udev onlines memory
in descending order, like 3->2->1->0. So the udev rules cannot online
memory as movable.

Thanks,
Yasuaki Ishimatsu

> 
> For now, I think, if the above rule works, we don't need this patch. If 
> not, maybe we should just change the kernel behavior to make the 
> hot-added memory be added to ZONE_MOVABLE by default.
> 
> I don't have objection. But a sysctl doesn't sound necessary.



> 
> Thanks.
> 
--
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Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Yasuaki Ishimatsu]

On Wed, 21 Oct 2015 17:18:36 +0800
Tang Chen  wrote:

> 
> On 10/21/2015 05:00 PM, Vlastimil Babka wrote:
> > On 10/21/2015 04:20 AM, Changsheng Liu wrote:
> >>
> >>
> >> 在 2015/10/15 0:18, Vlastimil Babka 写道:
> >>> On 10/12/2015 08:58 AM, Changsheng Liu wrote:
>  From: Changsheng Liu 
> 
>  After the user config CONFIG_MOVABLE_NODE,
>  When the memory is hot added, should_add_memory_movable() return 0
>  because all zones including ZONE_MOVABLE are empty,
>  so the memory that was hot added will be assigned to ZONE_NORMAL
>  and ZONE_NORMAL will be created firstly.
>  But we want the whole node to be added to ZONE_MOVABLE by default.
> 
>  So we change should_add_memory_movable(): if the user config
>  CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
>  and the ZONE_NORMAL is empty or the pfn of the hot-added memory
>  is after the end of the ZONE_NORMAL it will always return 1
>  and then the whole node will be added to ZONE_MOVABLE by default.
>  If we want the node to be assigned to ZONE_NORMAL,
>  we can do it as follows:
>  "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> 
>  By the patch, the behavious of kernel is changed by sysctl,
>  user can automatically create movable memory
>  by only the following udev rule:
>  SUBSYSTEM=="memory", ACTION=="add",
>  ATTR{state}=="offline", ATTR{state}="online"
> >>   I'm sorry for replying you so late due to the busy business trip.
> >>> So just to be clear, we are adding a new sysctl, because the existing
> >>> movable_node kernel option, which is checked by 
> >>> movable_node_is_enabled(), and
> >>> does the same thing for non-hot-added-memory (?) cannot be reused 
> >>> for hot-added
> >>> memory, as that would be a potentially surprising behavior change? 
> >>> Correct? Then
> >>> this should be mentioned in the changelog too, and wherever 
> >>> "movable_node" is
> >>> documented should also mention the new sysctl. Personally, I would 
> >>> expect
> >>> movable_node to affect hot-added memory as well, and would be 
> >>> surprised that it
> >>> doesn't...
> >>   I think it can let the user decides when to use this feature.
> >>   The user can enable the feature when making the hot_added memory
> >> of a node movable and
> >>   make the feature disable to assign the hot_added memory of the 
> >> next
> >> node to ZONE_NORMAL .
> >
> > So you mean sysctl is more flexible than boot option. OK, but wasn't 
> > such flexibility already provided by "echo online_kernel" vs "echo 
> > online_movable"? It doesn't sound like a strong reason for a new 
> > sysctl? Not doing surprising behavior change maybe does...
> > .
> >
> Hi Vlastimil,
> 
> The current kernel will add hot-added memory to ZONE_NORMAL by default. 
> If users use a udev rule as below:
> 
> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
> ATTR{state}="online"
> 
> it will online the memory as normal memory, which will not be hotpluggable.
> 
> Please refer to: https://lkml.org/lkml/2015/10/9/58
> 
> I think this is the root motivation of the patch.
> 

> But BTW, I'm quite familiar with udev rules, but can something like this 
> work ?
> 
> SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
> ATTR{state}="online_movable"
> 
> I'm not sure. I added Ishimatu in.

I think the udev rules fails to online memory as movable.

When hot adding memory, the memory is managed as ZONE_NORMAL.
And add events of memory section are notified to udev in ascending
order, like 0->1->2->3. Thus udev starts to online memory from section 0.
But to change zone from ZONE_NORMAL to ZONE_MOVALBE, udev onlines memory
in descending order, like 3->2->1->0. So the udev rules cannot online
memory as movable.

