Hi Xishi,
On 03/05/2015 05:39 PM, Xishi Qiu wrote:
> On 2015/3/5 16:26, Gu Zheng wrote:
>
>> Hi Xishi,
>> Could you please try the following one?
>> It postpones the reset of obsolete pgdat from try_offline_node() to
>> hotadd_new_pgdat(), and just resetting pgdat->nr_zones and
>> pgdat->classzone_idx to be 0 rather than the whole reset by memset()
>> as Kame suggested.
>>
>> Regards,
>> Gu
>>
>> ---
>> mm/memory_hotplug.c | 13 ++++---------
>> 1 files changed, 4 insertions(+), 9 deletions(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 1778628..c17eebf 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1092,6 +1092,10 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
>> return NULL;
>>
>> arch_refresh_nodedata(nid, pgdat);
>> + } else {
>> + /* Reset the nr_zones and classzone_idx to 0 before reuse */
>> + pgdat->nr_zones = 0;
>> + pgdat->classzone_idx = 0;
>
> Hi Gu,
>
> This is just to avoid the warning, I think it's no meaning.
Can not agree.
The key point here is postponing the reset of obsolete pgdat to the time we
want to reuse it to avoid the effect(Oops: 0000 as you mentioned), and avoiding
warning is the minor benefit, though it is also important.
> Here is the changlog from the original patch:
>
> commit 88fdf75d1bb51d85ba00c466391770056d44bc03
> ...
> Warn if memory-hotplug/boot code doesn't initialize pg_data_t with zero
> when it is allocated. Arch code and memory hotplug already initiailize
> pg_data_t. So this warning should never happen. I select fields *randomly*
> near the beginning, middle and end of pg_data_t for checking.
> ...
There was not hot remove node that time, so it seems did not consider the *reuse*
case, but anyway, we should not break it here.
Regards,
Gu
>
> Thanks,
> Xishi Qiu
>
>> }
>>
>> /* we can use NODE_DATA(nid) from here */
>> @@ -2021,15 +2025,6 @@ void try_offline_node(int nid)
>>
>> /* notify that the node is down */
>> call_node_notify(NODE_DOWN, (void *)(long)nid);
>> -
>> - /*
>> - * Since there is no way to guarentee the address of pgdat/zone is not
>> - * on stack of any kernel threads or used by other kernel objects
>> - * without reference counting or other symchronizing method, do not
>> - * reset node_data and free pgdat here. Just reset it to 0 and reuse
>> - * the memory when the node is online again.
>> - */
>> - memset(pgdat, 0, sizeof(*pgdat));
>> }
>> EXPORT_SYMBOL(try_offline_node);
>>
>
>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@xxxxxxxxx. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
> .
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>