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

[Mark Millard]

Summary: RAM+(peak swap) was about 26 GiBytes.
         Also: about 118 GiByte /usr/obj/. . ./llvm40/ area.
         (2 processors, 2 cores each, all in use;
          WITH_DEBUG= used)

The peak usage times were when the 4 cores were
each busy running ld at the same time.

[So far as I know FreeBSD does not report peak swap usage
"since boot". So I do not have a cross check on if I missed
seeing a higher peak then I report in the details below.]

What all this note spans as part of the build:

# more /var/db/ports/devel_llvm40/options
# This file is auto-generated by 'make config'.
# Options for llvm40-4.0.0.r4
_OPTIONS_READ=llvm40-4.0.0.r4
_FILE_COMPLETE_OPTIONS_LIST=CLANG DOCS EXTRAS LIT LLD LLDB
OPTIONS_FILE_SET+=CLANG
OPTIONS_FILE_SET+=DOCS
OPTIONS_FILE_SET+=EXTRAS
OPTIONS_FILE_SET+=LIT
OPTIONS_FILE_SET+=LLD
OPTIONS_FILE_SET+=LLDB

The system clang 4.0 was used to do the build. A port
binutils was used (-B${LOCALBASE}/bin/ in CFLAGS,
CXXFLAGS, an CPPFLAGS). The kernel was non-debug generally
but buildworld buildkernel did not have MALLOC_PRODUCTION= .
The llvm40 build did have MALLOC_PRODUCTION= .

# uname -paKU
FreeBSD FBSDG5L 12.0-CURRENT FreeBSD 12.0-CURRENT  r314687M  powerpc powerpc64 1200023 1200023

Most of what I have access to for FreeBSD does not have a
big enough configuration to do a WITH_DEBUG= build of llvm40
on a machine with 4 cores, all in use.

One type of environment that does is an old PowerMac G5
so-called "Quad Core" that has 16 GiBytes of RAM, 17 GiBytes
of swap, and a 480 GiByte SSD (but extra over provisioned so
it appears even smaller for the file system+swap).

Watching with top the peak swap usage that I saw was
56% of the 17 GiByte --so call it 10 GiBytes or so.

So something like 16 GiBytes RAM + 10 GiBytes swap
and so something like 26 GiByte total.

I used portmaster with -DK. Afterwards the /usr/obj/
sub-area for llvm40 used totaled to a size of:

# du -sg /usr/obj/portswork/usr/ports/devel/llvm40
118	/usr/obj/portswork/usr/ports/devel/llvm40

So around 118 GiBytes of disk space.

Showing the major space usage contributions:

# du -sg /usr/obj/portswork/usr/ports/devel/llvm40/work/.build/* /usr/obj/portswork/usr/ports/devel/llvm40/work/stage/usr/local/llvm40/*
. . .
29	/usr/obj/portswork/usr/ports/devel/llvm40/work/.build/bin
. . .
29	/usr/obj/portswork/usr/ports/devel/llvm40/work/.build/lib
. . .
12	/usr/obj/portswork/usr/ports/devel/llvm40/work/.build/tools
. . .
26	/usr/obj/portswork/usr/ports/devel/llvm40/work/stage/usr/local/llvm40/bin
. . .
24	/usr/obj/portswork/usr/ports/devel/llvm40/work/stage/usr/local/llvm40/lib
. . .



Side notes that are more system specific:

The timestamps on the script output file indicate that
the build took about 8 hours 24 minutes.

The powerpc64 system used was built with the system clang
4.0 compiler and a port-based binutils. This is despite that
clang 4.0 produces code that has any thrown C++ exceptions
completely non-functional for powerpc64 (program crashes
via signals reporting problems).

===
Mark Millard
markmi at dsl-only.net