Thanks,
Yasuaki Ishimatsu

> 
> For now, I think, if the above rule works, we don't need this patch. If 
> not, maybe we should just change the kernel behavior to make the 
> hot-added memory be added to ZONE_MOVABLE by default.
> 
> I don't have objection. But a sysctl doesn't sound necessary.



> 
> Thanks.
> 
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Tang Chen]

On 10/21/2015 05:18 PM, Tang Chen wrote:


On 10/21/2015 05:00 PM, Vlastimil Babka wrote:

On 10/21/2015 04:20 AM, Changsheng Liu wrote:



在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable 
is 1

and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

  I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by 
movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused 
for hot-added
memory, as that would be a potentially surprising behavior change? 
Correct? Then
this should be mentioned in the changelog too, and wherever 
"movable_node" is
documented should also mention the new sysctl. Personally, I would 
expect
movable_node to affect hot-added memory as well, and would be 
surprised that it

doesn't...

  I think it can let the user decides when to use this feature.
  The user can enable the feature when making the hot_added memory
of a node movable and
  make the feature disable to assign the hot_added memory of the 
next

node to ZONE_NORMAL .


So you mean sysctl is more flexible than boot option. OK, but wasn't 
such flexibility already provided by "echo online_kernel" vs "echo 
online_movable"? It doesn't sound like a strong reason for a new 
sysctl? Not doing surprising behavior change maybe does...

.


Hi Vlastimil,

The current kernel will add hot-added memory to ZONE_NORMAL by 
default. If users use a udev rule as below:


SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
ATTR{state}="online"


it will online the memory as normal memory, which will not be 
hotpluggable.


Please refer to: https://lkml.org/lkml/2015/10/9/58

I think this is the root motivation of the patch.

But BTW, I'm quite familiar with udev rules, but can something like 
this work ?


sorry, I'm NOT quite familiar with udev rules, ..



SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
ATTR{state}="online_movable"


I'm not sure. I added Ishimatu in.

For now, I think, if the above rule works, we don't need this patch. 
If not, maybe we should just change the kernel behavior to make the 
hot-added memory be added to ZONE_MOVABLE by default.


I don't have objection. But a sysctl doesn't sound necessary.

Thanks.

--
To unsubscribe from this list: send the line "unsubscribe 
linux-kernel" in

the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
.



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Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Tang Chen]

On 10/21/2015 05:00 PM, Vlastimil Babka wrote:

On 10/21/2015 04:20 AM, Changsheng Liu wrote:



在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

  I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by 
movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused 
for hot-added
memory, as that would be a potentially surprising behavior change? 
Correct? Then
this should be mentioned in the changelog too, and wherever 
"movable_node" is
documented should also mention the new sysctl. Personally, I would 
expect
movable_node to affect hot-added memory as well, and would be 
surprised that it

doesn't...

  I think it can let the user decides when to use this feature.
  The user can enable the feature when making the hot_added memory
of a node movable and
  make the feature disable to assign the hot_added memory of the 
next

node to ZONE_NORMAL .


So you mean sysctl is more flexible than boot option. OK, but wasn't 
such flexibility already provided by "echo online_kernel" vs "echo 
online_movable"? It doesn't sound like a strong reason for a new 
sysctl? Not doing surprising behavior change maybe does...

.


Hi Vlastimil,

The current kernel will add hot-added memory to ZONE_NORMAL by default. 
If users use a udev rule as below:


SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"

it will online the memory as normal memory, which will not be hotpluggable.

Please refer to: https://lkml.org/lkml/2015/10/9/58

I think this is the root motivation of the patch.

But BTW, I'm quite familiar with udev rules, but can something like this 
work ?


SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
ATTR{state}="online_movable"

I'm not sure. I added Ishimatu in.

For now, I think, if the above rule works, we don't need this patch. If 
not, maybe we should just change the kernel behavior to make the 
hot-added memory be added to ZONE_MOVABLE by default.


I don't have objection. But a sysctl doesn't sound necessary.

Thanks.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Vlastimil Babka]

On 10/21/2015 04:20 AM, Changsheng Liu wrote:



在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

  I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...

  I think it can let the user decides when to use this feature.
  The user can enable the feature when making the hot_added memory
of a node movable and
  make the feature disable to assign the hot_added memory of the next
node to ZONE_NORMAL .


