Re: [Xen-devel] New Outreachy Applicant

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 03/10/16 06:14, Ronald Rojas wrote:
> On Tue, Sep 20, 2016 at 04:24:47PM +0100, George Dunlap wrote:
>> Thanks for your interest in the Xen Project!  Sorry for the delay in
>> responding -- somehow your mail either never made it to my personal
>> inbox or I accidentally deleted it instead of filing it properly.  I
>> saw your question on IRC and now found your mail here on xen-devel.
>>
>> First, I want to emphasize that Outreachy internships should be
>> considered a full-time job.  As part of the application process you
>> will be asked to confirm that you will not be taking any classes, nor
>> have any other significant commitments (such as another job) during
>> the period of the internship.
> 
> I'll confirm now that won't be taking any classes or working during the
> majority of the program, however the fall semester for my college will
> end around the 20th of December. 
>>
>> Now on to the bite-sized task.  We've actually found that one of the
>> difficult parts of getting going with our project is making sure that
>> you understand how to get your whole system and environment set up.
>> And another thing we want to see is to what degree you can balance
>> figuring things out, finding the answers on the web, and asking for
>> help when you need it.
>>
>> So with that in mind, we've started experimenting with tasks which
>> don't contribute very much to the project directly, but provide a
>> really solid base of knowledge to do further contributions.
>>
>> So here's my challenge for you.
>>
>> -------
>> OUTCOME
>>
>> Write a simple go program that will list the current cpu pools,
>> similar to the output of "xl cpupool-list".  No need to handle extra
>> arguments or modify libxl.go (beyond what may be needed to compile it).
> 
> RESULTS:
> I've managed to get xen running on my local machine. I am running linux 
> natively
> on ubuntu with xen 4.8-unstable and it is running reasonable well.
> There are two VM's running on my computer, one is named tutorial-pv-guest 
> that I
> created by following the xen beginners guide. The other is called ubuntu1 and
> was created through a custom configuration file that I created. I wasn't 
> having
> much luck with the outreachy tutorial provided so after some googling the 
> link 
> below really helped me get through the process.
> 
> http://www.virtuatopia.com/index.php/Building_a_Xen_Guest_Domain_using_Xen-Tools
> 
>>
>> Please post a copy of your .go program, along with the results of
>> output *when more than one VM is running*.
> 
> The output when I run "sudo go run libxl.go" is pasted below. The output was 
> made 
> when the two VM's mentioned above were running. It prints out the appropiate 
> output for Pool Name, Scheduler, and Domain Count. 
> All the changes in libxl.go are contained within the main() method and the 
> libxl.go
> file is pasted below as well.

Looks good, thank you!

> CONCERNS/QUESTIONS:
> I believe I was only able to print out the information for Name, Sched, and 
> Domain 
> count because the other information such as Active and CPU's are not stored 
> within
> CpupoolInfo. Was there a way I could obtain that information? I don't think 
> the 
> code privided had that functionality. Maybe the next task could be to add 
> that 
> functionality?

It looks like "cpus" is done by actually counting the bits in the cpu
bitmask, which was not (yet) implemented in the code that I sent you.  I
have since implemented bitmaps in my copy, but not yet a method to
automatically count how many bits are set.

I just looked at the xl implementation of 'cpupool-list', and discovered
that the line which prints the cpupool information looks like this:

                printf("%3d %9s       y       %4d", n,
                       libxl_scheduler_to_string(poolinfo[p].sched),
                       poolinfo[p].n_dom);

In other words, the "Active" field is totally bogus --  the format
string itself just prints 'y'!

> It also seems that Domain Count is off. The command "xl cpupool-list" lists 3 
> domains
> (which are Dom0, tutorial-pv-guest, and ubuntu1) but my program returns 11 
> domains. 
> Would you like me to look into the issue? I'm using the information called 
> from 
> Ctx.ListCpupool() so I may have to take a closer look at that code. 

Actually I think you just have a typo in your program. :-)

Thanks for this -- if you're up for it, let me see what kinds of next
steps you can do (obviously when you have the opportunity).

 -George

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