Re: [PATCH] Memory hot added,The memory can not been added to movable zone

[Vlastimil Babka]

On 08/25/2015 12:25 PM, Changsheng Liu wrote:
> Thanks very much for your review, I can move the memory from normal zone
> to movable zone succesfully.
> And thank you for let me understand the memory mechanism better.
> å 2015/8/25 3:15, Yasuaki Ishimatsu åé:

So you agree to drop the patch from -mm?

> > Hi
> > On Thu, 20 Aug 2015 14:15:13 +0800
> > Changsheng Liu <liuchangsheng@xxxxxxxxxx> wrote:
> >
> > > Hi Andrew Morton:
> > > First, thanks very much for your review, I will update codes according
> > > to  your suggestio
> > >
> > > å 2015/8/20 7:50, Andrew Morton åé:
> > > > On Wed, 19 Aug 2015 04:18:26 -0400 Changsheng Liu <liuchangsheng@xxxxxxxxxx> wrote:
> > > >
> > > > > From: Changsheng Liu <liuchangcheng@xxxxxxxxxx>
> > > > >
> > > > > When memory hot added, the function should_add_memory_movable
> > > > > always return 0,because the movable zone is empty,
> > > > > so the memory that hot added will add to normal zone even if
> > > > > we want to remove the memory.
> > > > > So we change the function should_add_memory_movable,if the user
> > > > > config CONFIG_MOVABLE_NODE it will return 1 when
> > > > > movable zone is empty
> > > > I cleaned this up a bit:
> > > >
> > > > : Subject: mm: memory hot-add: memory can not been added to movable zone
> > > > :
> > > > : When memory is hot added, should_add_memory_movable() always returns 0
> > > > : because the movable zone is empty, so the memory that was hot added will
> > > > : add to the normal zone even if we want to remove the memory.
> > > > :
> > > > : So we change should_add_memory_movable(): if the user config
> > > > : CONFIG_MOVABLE_NODE it will return 1 when the movable zone is empty.
> > > >
> > > > But I don't understand the "even if we want to remove the memory".
> > > > This is hot-add, not hot-remove.  What do you mean here?
> > >        After the system startup, we hot added one memory. After some time
> > > we wanted to hot remove the memroy that was hot added,
> > >        but we could not offline some memory blocks successfully because
> > > the memory was added to normal zone defaultly and the value of the file
> > >        named removable under some memory blocks is 0.
> > For this, we prepared online_movable. When memory is onlined by online_movable,
> > the memory move from ZONE_NORMAL to ZONE_MOVABLE.
> >
> > Ex.
> > # echo online_movable > /sys/devices/system/memory/memoryXXX/state
> >
> > Thanks,
> > Yasuaki Ishimatsu
> >
> > >        we checked the value of the file under some memory blocks as follows:
> > >        "cat /sys/devices/system/memory/ memory***/removable"
> > >        When memory being hot added we let the memory be added to movable
> > > zone,
> > >        so we will be able to hot remove the memory that have been hot added
> > > > > --- a/mm/memory_hotplug.c
> > > > > +++ b/mm/memory_hotplug.c
> > > > > @@ -1198,9 +1198,13 @@ static int should_add_memory_movable(int nid, u64 start, u64 size)
> > > > >     	pg_data_t *pgdat = NODE_DATA(nid);
> > > > >     	struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
> > > > >
> > > > > -	if (zone_is_empty(movable_zone))
> > > > > +	if (zone_is_empty(movable_zone)) {
> > > > > +	#ifdef CONFIG_MOVABLE_NODE
> > > > > +		return 1;
> > > > > +	#else
> > > > >     		return 0;
> > > > > -
> > > > > +	#endif
> > > > > +	}
> > > > >     	if (movable_zone->zone_start_pfn <= start_pfn)
> > > > >     		return 1;
> > > > Cleaner:
> > > >
> > > > --- a/mm/memory_hotplug.c~memory-hot-addedthe-memory-can-not-been-added-to-movable-zone-fix
> > > > +++ a/mm/memory_hotplug.c
> > > > @@ -1181,13 +1181,9 @@ static int should_add_memory_movable(int
> > > >     	pg_data_t *pgdat = NODE_DATA(nid);
> > > >     	struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
> > > >
> > > > -	if (zone_is_empty(movable_zone)) {
> > > > -	#ifdef CONFIG_MOVABLE_NODE
> > > > -		return 1;
> > > > -	#else
> > > > -		return 0;
> > > > -	#endif
> > > > -	}
> > > > +	if (zone_is_empty(movable_zone))
> > > > +		return IS_ENABLED(CONFIG_MOVABLE_NODE);
> > > > +
> > > >     	if (movable_zone->zone_start_pfn <= start_pfn)
> > > >     		return 1;
> > > >
> > > > _
> > > >
> > > > .
> > .

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