So you mean sysctl is more flexible than boot option. OK, but wasn't 
such flexibility already provided by "echo online_kernel" vs "echo 
online_movable"? It doesn't sound like a strong reason for a new sysctl? 
Not doing surprising behavior change maybe does...

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Tang Chen]

On 10/21/2015 05:00 PM, Vlastimil Babka wrote:

On 10/21/2015 04:20 AM, Changsheng Liu wrote:



在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

  I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by 
movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused 
for hot-added
memory, as that would be a potentially surprising behavior change? 
Correct? Then
this should be mentioned in the changelog too, and wherever 
"movable_node" is
documented should also mention the new sysctl. Personally, I would 
expect
movable_node to affect hot-added memory as well, and would be 
surprised that it

doesn't...

  I think it can let the user decides when to use this feature.
  The user can enable the feature when making the hot_added memory
of a node movable and
  make the feature disable to assign the hot_added memory of the 
next

node to ZONE_NORMAL .


So you mean sysctl is more flexible than boot option. OK, but wasn't 
such flexibility already provided by "echo online_kernel" vs "echo 
online_movable"? It doesn't sound like a strong reason for a new 
sysctl? Not doing surprising behavior change maybe does...

.


Hi Vlastimil,

The current kernel will add hot-added memory to ZONE_NORMAL by default. 
If users use a udev rule as below:


SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"

it will online the memory as normal memory, which will not be hotpluggable.

Please refer to: https://lkml.org/lkml/2015/10/9/58

I think this is the root motivation of the patch.

But BTW, I'm quite familiar with udev rules, but can something like this 
work ?


SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
ATTR{state}="online_movable"

I'm not sure. I added Ishimatu in.

For now, I think, if the above rule works, we don't need this patch. If 
not, maybe we should just change the kernel behavior to make the 
hot-added memory be added to ZONE_MOVABLE by default.


I don't have objection. But a sysctl doesn't sound necessary.

Thanks.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Tang Chen]

On 10/21/2015 05:18 PM, Tang Chen wrote:


On 10/21/2015 05:00 PM, Vlastimil Babka wrote:

On 10/21/2015 04:20 AM, Changsheng Liu wrote:



在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable 
is 1

and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

  I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by 
movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused 
for hot-added
memory, as that would be a potentially surprising behavior change? 
Correct? Then
this should be mentioned in the changelog too, and wherever 
"movable_node" is
documented should also mention the new sysctl. Personally, I would 
expect
movable_node to affect hot-added memory as well, and would be 
surprised that it

doesn't...

  I think it can let the user decides when to use this feature.
  The user can enable the feature when making the hot_added memory
of a node movable and
  make the feature disable to assign the hot_added memory of the 
next

node to ZONE_NORMAL .


So you mean sysctl is more flexible than boot option. OK, but wasn't 
such flexibility already provided by "echo online_kernel" vs "echo 
online_movable"? It doesn't sound like a strong reason for a new 
sysctl? Not doing surprising behavior change maybe does...

.


Hi Vlastimil,

The current kernel will add hot-added memory to ZONE_NORMAL by 
default. If users use a udev rule as below:


SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
ATTR{state}="online"


it will online the memory as normal memory, which will not be 
hotpluggable.


Please refer to: https://lkml.org/lkml/2015/10/9/58

I think this is the root motivation of the patch.

But BTW, I'm quite familiar with udev rules, but can something like 
this work ?


sorry, I'm NOT quite familiar with udev rules, ..



SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", 
ATTR{state}="online_movable"


I'm not sure. I added Ishimatu in.

For now, I think, if the above rule works, we don't need this patch. 
If not, maybe we should just change the kernel behavior to make the 
hot-added memory be added to ZONE_MOVABLE by default.


I don't have objection. But a sysctl doesn't sound necessary.

Thanks.

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Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Vlastimil Babka]

On 10/21/2015 04:20 AM, Changsheng Liu wrote:



在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

  I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...

  I think it can let the user decides when to use this feature.
  The user can enable the feature when making the hot_added memory
of a node movable and
  make the feature disable to assign the hot_added memory of the next
node to ZONE_NORMAL .


So you mean sysctl is more flexible than boot option. OK, but wasn't 
such flexibility already provided by "echo online_kernel" vs "echo 
online_movable"? It doesn't sound like a strong reason for a new sysctl? 
Not doing surprising behavior change maybe does...

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Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Changsheng Liu]

在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...

