Re: Rust frontend patches v3

[David Malcolm <dmalcolm@redhat.com>]

On Fri, 2022-10-28 at 17:20 +0200, Arthur Cohen wrote:
> 
> 
> On 10/28/22 15:06, David Malcolm wrote:
> > On Fri, 2022-10-28 at 13:48 +0200, Arthur Cohen wrote:
> > > Hi David,
> > > 
> > > On 10/26/22 23:15, David Malcolm wrote:
> > > > On Wed, 2022-10-26 at 10:17 +0200,
> > > > arthur.cohen@embecosm.com wrote:
> > > > > This is the fixed version of our previous patch set for gccrs
> > > > > -
> > > > > We've
> > > > > adressed
> > > > > the comments raised in our previous emails.

[...snip...]

> > 
> > I'm guessing that almost all of gccrs testing so far has been on
> > relatively small examples, so that even if the GC considers
> > collecting,
> > the memory usage might not have exceeded the threshold for actually
> > doing the mark-and-sweep collection, and so no collection has been
> > happening during your testing.
> > 
> > In case you haven't tried yet, you might want to try adding:
> >    --param=ggc-min-expand=0 --param=ggc-min-heapsize=0
> > which IIRC forces the GC to actually do its mark-and-sweep
> > collection
> > at every potential point where it might collect.
> 
> That's very helpful, thanks a lot. I've ran our testsuite with these
> and 
> found no issues, but we might consider adding that to our CI setup to
> make sure.

Great!   Though as noted, for libgccjit it slows the testsuite down
*massively*, so you might want to bear that in mind.  I'm doing it for
libgccjit because libgccjit looks like a "frontend" to the rest of the
GCC codebase, but it's a deeply weird one, and so tends to uncover
weird issues :-/

Dave

> 
> Kindly,
> 
> Arthur
> 
> > I use these params in libgccjit's test suite; it massively slows
> > things
> > down, but it makes any GC misuse crash immediately even on minimal
> > test
> > cases, rather than hiding problems until you have a big (and thus
> > nasty) test case.
> > 
> > Hope this is helpful
> > Dave
> > 
> > 
> > > 
> > > > Hope this is constructive
> > > > Dave
> > > > 
> > > 
> > > Thanks a lot for the input,
> > > 
> > > All the best,
> > > 
> > > Arthur
> > > 
> > > 
> > > 
> > > 
> >