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Date:      Mon, 07 Oct 2024 09:00:58 +0000
From:      bugzilla-noreply@freebsd.org
To:        toolchain@FreeBSD.org
Subject:   [Bug 281765] llvm - ThinLTO never uses more than a single thread by default
Message-ID:  <bug-281765-29464-1lo0VDG0vB@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-281765-29464@https.bugs.freebsd.org/bugzilla/>
References:  <bug-281765-29464@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D281765

David Chisnall <theraven@FreeBSD.org> changed:

           What    |Removed                     |Added
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                 CC|                            |theraven@FreeBSD.org

--- Comment #3 from David Chisnall <theraven@FreeBSD.org> ---
(In reply to Dimitry Andric from comment #2)

> The reason for this was that lld was using way too many threads on many-c=
ore machines: nowadays just creating "hw.ncpu" threads is no longer a good =
default.

I don't believe this is true (unless RAM is not properly scaled with core
count).  The problem is build systems that try to parallelise link jobs.=20
Building LLVM with PARALLEL_LINK_JOBS=3D1, the upstream default remains the=
 right
one.  Building FreeBSD, it is not.=20=20

The fix for this in the bmake system is probably to wrap lld in a shell scr=
ipt
that acquires a lock, invokes lld, and then releases the lock and exits with
lld's exit code.

--=20
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