I think it can let the user decides when to use this feature.
The user can enable the feature when making the hot_added memory  
of a node movable and
make the feature disable to assign the hot_added memory of the next 
node to ZONE_NORMAL .



Signed-off-by: Changsheng Liu 
Signed-off-by: Xiaofeng Yan 
Tested-by: Dongdong Fan 
Cc: Wang Nan 
Cc: Dave Hansen 
Cc: Yinghai Lu 
Cc: Tang Chen 
Cc: Yasuaki Ishimatsu 
Cc: Toshi Kani 
Cc: Xishi Qiu 
---
  Documentation/memory-hotplug.txt |5 -
  kernel/sysctl.c  |   15 +++
  mm/memory_hotplug.c  |   24 
  3 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index ce2cfcf..7ac7485 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -277,7 +277,7 @@ And if the memory block is in ZONE_MOVABLE, you can change 
it to ZONE_NORMAL:
  After this, memory block XXX's state will be 'online' and the amount of
  available memory will be increased.
  
-Currently, newly added memory is added as ZONE_NORMAL (for powerpc, ZONE_DMA).

+Currently, newly added memory is added as ZONE_NORMAL or ZONE_MOVABLE (for 
powerpc, ZONE_DMA).
  This may be changed in future.
  
  
@@ -319,6 +319,9 @@ creates ZONE_MOVABLE as following.

Size of memory not for movable pages (not for offline) is TOTAL - .
Size of memory for movable pages (for offline) is .
  
+And a sysctl parameter for assigning the hot added memory to ZONE_MOVABLE is

+supported. If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
+memory will be assigned to ZONE_MOVABLE by default.
  
  Note: Unfortunately, there is no information to show which memory block belongs

  to ZONE_MOVABLE. This is TBD.
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 19b62b5..16b1501 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -166,6 +166,10 @@ extern int unaligned_dump_stack;
  extern int no_unaligned_warning;
  #endif
  
+#ifdef CONFIG_MOVABLE_NODE

+extern int hotadd_memory_as_movable;
+#endif
+
  #ifdef CONFIG_PROC_SYSCTL
  
  #define SYSCTL_WRITES_LEGACY	-1

@@ -1139,6 +1143,17 @@ static struct ctl_table kern_table[] = {
.proc_handler   = timer_migration_handler,
},
  #endif
+/*If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
+ * memory will be assigned to ZONE_MOVABLE by default.*/
+#ifdef CONFIG_MOVABLE_NODE
+   {
+   .procname   = "hotadd_memory_as_movable",
+   .data   = _memory_as_movable,
+   .maxlen = sizeof(int),
+   .mode   = 0644,
+   .proc_handler   = proc_dointvec,
+   },
+#endif
{ }
  };
  
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c

index 26fbba7..eca5512 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -37,6 +37,11 @@
  
  #include "internal.h"
  
+/*If the global variable value is 1,

+ * the hot added memory will be assigned to ZONE_MOVABLE by default
+ */
+int hotadd_memory_as_movable;
+
  /*
   * online_page_callback contains pointer to current page onlining function.
   * Initially it is 

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Changsheng Liu]

在 2015/10/15 0:18, Vlastimil Babka 写道:

On 10/12/2015 08:58 AM, Changsheng Liu wrote:

From: Changsheng Liu 

After the user config CONFIG_MOVABLE_NODE,
When the memory is hot added, should_add_memory_movable() return 0
because all zones including ZONE_MOVABLE are empty,
so the memory that was hot added will be assigned to ZONE_NORMAL
and ZONE_NORMAL will be created firstly.
But we want the whole node to be added to ZONE_MOVABLE by default.

So we change should_add_memory_movable(): if the user config
CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
and the ZONE_NORMAL is empty or the pfn of the hot-added memory
is after the end of the ZONE_NORMAL it will always return 1
and then the whole node will be added to ZONE_MOVABLE by default.
If we want the node to be assigned to ZONE_NORMAL,
we can do it as follows:
"echo online_kernel > /sys/devices/system/memory/memoryXXX/state"

By the patch, the behavious of kernel is changed by sysctl,
user can automatically create movable memory
by only the following udev rule:
SUBSYSTEM=="memory", ACTION=="add",
ATTR{state}=="offline", ATTR{state}="online"

I'm sorry for replying you so late due to the busy business trip.

