Date: Thu, 30 Mar 2017 13:22:17 -0700 From: Mark Millard <markmi@dsl-only.net> To: Brooks Davis <brooks@freebsd.org>, Dimitry Andric <dim@FreeBSD.org> Cc: FreeBSD Ports <freebsd-ports@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org>, FreeBSD Toolchain <freebsd-toolchain@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: FYI: what it takes for RAM+swap to build devel/llvm40 with 4 processors or cores and WITH__DEBUG= (powerpc64 example) Message-ID: <F6F4B285-5D72-4B14-A12E-3D789AED063C@dsl-only.net> In-Reply-To: <20170329155316.GK59667@spindle.one-eyed-alien.net> References: <3EDEF0B7-59C5-4648-9737-6682E18645BC@dsl-only.net> <39C60316-F905-490D-B0AB-BC24D7F351A2@dsl-only.net> <7F94CE59-D2CC-4D6F-B1CD-FF3D1F8EDCE7@FreeBSD.org> <45E32F4F-A238-47AA-8E1E-7AD4D9E857D9@dsl-only.net> <20170329155316.GK59667@spindle.one-eyed-alien.net>
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On 2017-Mar-29, at 8:53 AM, Brooks Davis <brooks at freebsd.org> wrote: > On Mon, Mar 27, 2017 at 03:25:04AM -0700, Mark Millard wrote: >> On 2017-Mar-27, at 2:41 AM, Dimitry Andric <dim at FreeBSD.org> wrote: >> >>> On 26 Mar 2017, at 23:36, Mark Millard <markmi@dsl-only.net> wrote: >>>> >>>> I upgraded from llvm40 r4 to final. An interesting result was >>>> its creation of a backup package for llvm40-4.0.0.r4: >>>> >>>> about 13 cpu-core-hours running pkg create >>>> >>>> (Remember: I've been building with WITH_DEBUG= ) Its >>>> single-threaded status stands out via elapsed time >>>> approximately matching. >>>> >>>> I'll note that it was somewhat under 6 elapsed hours for >>>> staging to have been populated (-j4 with 4 cores present >>>> helps for this part). >>>> >>>> (Of course these elapsed-time figures are rather system >>>> dependent, although the ratio might be more stable.) >>>> >>>> >>>> >>>> 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. And >>> in that case, you are better served by a Subversion checkout or Git >>> clone from upstream instead. >>> >>> -Dimitry >> >> FYI: >> >> Historically unless something extreme like this ends up >> involved I build everything using WITH_DEBUG= or explicit >> -g's in order to have better information on any failure. >> >> 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. Sounds like the ALLOW_OPTIMIZATIONS_FOR_WITH_DEBUG technique would not change the "WITNESS and INVARIANTS"-like part of the issue. In fact if WITH_DEBUG= causes the cmake debug-style llvm40 build ALLOW_OPTIMIZATIONS_FOR_WITH_DEBUG might not make any difference: separate enforcing of lack of optimization. But just to see what results I've done "pkg delete llvm40" and am doing another build with ALLOW_OPTIMIZATIONS_FOR_WITH_DEBUG= and its supporting code in place in addition to using WITH_DEBUG= as the type of build fro FreeBSD's viewpoint. If you know that the test is a waste of machine cycles, you can let me know if you want. === Mark Millard markmi at dsl-only.net
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