Re: problem with ZONE_MOVABLE.

[Balbir Singh <balbir@linux.vnet.ibm.com>]

Mel Gorman wrote:
> On (13/09/07 19:07), KAMEZAWA Hiroyuki didst pronounce:
>> Hi, 
>>
>> While I'm playing with memory controller of 2.6.23-rc4-mm1, I met following.
>>
>> ==
>> [root@drpq test-2.6.23-rc4-mm1]# echo $$ > /opt/mem_control/group_1/tasks
>> [root@drpq test-2.6.23-rc4-mm1]# cat /opt/mem_control/group_1/memory.limit
>> 32768
>> [root@drpq test-2.6.23-rc4-mm1]# cat /opt/mem_control/group_1/memory.usage
>> 286
>> // Memory is limited to 512 GiB. try "dd" 1GiB (page size is 16KB)
>>  
>> [root@drpq test-2.6.23-rc4-mm1]# dd if=/dev/zero of=/tmp/tmpfile bs=1024 count=1048576
>> Killed
>> [root@drpq test-2.6.23-rc4-mm1]# ls
>> Killed
>> //above are caused by OOM.
>> [root@drpq test-2.6.23-rc4-mm1]# cat /opt/mem_control/group_1/memory.usage
>> 32763
>> [root@drpq test-2.6.23-rc4-mm1]# cat /opt/mem_control/group_1/memory.limit
>> 32768
>> // fully filled by page cache. no reclaim run.
>> ==
>>
>> The reason  this happens is  because I used kernelcore= boot option, i.e
>> ZONE_MOVABLE. Seems try_to_free_mem_container_pages() ignores ZONE_MOVABLE.
>>
>> Quick fix is attached, but Mel's one-zonelist-pernode patch may change this.
>> I'll continue to watch.
>>
> 
> You are right on both counts. This is a valid fix but
> one-zonelist-pernode overwrites it. Specifically the code in question
> with one-zonelist will look like;
> 
> 	for_each_online_node(node) {
> 		zonelist = &NODE_DATA(node)->node_zonelist;
> 		if (do_try_to_free_pages(zonelist, sc.gfp_mask, &sc))
> 			return 1;
> 	}
> 
> We should be careful that this problem does not get forgotten about if
> one-zonelist gets delayed for a long period of time. Have the fix at the
> end of the container patchset where it can be easily dropped if
> one-zonelist is merged.
> 
> Thanks

Yes, I second that. So, we should get KAMEZAWA's fix in.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL

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