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

[Dimitry Andric]

On 29 Mar 2017, at 17:53, Brooks Davis <brooks at freebsd.org> wrote:
> 
> On Mon, Mar 27, 2017 at 03:25:04AM -0700, Mark Millard wrote:
...
>> This is extreme enough that next time I synchronize
>> /usr/ports and it has a devel/llvm40 update I'll
>> likely rebuild devel/llvm40 without using WITH_DEBUG= .
>> I'm more concerned with the time it takes than with
>> the file system space involved.
> 
> In the case of LLVM, enabling debug builds does a LOT more than adding
> symbols.  It's much more like enabling WITNESS and INVARIANTS in your
> kernel, except that the performance of the resulting binary is much
> worse than a WITNESS kernel (more like 10x slowdown).
> 
> As Dimitry points out, these builds are of questionable value in ports
> so garbage collecting the knob might be the sensable thing to do.

I suggest that for the LLVM ports, the DEBUG option should set the
RelWithDebInfo build type for CMake.  That will give you binaries which
can produce good backtraces, and a fair chance at debugging, in a pinch.

-Dimitry

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