[LTP] [PATCH] cpuset_memory_spread: change lowerlimit to 5000kb

[Hongchen Zhang]

Hi Richard ,
   Thanks for your review,
On 2023/8/29 下午5:25, Richard Palethorpe wrote:
> Hello,
> 
> Hongchen Zhang <zhanghongchen@loongson.cn> writes:
> 
>> Hi Chril,
>> Any suggestion about this patch?
>>
>> On 2023/6/16 pm 6:13, Hongchen Zhang wrote:
>>> Hi Martin,
>>> On 2023/6/16 pm 5:31, Martin Doucha wrote:
>>>> On 16. 06. 23 4:10, Hongchen Zhang wrote:
>>>>> Hi Martin,
>>>>>
>>>>> On 2023/6/15 pm 10:27, Martin Doucha wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On 09. 06. 23 3:27, Hongchen Zhang wrote:
>>>>>>> When I test the cpuset_memory_spread case,this case FAIL too often.
>>>>>>> After dig into the code, I find out that the fowlloing things trigger
>>>>>>> the FAIL:
>>>>>>> 1) random events,the probability is very small and can be ignored
>>>>>>> 2) get_meminfo which before send signal to test_pid
>>>>>>> 3) account_memsinfo before result_check
>>>>>>>
>>>>>>> About 2) and 3), we can increase the value of lowerlimit to keep
>>>>>>> the result as SUCCESS.After my testing, 5000kb is a reasonable value.
>>>>>>
>>>>>> we're also seeing these failures but only on architectures like
>>>>>> PowerPC with pagesize higher than the usual 4KB. On which
>>>>>> architectures do you see failures and what's the pagesize there?
>>>>> I test on 3C5000+7A2000 machine, the architecture is LoongArch.The
>>>>> pagesize we used is 16KB.
>>>>
>>>> So the underlying cause is the same - higher pagesize. That means
>>>> the upperlimit, lowerlimit and DATAFILE size should be calculated
>>>> from pagesize instead.IMO,upperlimit and DATAFILE size will not
>>>> affect the result.
>>> Change the lowerlimit like following?
>>> lowerlimit = 2000kb*get_pagesize()/SIZE_4K;
> 
> This formula looks ok, but you need to scale the other values by the
> page size as well.
> 
> Also I would recommend ensuring all values are multiples of the page
> size because the kernel will round up to the nearest page
> size.
> 
> So lowerlimit = 4096 * 5 = 2048Kb
> or lowerlimit = 16384 * 5 = 8192Kb
> 
> Maybe the upperlimit should be 5 * lowerlimit? Because we want the
> gap/spread to get bigger too. I don't know if the DATAFILE needs to
> change in size it is already 500MB.
> 
> Alternatively you could just create a lookup table with values for each
> page size we have tested. e.g.
> 
> switch (get_pagesize()) {
>         case 4096: 2048Kb
>         case 16384: 8192Kb
>         default: ...
> }
> 
> This may be better if the values to do not scale linearly. Which is
> totally possible because the page size effects most things and there
> could be feedback loops.
> 
> Please submit another patch if you are still interested.
OK, let me send the V2 patch.
> 


-- 
Best Regards
Hongchen Zhang