Re: Tracking page allocation in Zone/Node

[Bob Liu <lliubbo@gmail.com>]

On Mon, Aug 15, 2011 at 1:01 PM, Pintu Agarwal <pintu_agarwal@yahoo.com> wrote:
> Thanks Christoph for your reply :)
>
>> Weird system. One would expect it to only have NORMAL zones. Is this an
>> ARM system?
>
> Yes this is an ARM based system for linux mobile phone.
>
>> I am not sure that I understand you correctly but you can get the data from node 2 via
>> zone_page_state(NODE_DATA[2]->node_zones[ZONE_DMA], NR_FREE_PAGES);
>
> Yes, you got me right. I wanted to access Node 2 data from the preferred zone. This is helpful, thanks.
> But I want it to be dynamic. That is if Node 2 is over-loaded, then the allocation happens from Node 1 or Node 0 as well.

In my opinion, current code will do this behavior.
If allocation from node 2 failed, it will try other nodes, so you
needn't to do it by yourself.

> Also it should work on normal desktop itself where there are DMA, Normal, HighMem as well.
> How to make the above statement generic so that it should work in all scenarios?
>
>> or in __alloc_pages_nodemask
>> zone_page_state(preferred_zone, NR_FREE_PAGES);
>
> Yes, I tried exactly like this, but since I have only one zone (DMA), it always returns me the data from the first Node 0.
> This will only work, if I have 3 separate zones (DMA, Normal, HighMem)
>
> In "__alloc_pages_nodemask", before the actual allocation happens, how to find out the allocation is going to happen from which zone and which Node.?
> (The _preferred_zone_ info is not enough, I need to know the Node number as well)
>
> Please help...
> I hope the question is clear know.
>
>
>
> Thanks,
> Pintu
>
>
> ----- Original Message -----
> From: Christoph Lameter <cl@linux.com>
> To: Pintu Agarwal <pintu_agarwal@yahoo.com>
> Cc: "mgorman@suse.de" <mgorman@suse.de>; "linux-mm@kvack.org" <linux-mm@kvack.org>
> Sent: Friday, 12 August 2011 9:38 PM
> Subject: Re: Tracking page allocation in Zone/Node
>
> On Fri, 12 Aug 2011, Pintu Agarwal wrote:
>
>> On my system I have only DMA zones with 3 nodes as follows:
>> Node 0, zone      DMA      3      4      6      4      5      0      0      0      0      0      0
>> Node 1, zone      DMA      8      4      3      8      7      4      2      0      0      0      0
>> Node 2, zone      DMA     10      2      8      3      2      2      4      1      2      2     28
>
> Weird system. One would expect it to only have NORMAL zones. Is this an
> ARM system?
>
>
>> In __alloc_pages_nodemask(...), just before "First Allocation Attempt" [that is before get_page_from_freelist(....)], I wanted to print all the free pages from the "preferred_zone".
>> Using something like this :
>> totalfreepages = zone_page_state(zone, NR_FREE_PAGES);
>>
>> But in my case, there is only one zone (DMA) but 3 nodes.
>> Thus the above "zone_page_state" always returns totalfreepages only from first Node 0.
>> But the allocation actually happening from Node 2.
>>
>> How can we point to the zone of Node 2 to get the actual value?
>>
>
>
> I am not sure that I understand you correctly but you can get the data
> from node 2 via
>
> zone_page_state(NODE_DATA[2]->node_zones[ZONE_DMA], NR_FREE_PAGES);
>
> or in __alloc_pages_nodemask
>
> zone_page_state(preferred_zone, NR_FREE_PAGES);
>
>

-- 
Regards,
--Bob

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