[Glass] Problem with #fork and #performOnServer?

[Petr Fischer via Glass]

 am interested also in this: in free Gemstone version, all Gemstone processes has CPU affinity to first 2 CPU cores (licensing).
 Does this also apply for your own sub-processes (performOnServer: or OSSubprocess)?

 In Free version is possible to run 10-20 Gems, but only on 2 cores, quite a bottleneck...

 pf


> On Mon, Jul 3, 2017 at 4:52 PM, Petr Fischer via Glass <
> glass at lists.gemtalksystems.com> wrote:
> 
> > > Hi guys,
> > >
> > > I am trying to accomplish something easy: I have a main gem that iterates
> > > some "reports" and exports each report into a PDF by calling a unix lib.
> > > This PDF export takes some seconds. So what I wanted to do is something
> > > like this pseudo code:
> > >
> > > self reports do: [:aReport | [  System performOnServer: (self
> > > pdfExportStringFor: aReport)  ] fork ].
> > >
> > > What I wanted to do with that is that each unix process for the PDF tool
> > > was executed on separate CPU cores than the GEM (my current GemStone
> > > license does allow all cores). However, I am not sure I am getting that
> > > behavior. It looks like I am still using 1 core and being sequential.
> > >
> > > Finally, I couldn't even reproduce a single test case with that I had in
> > > mind:
> > >
> > > 1 to: 6 do: [:index |
> > > [ System performOnServer: 'tar -zcvf test', index asString, '.tar.gz
> > > /home/quuve/GsDevKit_home/server/stones/xxx_333/extents' ] fork.
> > > ].
> > >
> > > I would have expected those lines to burn my server and use 6 cpu cores
> > at
> > > 100%. But no, nothing happens. What is funny is that if I call the very
> > > same line without the #fork I do get the 100% CPU process:
> >
> > Just a note:
> > tar/gzip is not written with multicore support IMHO, so you always utilize
> > single core only to 100%. But there is "parallel gzip" (pigz), which
> > definitelly turns CPU cooler to speed.
> > Usage: tar --use-compress-program=pigz ...
> >
> 
> Sure, that was a dummy example to see CPU in usage and test my thoughts
> (not the real unix command called)
> 
> 
> >
> > Is performOnServer: really non blocking for whole image/gem (or the whole
> > VM simply wait for command to complete)?
> >
> >
> Yeah, that's the thing, I think you are right, the #performOnServer: may be
> blocking at gem level.
> 
> For OSSubprocess I was able to allow specifying/managing none blocking
> pipes for standard streams.
> 
> And now, I am reading GsHostProcess and it also supports none blocking
> streams!!
> 
> I see that #_waitChild does indeed call waitpid() so.... I should be able
> to do a busy waiting around #childHasExited
> 
> BTW,  for OSSubprocesses I added a SIGCHLD kind of waiting to avoid
> polling.... but of course, you must be careful because you may need to
> force reading from streams (depending on how much the process writes)
> 
> [2]
> https://github.com/marianopeck/OSSubprocess#semaphore-based-sigchld-waiting
> 
> 
> Thanks!
> 
> -- 
> Mariano
> http://marianopeck.wordpress.com