Re: [PATCH V4] mm: memory hot-add: memory can not be added to movable zone defaultly

[Changsheng Liu]

On 8/31/2015 21:08, Vlastimil Babka wrote:
> On 08/31/2015 07:58 AM, Changsheng Liu wrote:
> > From: Changsheng Liu <liuchangcheng@xxxxxxxxxx>
> >
> > After the user config CONFIG_MOVABLE_NODE and movable_node kernel 
> > option,
> > When the memory is hot added, should_add_memory_movable() return 0
> > because all zones including movable zone are empty,
> > so the memory that was hot added will be added  to the normal zone
> > and the normal zone will be created firstly.
> > But we want the whole node to be added to movable zone defaultly.
> >
> > So we change should_add_memory_movable(): if the user config
> > CONFIG_MOVABLE_NODE and movable_node kernel option
> > it will always return 1 and all zones is empty at the same time,
> > so that the movable zone will be created firstly
> > and then the whole node will be added to movable zone defaultly.
> > If we want the node to be added to normal zone,
> > we can do it as follows:
> > "echo online_kernel > /sys/devices/system/memory/memoryXXX/state"
> >
> > If the memory is added to movable zone defaultly,
> > the user can offline it and add it to other zone again.
> > But if the memory is added to normal zone defaultly,
> > the user will not offline the memory used by kernel.
> >
> > Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Yasuaki Ishimatsu <yasu.isimatu@xxxxxxxxx>
> > Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> > Reviewed-by: Xiaofeng Yan <yanxiaofeng@xxxxxxxxxx>
>
> Thanks for the credit for commenting on the previous versions of the 
> patch. However, "Reviewed-by" currently means that the reviewer 
> believes the patch is OK, so you can add it only if the reviewer 
> offers it explicitly. See Documentation/SubmittingPatches section 13. 
> There was a discussion on ksummit-discuss about adding a new tag for 
> this case, but nothing was decided yet AFAIK.
   I'm sorry about it and thanks for your review,I will update the patch.
> > Signed-off-by: Changsheng Liu <liuchangcheng@xxxxxxxxxx>
> > Tested-by: Dongdong Fan <fandd@xxxxxxxxxx>
> > ---
> >   mm/memory_hotplug.c |    5 +++++
> >   1 files changed, 5 insertions(+), 0 deletions(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 26fbba7..d1149ff 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1197,6 +1197,11 @@ static int should_add_memory_movable(int nid, 
> > u64 start, u64 size)
> >       unsigned long start_pfn = start >> PAGE_SHIFT;
> >       pg_data_t *pgdat = NODE_DATA(nid);
> >       struct zone *movable_zone = pgdat->node_zones + ZONE_MOVABLE;
> > +    struct zone *normal_zone = pgdat->node_zones + ZONE_NORMAL;
> > +
> > +    if (movable_node_is_enabled()
> > +    && (zone_end_pfn(normal_zone) <= start_pfn))
> > +        return 1;
>
> I wonder if the condition is true and ZONE_NORMAL exists (but it's 
> empty?) if you intend to only add movable memory to a node, so you can 
> still hot-remove it all with this patch?
    Yes
> >       if (zone_is_empty(movable_zone))
> >           return 0;
>
> .

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