linux-kernel - Re: [PATCH] Fix the issue that lowmemkiller fell into a cycle that try to kill a task

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Date:	Tue, 23 Sep 2014 04:48:55 +0000
From:	朱辉 <zhuhui@...omi.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	"rientjes@...gle.com" <rientjes@...gle.com>,
	"vinayakm.list@...il.com" <vinayakm.list@...il.com>,
	"weijie.yang@...sung.com" <weijie.yang@...sung.com>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"teawater@...il.com" <teawater@...il.com>
Subject: Re: [PATCH] Fix the issue that lowmemkiller fell into a cycle that
 try to kill a task



On 09/23/14 12:18, Greg KH wrote:
> On Tue, Sep 23, 2014 at 10:57:09AM +0800, Hui Zhu wrote:
>> The cause of this issue is when free memroy size is low and a lot of task is
>> trying to shrink the memory, the task that is killed by lowmemkiller cannot get
>> CPU to exit itself.
>>
>> Fix this issue with change the scheduling policy to SCHED_FIFO if a task's flag
>> is TIF_MEMDIE in lowmemkiller.
>>
>> Signed-off-by: Hui Zhu <zhuhui@...omi.com>
>> ---
>>   drivers/staging/android/lowmemorykiller.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
>> index b545d3d..ca1ffac 100644
>> --- a/drivers/staging/android/lowmemorykiller.c
>> +++ b/drivers/staging/android/lowmemorykiller.c
>> @@ -129,6 +129,10 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
>>
>>   		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
>>   		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
>> +			struct sched_param param = { .sched_priority = 1 };
>> +
>> +			if (p->policy == SCHED_NORMAL)
>> +				sched_setscheduler(p, SCHED_FIFO, &param);
>
> This seems really specific to a specific scheduler pattern now.  Isn't
> there some other way to resolve this?

I tried to let the task that call lowmemkiller sleep some time when it 
try to kill same task.  But it doesn't work.
I think the issue is that the free memroy size is too low to make more 
and more tasks come to call lowmemkiller.

Thanks,
Hui

>
> thanks,
>
> greg k-h
>