Date: Sun, 4 Aug 2024 23:15:45 -0700 From: Mark Millard <marklmi@yahoo.com> To: FreeBSD Toolchain <freebsd-toolchain@freebsd.org>, FreeBSD ARM List <freebsd-arm@freebsd.org> Subject: Re: Any known way to build devel/llvm* ( such as devel/llvm19 ) with --threads=1 for its linker activity during the build? Message-ID: <3D14B8AB-E8BF-497C-A84F-90F01A572FA5@yahoo.com> In-Reply-To: <82E78798-C376-45C4-80FE-96AD14229419@yahoo.com> References: <4FFD603F-E67C-4B62-B91B-8BE365EAA050@yahoo.com> <82E78798-C376-45C4-80FE-96AD14229419@yahoo.com>
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On Aug 4, 2024, at 14:31, Mark Millard <marklmi@yahoo.com> wrote:
> On Aug 3, 2024, at 23:07, Mark Millard <marklmi@yahoo.com> wrote:
>=20
>> My recent attempts to build devel/llvm18 and devel/llvm19 in an armv7 =
context (native or aarch64-as-armv7) have had /usr/bin/ld failures that =
stop the build and report as:
>>=20
>> LLVM ERROR: out of memory
>> Allocation failed
>>=20
>> (no system OOM activity or notices, so just a process =
size/fragmentation issue, or so I would expect).
>>=20
>> On native armv7 I also had rust 1.79.0 fail that way so --but =
aarch64-as-armv7 built it okay.
>>=20
>> I'm curious if --threads=3D1 use for the linker might allow the =
devel/llvm* builds to complete at this point. Similarly for rust. (top =
showed that the ld activity was multi-threaded.)
>>=20
>> Note: The structure of the poudriere-devel based native build =
attempts is historical and it used to work. Similarly for the =
aarch64-as-armv7 based build attempts. For now I'd just be exploring =
changes that might allow much of my historical overall structure to =
still work. But I expect that things are just growing to the point =
building is starting to be problematical with process address spaces =
that are bounded by a limit somewhat under 4 GiBytes.
>>=20
>>=20
>> Native armv7 was a 2 GiByte OrangePi+ 2ed (4 cores) that had
>> at boot time:
>>=20
>> AVAIL_RAM+SWAP =3D=3D 1958Mi+3685Mi =3D=3D 5643Mi
>>=20
>> and later had "Max(imum)Obs(erved)" figures:
>>=20
>> Mem: . . .,
>> 1728Mi MaxObsActive, 275192Ki MaxObsWired, 1952Mi =
MaxObs(Act+Wir+Lndry)
>>=20
>> Swap: 3685Mi Total, . . .,
>> 1535Mi MaxObsUsed, 3177Mi MaxObs(Act+Lndry+SwapUsed),
>> 3398Mi MaxObs(A+Wir+L+SU), 3449Mi (A+W+L+SU+InAct)
>>=20
>>=20
>> The aarch64-as-armv7 was a Win DevKit 2023 that has 8 cores and:
>>=20
>> AVAIL_RAM+SWAP =3D=3D 31311Mi+120831Mi =3D=3D 152142Mi
>>=20
>> So lots of 4 GiByte or smaller processes would fit.
>>=20
>=20
> Absent finding a way to get --threads=3D1 to be what is used, I
> made the following crude way to test, built it, installed it
> in the armv7 directory tree used for aarch64-as-armv7, and
> then started an aarch64-as-armv7 test of building devel/llvm19
> to see what the consequences are (leading whitespace details
> might not be preserved):
>=20
> # git -C /usr/main-src/ diff contrib/llvm-project/
> diff --git a/contrib/llvm-project/lld/ELF/Driver.cpp =
b/contrib/llvm-project/lld/ELF/Driver.cpp
> index 8b2c32b15348..299daf7dd6fa 100644
> --- a/contrib/llvm-project/lld/ELF/Driver.cpp
> +++ b/contrib/llvm-project/lld/ELF/Driver.cpp
> @@ -1587,6 +1587,9 @@ static void readConfigs(opt::InputArgList &args) =
{
> arg->getValue() + "'");
> parallel::strategy =3D hardware_concurrency(threads);
> config->thinLTOJobs =3D v;
> + } else if (sizeof(void*) <=3D 4) {
> + log("set maximum concurrency to 1, specify --threads=3D to =
change");
> + parallel::strategy =3D hardware_concurrency(1);
> } else if (parallel::strategy.compute_thread_count() > 16) {
> log("set maximum concurrency to 16, specify --threads=3D to =
change");
> parallel::strategy =3D hardware_concurrency(16);
>=20
> Basically, if the process address space has to be "small", avoid
> any default memory use tradeoffs that multi-threading the linker
> might involve --even if that means taking more time.
>=20
> We will see if:
>=20
> [00:00:33] [07] [00:00:00] Building devel/llvm19@default | =
llvm19-19.1.0.r1
>=20
> still fails to build as armv7 vs. if the change leads it to
> manage to build as armv7.
The link attempt for "-o bin/llvm-exegesis" still failed:
LLVM ERROR: out of memory
Allocation failed
A potentially interesting note is that:
https://llvm.org/docs/CommandGuide/llvm-exegesis.html
reports:
QUOTE
llvm-exegesis currently only supports X86 (64-bit only), ARM (AArch64 =
only), MIPS, and PowerPC (PowerPC64LE only) on Linux for benchmarking. =
Not all benchmarking functionality is guaranteed to work on every =
platform. llvm-exegesis also has a separate analysis mode that is =
supported on every platform that LLVM is.
END QUOTE
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
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