[Vm-dev] Measuring allocations

[Levente Uzonyi]

You should be able do that in your image by replacing #basicNew, 
#basicNew: and #shallowCopy with method wrappers which would sum up the 
size of the allocated objects in ProcessLocalVariables before returning 
the new objects.

Levente

On Thu, 1 Jun 2017, Jan Vrany wrote:

> 
> On Thu, 2017-06-01 at 07:52 -0700, Eliot Miranda wrote:
>>  
>> Hi Jan,
>> 
>> > On Jun 1, 2017, at 1:17 AM, Jan Vrany <jan.vrany at fit.cvut.cz>
>> > wrote:
>> > 
>> > 
>> > Hi folks, 
>> > 
>> > Having a Spur VM, I wonder how to measure heap allocations made 
>> > by a process executing a particular block, from within the image. 
>> > For example, let's have following block: 
>> > 
>> > [
>> >   | a |
>> > 
>> >   100 timesRepeat: [
>> >      a := Array new: 100 
>> >   ]
>> > ]. 
>> > 
>> > When run, this block allocates - if I'm correct - some 100 *
>> > (<object
>> > header size> + 4*100) bytes. 
>> 
>> Plus the block arg to timesRepeat:.  And the size of an Array in 32-
>> bits is
>> 
>
> Sure, sure. The exact number is not important for me right now.
>
>> > Note that: 
>> > * Ideally, I'd like to exclude allocations made by other threads 
>> 
>> Then run at high priority.
>
> Good point, thanks. I always forget about that. 
>
>> 
>> >   but having allocations made by all threads would be OK too. 
>> > * Block can span multiple scavenges even oldspace collects. 
>> > * As shown in the example above, I need to take garbage into 
>> >   an account.
>> > 
>> > How to best measure this? 
>> 
>> What exactly do you want to measure? 
>
> I want to know how much given code allocates. For example that
> given piece of code in total allocated 2.5GB. Say. 
>
>
>>  There is no allocation count, as that would slow down allocation. 
>
> Fair enough. 
>
>>  Time taken to allocate  would be derived by sending timeTiRun to the
>> above and subtracting the time for a null loop to run, and the time
>> taken in GC.
>> 
>> The time taken in GC is maintained by the vm.  See vmParameterAt: and
>> surrounding.  If you open the About Squeak dialog in a Squeak image
>> this is nicely displayed in the VM Stats tab (IIRC).
>
> It is indeed. But in this case I'm not interested in time spent in GC 
> :-) 
>
> Thanks, Jan