[blfs-dev] Resources for qtwebengine

Ken Moffat zarniwhoop at ntlworld.com
Wed Dec 13 09:08:51 PST 2017


On Wed, Dec 13, 2017 at 10:07:07AM -0600, Bruce Dubbs wrote:
> Thomas Trepl wrote:
> > Am 2017-12-13 13:39, schrieb Thomas Trepl:
> > > hi all,
> > > 
> > > I'm currently trying to compile version 5.10 but it seems my machine
> > > is too small. It is a VBox-VM with 2GB RAM, 2GB swap partition but
> > > compilation failed with "virtual memory exhausted". I increased the
> > > mem to 3 GB but it looks like the process runs in same situation
> > > (currently at 13957/21739 targets to compile).
> > > 

I think such a small system will have pains with several large
desktop packages.  I haven't built in a VM in ages, but on my i3
(4GB RAM, 3.75GB available) and my A10 Kaveri (8GB RAM but < 7GB
available) building qtwebengine is unpleasant.

How do the 4 CPUs compare to what your host system offers ?  My
impression has always been that *qemu* will not map CPUs 1:1 (there
is an overhead of running a VM) and for a big package that DOES make
a difference.  But I have no idea about vmware.

Also: qtwebengine, at least until 5.9, has used its included ninja
if there is no system version.  And ninja spawns N+2 jobs if more
than 2 CPUs.  For system ninja we have Bruce's patch to use an ENVVAR
to limit the number of jobs.  Limiting the number of jobs might help
in a VM or anywhere else short of memory - these are not trivial
'build some little C file' jobs, these are "throw a kitchen-sink of
headers at this complex C++ code" jobs.

If you only have 4 (real) cores, using -j6 on large C++ files is
unlikely to help - it might hinder, it might not make a lot of
difference.

For a clean build, ninja has few benefits.  In cmake packages it is
marginally faster than the Makefiles cmake produces, but only a
little.  The benefit is for developers who (re) build in a dirty
tree after making a minor change.  In that situation Makefiles
created by cmake can do a lot of work, good Makefiles from
autotools, and ninja files, will just check what needs to be
rebuilt.

ĸen
-- 
Truth, in front of her huge walk-in wardrobe, selected black leather
boots with stiletto heels for such a barefaced truth.
                                     - Unseen Academicals


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