[LTP] [PATCH] cpuset_inherit: Use the original mem value instead of N_NODES

[Yang Xu]

Hi Cyril
> Hi!
>> When I look these cpuset cases(cpuset_base_ops_test,
>> cpuset_hierarchy_test, cpuset_inherit_test...), these cases seems all
>> not consider the situation(cpus/memory are not numbered continously). If
>> we want to modify them to be situable for not numbered continously, it
>> will be complexd(especially cpuset_base_ops_test).
>
> Thats why I said that these tests would need to be rewritten ideally
> from a scratch. I guess that it would be easier to work with bitfields
> in C as well.
>
I see.
>> AFAIK, I rarely see not numbered continously for memory node. IMO, we
>> just check whether memory/cpu numbered continously, if not, we just
>> report TCONF and remind user to change their system to meet
>> environment, so their system can be fully tested.
>
> That would be better than unexpected failure at least.
>
Since we are just before a release, I think using this way is ok. I will 
send a patch for this soon.
>> For cpu, maybe we can use the following script to detect
>>
>> cpu_string="`cat /sys/devices/system/cpu/online`"
>> offline_string="`cat /sys/devices/system/cpu/online`"
>> NR_CPUS=`tst_ncpus`
>> ALL_CPUS=`tst_ncpus_conf`
>> if [ $NR_CPUS -eq $ALL_CPUS ]; then
>>          tst_resm TINFO "All($ALL_CPUS) logical cpus on your environment"
>> else
>>         tst_brkm TCONF "Not all logical cpus on, online($cpu_string),offline($offline_string)"
>> fi
>>
>> I wonder if it's worth changing the stable cpuset/memory cases for these
>> rared situation(memory/cpu are not numbered continously).
>
> It would allow us to offline CPUs in the middle of the test and checking
> that offlined CPUs can no longer be added into the mask, which is
> something we cannot test at the moment.
 From this point, it is meaningful.
>
>> What do you think about it?
>
> To be honest I'm not sure if ncpus == ncpus_conf means that the cpu
> numbering is continous.
I see ltp/lib/tst_cpu.c uses 
_SC_NPROCESSORS_ONLN/_SC_NPROCESSORS_CONF[1] sysconf. if ncpus == 
ncpus_conf, it means all cpu enable so the cpu numbering must be continous.

[1]https://www.gnu.org/software/libc/manual/html_node/Processor-Resources.html
>
> I guess that the safest bet would be actually parsing the
> /sys/devices/system/cpu/online instead. I.e. check that the file is in a
> format 0-$(UINT), since that is what the testcases do expect, right?
Yes.
my old way (using _SC_NPROCESSORS_ONLN/_SC_NPROCESSORS_CONF[1] macro) is 
to detect all logcial cpu enabled, your way can cover more situation.
>
>> +#select the first one or two online cpu
>> +select_online_cpus()
>> +{
>> +	ncpus_check ${1:-2}
>> +	local cpus_array="$(seq -s' ' 0 $((ALL_CPUS-1)))"
>> +	local cpuid=
>> +	local iter=0
>> +	for cpuid in $cpus_array
>> +	do
>> +		local file="/sys/devices/system/cpu/cpu$cpuid/online"
>> +		local online="$(cat $file)"
>> +		if [ $online -eq 1 ]; then
>> +			iter=`expr $iter + 1`
>> +			if [ $iter -eq 1 ]; then
>> +				F_ONELINE_CPU=$cpu_id
>> +			elif [ $iter -eq 2 ]; then
>> +				S_ONLINE_CPU=$cpu_id
>> +			else
>> +				break
>> +			fi
>> +		fi
>> +        done
>> +}
>
> Bitfields are akward in shell. So if I was writing these tests I would
> write a function to parse the sysfs file into a cpuset bitfield and
> second function to write the bitfield into a sysfs file. And after that
> we would do all the operations on cpuset bitfields instead.
>
> That way we can, for instance, get any subset of online CPUs easily,
> since that is just one loop over the cpuset bitfield.
Agree.
>
> e.g. to get a subset with half of the online CPUs we would do:
>
> 	int flag = 0, i;
>
> 	for (i = 0; i<  setsize; i++) {
> 		if (CPU_ISSET_S(i, setsize, inset)) {
> 			if (flag)
> 				GPU_SET_S(i, setsize, outset);
>
> 			flag = !flag;
> 		}
> 	}
>
> We can probably reuse the code kernel uses to parse and print these, the
> code to print a bitmap seems to be in bitmap_list_string() in
> lib/vsprintf.c, the parsing seems to be implemented in
> bitmap_parselist_user() in the lib/bitmap.c.
I will see these code when I am free.
>