linux-kernel - Re: [RFC] oom, but there is enough memory

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Date:	Thu, 31 Mar 2016 17:38:06 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Michal Hocko <mhocko@...nel.org>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] oom, but there is enough memory

On 2016/3/31 17:30, Michal Hocko wrote:

> On Thu 31-03-16 17:16:00, Xishi Qiu wrote:
>> It triggers a lot of ooms, but there is enough memory(many large blocks).
>> And at last "Kernel panic - not syncing: Out of memory and no killable processes..."
>>
>> I find almost the every call trace include "pagefault_out_of_memory" and "gfp_mask=0x0".
>> If it does oom, why not it triger in mm core path? 
> 
> It seems that somebody in the page fault path has returned with
> VM_FAULT_OOM without invoking the page allocator and kept returning the
> same error until there is nothing killable and so the oom killer panics.
> 
> [...]
>> <4>[63651.040374s][pid:2912,cpu3,sh]DMA free:550600kB min:5244kB low:27580kB high:28892kB active_anon:343060kB inactive_anon:1224kB active_file:107596kB inactive_file:465156kB unevictable:1040kB isolated(anon):0kB isolated(file):0kB present:2016252kB managed:1720040kB mlocked:1040kB dirty:40kB writeback:0kB mapped:200420kB shmem:1312kB slab_reclaimable:27048kB slab_unreclaimable:73300kB kernel_stack:15248kB pagetables:14484kB unstable:0kB bounce:0kB free_cma:30896kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
> 
> This is rather weird. DMA zone with 2GB? What kind of architecture is
> this?

Hi Michal,

It's arm64, so DMA is [0-4G], and Normal is [4G-]
Is that something wrong with the RAM hardware, then trigger the problem?

Thanks,
Xishi Qiu