Re: Compiler memory consumption

[Ludovic Courtès]

Heya,

Andy Wingo <address@hidden> skribis:

>> Also, for reference, loading python.go peaks at 315M RSS:
>>
>> $ \time ./pre-inst-env guile -c '(use-modules (gnu packages python))'
>> 0.18user 0.02system 0:00.18elapsed 112%CPU (0avgtext+0avgdata 
>> 315648maxresident)k
>> 0inputs+0outputs (0major+7784minor)pagefaults 0swaps
>
> But this I don't understand.  If I do a ./pre-inst-env guile and then
> load (gnu packages python), I get a 20MB heap size, a 35MB total private
> dirty memory and 52MB clean shared memory.  (Measured using smaps via
> https://wingolog.org/pub/mem_usage.py).  This is at commit
> 60c9e80444421c412ae3d0e7b4b224ef0e32947f.
>
> I just built the "time" package and I see similar numbers here.  I can
> only think that the "time" package's numbers are bogus.

As discussed on IRC, I just checked and ‘time’ uses the ‘wait3’ syscall
to get the process’s resource usage info once it has completed.  In
libc.info it’s described like this:

     ‘long int ru_maxrss’
          The maximum resident set size used, in kilobytes.  That is,
          the maximum number of kilobytes of physical memory that
          PROCESSES used simultaneously.

>> When compiling python.scm #:to 'cps, we end up with 1G max RSS in 6s.
>
> Measured with time?  If this is the case it could be that python.scm is
> just a lot of code.  Any compiler would take a lot if the IR size is 1
> GB.
>
>> The only conclusion I can draw is that cps-to-bytecode compilation seems
>> to be responsible for most of the memory consumption.
>
> This is possible but I am not there yet.  I don't see why compiling this
> file to CPS should cause memory usage of 1GB.  That is 9000 memory words
> per textual line -- simply too much.
>
> Many unknowns here!

Yes.  :-/

Ludo’.