Re: Any known way to build devel/llvm* ( such as devel/llvm19 ) with --threads=1 for its linker activity during the build?

On Aug 3, 2024, at 23:07, Mark Millard <marklmi@yahoo.com> wrote:

> 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:
> 
> LLVM ERROR: out of memory
> Allocation failed
> 
> (no system OOM activity or notices, so just a process size/fragmentation issue, or so I would expect).
> 
> On native armv7 I also had rust 1.79.0 fail that way so --but aarch64-as-armv7 built it okay.
> 
> I'm curious if --threads=1 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.)
> 
> 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.
> 
> 
> Native armv7 was a 2 GiByte OrangePi+ 2ed (4 cores) that had
> at boot time:
> 
> AVAIL_RAM+SWAP == 1958Mi+3685Mi == 5643Mi
> 
> and later had "Max(imum)Obs(erved)" figures:
> 
> Mem: . . .,
> 1728Mi MaxObsActive, 275192Ki MaxObsWired, 1952Mi MaxObs(Act+Wir+Lndry)
> 
> Swap: 3685Mi Total, . . .,
> 1535Mi MaxObsUsed, 3177Mi MaxObs(Act+Lndry+SwapUsed),
> 3398Mi MaxObs(A+Wir+L+SU), 3449Mi (A+W+L+SU+InAct)
> 
> 
> The aarch64-as-armv7 was a Win DevKit 2023 that has 8 cores and:
> 
> AVAIL_RAM+SWAP == 31311Mi+120831Mi == 152142Mi
> 
> So lots of 4 GiByte or smaller processes would fit.
> 

Absent finding a way to get --threads=1 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):

# 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 = hardware_concurrency(threads);
     config->thinLTOJobs = v;
+  } else if (sizeof(void*) <= 4) {
+    log("set maximum concurrency to 1, specify --threads= to change");
+    parallel::strategy = hardware_concurrency(1);
   } else if (parallel::strategy.compute_thread_count() > 16) {
     log("set maximum concurrency to 16, specify --threads= to change");
     parallel::strategy = hardware_concurrency(16);

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.

We will see if:

[00:00:33] [07] [00:00:00] Building   devel/llvm19@default | llvm19-19.1.0.r1

still fails to build as armv7 vs. if the change leads it to
manage to build as armv7.

===
Mark Millard
marklmi at yahoo.com