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...

I think it can let the user decides when to use this feature.
The user can enable the feature when making the hot_added memory  
of a node movable and
make the feature disable to assign the hot_added memory of the next 
node to ZONE_NORMAL .



Signed-off-by: Changsheng Liu 
Signed-off-by: Xiaofeng Yan 
Tested-by: Dongdong Fan 
Cc: Wang Nan 
Cc: Dave Hansen 
Cc: Yinghai Lu 
Cc: Tang Chen 
Cc: Yasuaki Ishimatsu 
Cc: Toshi Kani 
Cc: Xishi Qiu 
---
  Documentation/memory-hotplug.txt |5 -
  kernel/sysctl.c  |   15 +++
  mm/memory_hotplug.c  |   24 
  3 files changed, 43 insertions(+), 1 deletions(-)

diff --git a/Documentation/memory-hotplug.txt b/Documentation/memory-hotplug.txt
index ce2cfcf..7ac7485 100644
--- a/Documentation/memory-hotplug.txt
+++ b/Documentation/memory-hotplug.txt
@@ -277,7 +277,7 @@ And if the memory block is in ZONE_MOVABLE, you can change 
it to ZONE_NORMAL:
  After this, memory block XXX's state will be 'online' and the amount of
  available memory will be increased.
  
-Currently, newly added memory is added as ZONE_NORMAL (for powerpc, ZONE_DMA).

+Currently, newly added memory is added as ZONE_NORMAL or ZONE_MOVABLE (for 
powerpc, ZONE_DMA).
  This may be changed in future.
  
  
@@ -319,6 +319,9 @@ creates ZONE_MOVABLE as following.

Size of memory not for movable pages (not for offline) is TOTAL - .
Size of memory for movable pages (for offline) is .
  
+And a sysctl parameter for assigning the hot added memory to ZONE_MOVABLE is

+supported. If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
+memory will be assigned to ZONE_MOVABLE by default.
  
  Note: Unfortunately, there is no information to show which memory block belongs

  to ZONE_MOVABLE. This is TBD.
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 19b62b5..16b1501 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -166,6 +166,10 @@ extern int unaligned_dump_stack;
  extern int no_unaligned_warning;
  #endif
  
+#ifdef CONFIG_MOVABLE_NODE

+extern int hotadd_memory_as_movable;
+#endif
+
  #ifdef CONFIG_PROC_SYSCTL
  
  #define SYSCTL_WRITES_LEGACY	-1

@@ -1139,6 +1143,17 @@ static struct ctl_table kern_table[] = {
.proc_handler   = timer_migration_handler,
},
  #endif
+/*If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
+ * memory will be assigned to ZONE_MOVABLE by default.*/
+#ifdef CONFIG_MOVABLE_NODE
+   {
+   .procname   = "hotadd_memory_as_movable",
+   .data   = _memory_as_movable,
+   .maxlen = sizeof(int),
+   .mode   = 0644,
+   .proc_handler   = proc_dointvec,
+   },
+#endif
{ }
  };
  
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c

index 26fbba7..eca5512 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -37,6 +37,11 @@
  
  #include "internal.h"

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Vlastimil Babka]

On 10/12/2015 08:58 AM, Changsheng Liu wrote:
> From: Changsheng Liu 
> 
> After the user config CONFIG_MOVABLE_NODE,
> When the memory is hot added, should_add_memory_movable() return 0
> because all zones including ZONE_MOVABLE are empty,
> so the memory that was hot added will be assigned to ZONE_NORMAL
> and ZONE_NORMAL will be created firstly.
> But we want the whole node to be added to ZONE_MOVABLE by default.
> 
> So we change should_add_memory_movable(): if the user config
> CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
> and the ZONE_NORMAL is empty or the pfn of the hot-added memory
> is after the end of the ZONE_NORMAL it will always return 1
> and then the whole node will be added to ZONE_MOVABLE by default.
> If we want the node to be assigned to ZONE_NORMAL,
> we can do it as follows:
> "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> 
> By the patch, the behavious of kernel is changed by sysctl,
> user can automatically create movable memory
> by only the following udev rule:
> SUBSYSTEM=="memory", ACTION=="add",
> ATTR{state}=="offline", ATTR{state}="online"

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...

