Re: [cocci] Very long compile times on parsing_cocci/parser_cocci_menhir.ml

["Richard W.M. Jones" <rjones@redhat.com>]

On Thu, May 02, 2024 at 06:39:34PM +0200, Julia Lawall wrote:
> 
> 
> On Thu, 2 May 2024, Richard W.M. Jones wrote:
> 
> > On Thu, May 02, 2024 at 11:44:00AM +0200, Julia Lawall wrote:
> > >
> > >
> > > On Thu, 2 May 2024, Richard W.M. Jones wrote:
> > >
> > > > OCAMLOPT  parsing_cocci/parser_cocci_menhir.ml
> > > >
> > > > This single file takes a very long time to compile, about 34 minutes
> > > > on my 2 year old Intel laptop.  It's quite large too ...
> > > >
> > > > 139201 ./coccinelle-1.2/parsing_cocci/parser_cocci_menhir.ml
> > > >
> > > > I've observed in the past that the OCaml compiler doesn't handle
> > > > single large files well.  It seems to have some O(n^k) behaviour.
> > > >
> > > > Is this a known issue?
> > >
> > > I agree that it's slow, but I haven't seen it take 34 minutes.
> >
> > I just tried it on a much faster AMD desktop machine, but essentially
> > the same OCaml and menhir, and it still takes a very long time to
> > compile this one file: 17:35 minutes
> >
> > I tried it on a (different) machine with OCaml 4.11.1 and that was
> > considerably faster, taking under a minute.
> 
> I tried it on an Intel server and it takes a few seconds.  OCaml version
> 5.1.1.  menhir, version 20200123

Interesting, thanks Julia.  I'll poke this further to see
if I can find out what the causative factor is.

Rich.

> julia
> 
> >
> > Rich.
> >
> > > The point is that it is a parser, so the code is generated.  I use OCaml
> > > 4.13.1 or 5.0, not 5.1.1.  I have the same version of menhir as the one
> > > you mention.
> > >
> > > I can try to make it smaller.
> > >
> > > julia
> > >
> > > >
> > > > Rich.
> > > >
> > > > coccinelle 1.2 from tarball
> > > > ocaml-5.1.1-4.fc40.x86_64
> > > > ocaml-menhir-20231231-3.fc40.x86_64
> > > >
> > > > --
> > > > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> > > > Read my programming and virtualization blog: http://rwmj.wordpress.com
> > > > virt-top is 'top' for virtual machines.  Tiny program with many
> > > > powerful monitoring features, net stats, disk stats, logging, etc.
> > > > http://people.redhat.com/~rjones/virt-top
> > > >
> > > >
> >
> > --
> > Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
> > Read my programming and virtualization blog: http://rwmj.wordpress.com
> > virt-top is 'top' for virtual machines.  Tiny program with many
> > powerful monitoring features, net stats, disk stats, logging, etc.
> > http://people.redhat.com/~rjones/virt-top
> >
> >

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html