FYI: what it takes for RAM+swap to build devel/llvm40 with 4 processors or cores and WITH__DEBUG= (powerpc64 example)

[Matthew Rezny]

On Thursday 30 March 2017 17:06:48 Alexey Dokuchaev wrote:
> On Mon, Mar 27, 2017 at 11:41:40AM +0200, Dimitry Andric wrote:
> > On 26 Mar 2017, at 23:36, Mark Millard <markmi at dsl-only.net> wrote:
> > > ...
> > > Also interesting was:
> > > 
> > > Installed packages to be REMOVED:
> > > 	llvm40-4.0.0.r4
> > > 
> > > Number of packages to be removed: 1
> > > 
> > > The operation will free 49 GiB.
> > 
> > Yes, this is big.  But there is no real need to build the llvm ports
> > with debug information, unless you want to hack on llvm itself.
> 
> Cc'ing jmd@ and rezny at .
> 
> I've been watching increasing size of our LLVM packages with increasing
> worry.  This is from my tinderbox cache:
> 
>   $ % env LANG=C ls -lh llvm3*
>   -rw-r--r--  1 root  wheel    17M Jan 29  2016 llvm35-3.5.2_1.txz
>   -rw-r--r--  1 root  wheel    18M Mar  7  2016 llvm36-3.6.2_2.txz
>   -rw-r--r--  1 root  wheel    27M Feb 28 01:05 llvm37-3.7.1_4.txz
>   -rw-r--r--  1 root  wheel   207M Jan 19 18:20 llvm38-3.8.1_5.txz
>   -rw-r--r--  1 root  wheel   244M Mar 23 16:42 llvm39-3.9.1_2.txz
> 
> Dimitry, do you know what had causes such a huge bump in 37 -> 38?
> 
> They take lots of time to build and package.  And given that llvm
> is indirect dependency of any X11-related port, it pessimises their
> build times as well (devel/libclc now requires devel/llvm40 after
> r437268).
> 
> With 49 GiB llvm40, I guess I won't be able to build-test post as my
> hardware would just not be capable enough.
> 
> ./danfe

LLVM 3.8 introduced the option to build a shared LLVM library, which is what 
Mesa needs for use at runtime (for e.g. compiling shaders), separate from 
linking to it. Previous versions only had one option, if the library was built 
then all the LLVM binaries were staticly linked to it.

LLVM devs state that static linking the LLVM binaries is only for developer 
use, users should not do that. Mesa's need was causing distributions to ship 
static linked LLVM binaries against that advice. So, they added a pair of 
switches so that we can separately control whether that library is built 
(required for Mesa) and used to link LLVM binaries (not desired).

llvm{35,36,37} are statically linked and thus smaller than normal. llvm38 
switched to dynamic linking, the default, thus the size grew. llvm39 added the 
library Mesa needs (we didn't turn on the option in llvm38 since Mesa jumped 
from 37 to 39), so it grew a little more. I assume llvm40 will be a bit 
bigger, but do not expect to see another jump as you've observed.