> Signed-off-by: Changsheng Liu 
> Signed-off-by: Xiaofeng Yan 
> Tested-by: Dongdong Fan 
> Cc: Wang Nan 
> Cc: Dave Hansen 
> Cc: Yinghai Lu 
> Cc: Tang Chen 
> Cc: Yasuaki Ishimatsu 
> Cc: Toshi Kani 
> Cc: Xishi Qiu 
> ---
>  Documentation/memory-hotplug.txt |5 -
>  kernel/sysctl.c  |   15 +++
>  mm/memory_hotplug.c  |   24 
>  3 files changed, 43 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/memory-hotplug.txt 
> b/Documentation/memory-hotplug.txt
> index ce2cfcf..7ac7485 100644
> --- a/Documentation/memory-hotplug.txt
> +++ b/Documentation/memory-hotplug.txt
> @@ -277,7 +277,7 @@ And if the memory block is in ZONE_MOVABLE, you can 
> change it to ZONE_NORMAL:
>  After this, memory block XXX's state will be 'online' and the amount of
>  available memory will be increased.
>  
> -Currently, newly added memory is added as ZONE_NORMAL (for powerpc, 
> ZONE_DMA).
> +Currently, newly added memory is added as ZONE_NORMAL or ZONE_MOVABLE (for 
> powerpc, ZONE_DMA).
>  This may be changed in future.
>  
>  
> @@ -319,6 +319,9 @@ creates ZONE_MOVABLE as following.
>Size of memory not for movable pages (not for offline) is TOTAL - .
>Size of memory for movable pages (for offline) is .
>  
> +And a sysctl parameter for assigning the hot added memory to ZONE_MOVABLE is
> +supported. If the value of "kernel/hotadd_memory_as_movable" is 1,the hot 
> added
> +memory will be assigned to ZONE_MOVABLE by default.
>  
>  Note: Unfortunately, there is no information to show which memory block 
> belongs
>  to ZONE_MOVABLE. This is TBD.
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 19b62b5..16b1501 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -166,6 +166,10 @@ extern int unaligned_dump_stack;
>  extern int no_unaligned_warning;
>  #endif
>  
> +#ifdef CONFIG_MOVABLE_NODE
> +extern int hotadd_memory_as_movable;
> +#endif
> +
>  #ifdef CONFIG_PROC_SYSCTL
>  
>  #define SYSCTL_WRITES_LEGACY -1
> @@ -1139,6 +1143,17 @@ static struct ctl_table kern_table[] = {
>   .proc_handler   = timer_migration_handler,
>   },
>  #endif
> +/*If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
> + * memory will be assigned to ZONE_MOVABLE by default.*/
> +#ifdef CONFIG_MOVABLE_NODE
> + {
> + .procname   = "hotadd_memory_as_movable",
> + .data   = _memory_as_movable,
> + .maxlen = sizeof(int),
> + .mode   = 0644,
> + .proc_handler   = proc_dointvec,
> + },
> +#endif
>   { }
>  };
>  
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 26fbba7..eca5512 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -37,6 +37,11 @@
>  
>  #include "internal.h"
>  
> +/*If the global variable value is 1,
> + * the hot added memory will be assigned to ZONE_MOVABLE by default
> + */
> +int hotadd_memory_as_movable;
> +
>  /*
>   * online_page_callback contains pointer to current page onlining function.
>   * Initially it is generic_online_page(). If it is required it could be
> @@ -1190,6 +1195,9 @@ static int check_hotplug_memory_range(u64 start, u64 
> size)
>  /*
>   * If movable zone has already been setup, 

Re: [PATCH V7] mm: memory hot-add: memory can not be added to movable zone defaultly

[Vlastimil Babka]

On 10/12/2015 08:58 AM, Changsheng Liu wrote:
> From: Changsheng Liu 
> 
> After the user config CONFIG_MOVABLE_NODE,
> When the memory is hot added, should_add_memory_movable() return 0
> because all zones including ZONE_MOVABLE are empty,
> so the memory that was hot added will be assigned to ZONE_NORMAL
> and ZONE_NORMAL will be created firstly.
> But we want the whole node to be added to ZONE_MOVABLE by default.
> 
> So we change should_add_memory_movable(): if the user config
> CONFIG_MOVABLE_NODE and sysctl parameter hotadd_memory_as_movable is 1
> and the ZONE_NORMAL is empty or the pfn of the hot-added memory
> is after the end of the ZONE_NORMAL it will always return 1
> and then the whole node will be added to ZONE_MOVABLE by default.
> If we want the node to be assigned to ZONE_NORMAL,
> we can do it as follows:
> "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> 
> By the patch, the behavious of kernel is changed by sysctl,
> user can automatically create movable memory
> by only the following udev rule:
> SUBSYSTEM=="memory", ACTION=="add",
> ATTR{state}=="offline", ATTR{state}="online"

