linux-kernel - Re: Kernel falls apart under light memory pressure (i.e. linking vmlinux)

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Date:	Tue, 24 May 2011 10:34:21 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andrew Lutomirski <luto@....edu>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	fengguang.wu@...el.com, andi@...stfloor.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mgorman@...e.de, hannes@...xchg.org,
	riel@...hat.com
Subject: Re: Kernel falls apart under light memory pressure (i.e. linking vmlinux)

On Tue, May 24, 2011 at 10:19 AM, Andrew Lutomirski <luto@....edu> wrote:
> On Sun, May 22, 2011 at 7:12 PM, Minchan Kim <minchan.kim@...il.com> wrote:
>> Could you test below patch based on vanilla 2.6.38.6?
>> The expect result is that system hang never should happen.
>> I hope this is last test about hang.
>>
>> Thanks.
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 292582c..1663d24 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -231,8 +231,11 @@ unsigned long shrink_slab(struct shrink_control *shrink,
>>       if (scanned == 0)
>>               scanned = SWAP_CLUSTER_MAX;
>>
>> -       if (!down_read_trylock(&shrinker_rwsem))
>> -               return 1;       /* Assume we'll be able to shrink next time */
>> +       if (!down_read_trylock(&shrinker_rwsem)) {
>> +               /* Assume we'll be able to shrink next time */
>> +               ret = 1;
>> +               goto out;
>> +       }
>>
>>       list_for_each_entry(shrinker, &shrinker_list, list) {
>>               unsigned long long delta;
>> @@ -286,6 +289,8 @@ unsigned long shrink_slab(struct shrink_control *shrink,
>>               shrinker->nr += total_scan;
>>       }
>>       up_read(&shrinker_rwsem);
>> +out:
>> +       cond_resched();
>>       return ret;
>>  }
>>
>> @@ -2331,7 +2336,7 @@ static bool sleeping_prematurely(pg_data_t
>> *pgdat, int order, long remaining,
>>        * must be balanced
>>        */
>>       if (order)
>> -               return pgdat_balanced(pgdat, balanced, classzone_idx);
>> +               return !pgdat_balanced(pgdat, balanced, classzone_idx);
>>       else
>>               return !all_zones_ok;
>>  }
>
> So far with this patch I can't reproduce the hang or the bogus OOM.
>
> To be completely clear, I have COMPACTION, MIGRATION, and THP off, I'm
> running 2.6.38.6, and I have exactly two patches applied.  One is the
> attached patch and the other is a the fpu.ko/aesni_intel.ko merger
> which I need to get dracut to boot my box.
>
> For fun, I also upgraded to 8GB of RAM and it still works.
>

Hmm. Could you test it with enable thp and 2G RAM?
Isn't it a original test environment?
Please don't change test environment. :)

Thanks for your effort, Andrew.

-- 
Kind regards,
Minchan Kim
--
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