Re: [LTP] [PATCH] Set tunable value of min_free_kbytes lower

[Shuang Qiu <shuang.qiu@oracle.com>]

On 08/29/2012 10:03 PM, Zhouping Liu wrote:
>
> ----- Original Message -----
>> From: "Zhouping Liu" <zliu@redhat.com>
>> To: "shuang qiu" <shuang.qiu@oracle.com>
>> Cc: ltp-list@lists.sourceforge.net
>> Sent: Monday, August 27, 2012 1:16:45 PM
>> Subject: Re: [LTP] [PATCH] Set tunable value of min_free_kbytes lower
>>
>>
>>
>> ----- Original Message -----
>>> From: "Zhouping Liu" <zliu@redhat.com>
>>> To: "shuang qiu" <shuang.qiu@oracle.com>
>>> Cc: ltp-list@lists.sourceforge.net
>>> Sent: Friday, August 24, 2012 4:11:41 PM
>>> Subject: Re: [LTP] [PATCH] Set tunable value of min_free_kbytes
>>> lower
>>>
>>>
>>>
>>> ----- Original Message -----
>>>> From: "shuang qiu" <shuang.qiu@oracle.com>
>>>> To: ltp-list@lists.sourceforge.net
>>>> Sent: Thursday, August 23, 2012 2:43:01 PM
>>>> Subject: [LTP] [PATCH] Set tunable value of min_free_kbytes lower
>>>>
>>>> From: Shuang Qiu <shuang.qiu@oracle.com>
>>>>
>>>> The value of min_free_kbytes is set too high(half of mem_free)
>>>> during
>>>> testing min_free_kbytes tunable.It often cause the system to
>>>> become
>>>> out-of-memory.Using 20% of mem_free to avoid oom and system hang.
>>> Hi, shuang
>>>
>>> I met the issue that min_free_kbytes caused system hang before, and
>>> what you said made sense.
>> For the issue that min_free_kbytes caused system hang, I prepared a
>> patch for it,
>> at the same time, in order to enlarge the case's coverage, I add a
>> new case(2x default_tune)
>> I have tested it in my box, it's good.
>>
>> Shuang, can you review and test the patch?
>>
>> diff --git a/testcases/kernel/mem/tunable/min_free_kbytes.c
>> b/testcases/kernel/mem/tunable/min_free_kbytes.c
>> index 00ead04..ded0e45 100644
>> --- a/testcases/kernel/mem/tunable/min_free_kbytes.c
>> +++ b/testcases/kernel/mem/tunable/min_free_kbytes.c
>> @@ -10,7 +10,8 @@
>>    * the current free memory with the tunable value repeatedly.
>>    *
>>    * a) default min_free_kbytes with all overcommit memory policy
>> - * b) half of mem_free with all overcommit memory policy
>> + * b) 2x default value with all overcommit memory policy
>> + * c) 10% of MemFree or %5 MemTotal with all overcommit memory
> Hi, Shuang
>
> after setting 10% of MemFree or 5% MemTotal, it still cause a system
> hang, which has 16Gb memory. so I adjusted the value, reduced the value
> to 5% of MemFree or 2% MemTotal, which I think is more reasonable.
OK.
Thanks.
>
> Thanks,
> Zhouping
>
>> policy
>>    *
>>    ********************************************************************
>>    * Copyright (C) 2012 Red Hat, Inc.
>> @@ -115,20 +116,27 @@ int main(int argc, char *argv[])
>>   static void test_tune(unsigned long overcommit_policy)
>>   {
>>          int status;
>> -       int pid[2];
>> +       int pid[3];
>>          int ret, i;
>> -       unsigned long tune, memfree;
>> +       unsigned long tune, memfree, memtotal;
>>   
>>          set_sys_tune("overcommit_memory", overcommit_policy, 1);
>>   
>> -       for (i = 0; i < 2; i++) {
>> +       for (i = 0; i < 3; i++) {
>>                  /* case1 */
>>                  if (i == 0)
>>                          set_sys_tune("min_free_kbytes", default_tune,
>>                          1);
>>                  /* case2 */
>> -               else {
>> +               else if (i == 1) {
>> +                       set_sys_tune("min_free_kbytes", 2 *
>> default_tune, 1);
>> +               /* case3 */
>> +               } else {
>>                          memfree = read_meminfo("MemFree:");
>> -                       tune = memfree / 2;
>> +                       memtotal = read_meminfo("MemTotal:");
>> +                       tune = memfree / 10;
>> +                       if (tune > (memtotal / 20))
>> +                               tune = memtotal / 20;
>> +
>>                          set_sys_tune("min_free_kbytes", tune, 1);
>>                  }
>>   
>>
>>
>>> but after tested the patch, I found it still make the system hang
>>> with the patch, so I don't think
>>> this patch can fix the issue completely, maybe there are other
>>> factors, or need lower tune value.
>>> always suppose it was because of the high tune value, it's more
>>> better to add an optional to control it.
>>> also I will investigate it deeper to look after the real reason.
>>> please comment if you have other ideas.
>>>
>>> Thanks,
>>> Zhouping
>>>
>>>> ---
>>>>   testcases/kernel/mem/tunable/min_free_kbytes.c |    2 +-
>>>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/testcases/kernel/mem/tunable/min_free_kbytes.c
>>>> b/testcases/kernel/mem/tunable/min_free_kbytes.c
>>>> index 00ead04..8a03f85 100644
>>>> --- a/testcases/kernel/mem/tunable/min_free_kbytes.c
>>>> +++ b/testcases/kernel/mem/tunable/min_free_kbytes.c
>>>> @@ -128,7 +128,7 @@ static void test_tune(unsigned long
>>>> overcommit_policy)
>>>>   		/* case2 */
>>>>   		else {
>>>>   			memfree = read_meminfo("MemFree:");
>>>> -			tune = memfree / 2;
>>>> +			tune = memfree / 5;
>>>>   			set_sys_tune("min_free_kbytes", tune, 1);
>>>>   		}
>>>>   
>>>> --
>>>> 1.7.7
>>>>
>>>>
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>> --
>> Thanks,
>> Zhouping
>>



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