So just to be clear, we are adding a new sysctl, because the existing
movable_node kernel option, which is checked by movable_node_is_enabled(), and
does the same thing for non-hot-added-memory (?) cannot be reused for hot-added
memory, as that would be a potentially surprising behavior change? Correct? Then
this should be mentioned in the changelog too, and wherever "movable_node" is
documented should also mention the new sysctl. Personally, I would expect
movable_node to affect hot-added memory as well, and would be surprised that it
doesn't...

> Signed-off-by: Changsheng Liu 
> Signed-off-by: Xiaofeng Yan 
> Tested-by: Dongdong Fan 
> Cc: Wang Nan 
> Cc: Dave Hansen 
> Cc: Yinghai Lu 
> Cc: Tang Chen 
> Cc: Yasuaki Ishimatsu 
> Cc: Toshi Kani 
> Cc: Xishi Qiu 
> ---
>  Documentation/memory-hotplug.txt |5 -
>  kernel/sysctl.c  |   15 +++
>  mm/memory_hotplug.c  |   24 
>  3 files changed, 43 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/memory-hotplug.txt 
> b/Documentation/memory-hotplug.txt
> index ce2cfcf..7ac7485 100644
> --- a/Documentation/memory-hotplug.txt
> +++ b/Documentation/memory-hotplug.txt
> @@ -277,7 +277,7 @@ And if the memory block is in ZONE_MOVABLE, you can 
> change it to ZONE_NORMAL:
>  After this, memory block XXX's state will be 'online' and the amount of
>  available memory will be increased.
>  
> -Currently, newly added memory is added as ZONE_NORMAL (for powerpc, 
> ZONE_DMA).
> +Currently, newly added memory is added as ZONE_NORMAL or ZONE_MOVABLE (for 
> powerpc, ZONE_DMA).
>  This may be changed in future.
>  
>  
> @@ -319,6 +319,9 @@ creates ZONE_MOVABLE as following.
>Size of memory not for movable pages (not for offline) is TOTAL - .
>Size of memory for movable pages (for offline) is .
>  
> +And a sysctl parameter for assigning the hot added memory to ZONE_MOVABLE is
> +supported. If the value of "kernel/hotadd_memory_as_movable" is 1,the hot 
> added
> +memory will be assigned to ZONE_MOVABLE by default.
>  
>  Note: Unfortunately, there is no information to show which memory block 
> belongs
>  to ZONE_MOVABLE. This is TBD.
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 19b62b5..16b1501 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -166,6 +166,10 @@ extern int unaligned_dump_stack;
>  extern int no_unaligned_warning;
>  #endif
>  
> +#ifdef CONFIG_MOVABLE_NODE
> +extern int hotadd_memory_as_movable;
> +#endif
> +
>  #ifdef CONFIG_PROC_SYSCTL
>  
>  #define SYSCTL_WRITES_LEGACY -1
> @@ -1139,6 +1143,17 @@ static struct ctl_table kern_table[] = {
>   .proc_handler   = timer_migration_handler,
>   },
>  #endif
> +/*If the value of "kernel/hotadd_memory_as_movable" is 1,the hot added
> + * memory will be assigned to ZONE_MOVABLE by default.*/
> +#ifdef CONFIG_MOVABLE_NODE
> + {
> + .procname   = "hotadd_memory_as_movable",
> + .data   = _memory_as_movable,
> + .maxlen = sizeof(int),
> + .mode   = 0644,
> + .proc_handler   = proc_dointvec,
> + },
> +#endif
>   { }
>  };
>  
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 26fbba7..eca5512 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -37,6 +37,11 @@
>  
>  #include "internal.h"
>  
> +/*If the global variable value is 1,
> + * the hot added memory will be assigned to ZONE_MOVABLE by default
> + */
> +int hotadd_memory_as_movable;
> +
>  /*
>   * online_page_callback contains