linux-kernel - Re: [RFC] kbuild: bpf: Do not run pahole with -j on 32bit userspace

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Message-ID: <CA+icZUWMxzAFtr8vsUUQ9OCR68K=F6d6MANx8HMTQntq494roA@mail.gmail.com>
Date: Mon, 26 Aug 2024 20:42:10 +0200
From: Sedat Dilek <sedat.dilek@...il.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Slaby <jirislaby@...nel.org>, Shung-Hsi Yu <shung-hsi.yu@...e.com>, dwarves@...r.kernel.org, 
	Jiri Olsa <olsajiri@...il.com>, masahiroy@...nel.org, linux-kernel@...r.kernel.org, 
	Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	linux-kbuild@...r.kernel.org, bpf@...r.kernel.org, msuchanek@...e.com
Subject: Re: [RFC] kbuild: bpf: Do not run pahole with -j on 32bit userspace

On Mon, Aug 26, 2024 at 7:03 PM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> On Mon, Aug 26, 2024 at 10:57:22AM +0200, Jiri Slaby wrote:
> > On 22. 08. 24, 17:24, Arnaldo Carvalho de Melo wrote:
> > > On Thu, Aug 22, 2024 at 11:55:05AM +0800, Shung-Hsi Yu wrote:
> > > I stumbled on this limitation as well when trying to build the kernel on
> > > a Libre Computer rk3399-pc board with only 4GiB of RAM, there I just
> > > created a swapfile and it managed to proceed, a bit slowly, but worked
> > > as well.
> >
> > Here, it hits the VM space limit (3 G).
>
> right, in my case it was on a 64-bit system, so just not enough memory,
> not address space.
>
> > > Please let me know if what is in the 'next' branch of:
>
> > > https://git.kernel.org/pub/scm/devel/pahole/pahole.git
>
> > > Works for you, that will be extra motivation to move it to the master
> > > branch and cut 1.28.
>
> > on 64bit (-j1):
> > * master: 3.706 GB
> > (* master + my changes: 3.559 GB)
> > * next: 3.157 GB
>
> > on 32bit:
> >  * master-j1: 2.445 GB
> >  * master-j16: 2.608 GB
> >  * master-j32: 2.811 GB
> >  * next-j1: 2.256 GB
> >  * next-j16: 2.401 GB
> >  * next-j32: 2.613 GB
> >
> > It's definitely better. So I think it could work now, if the thread count
> > was limited to 1 on 32bit. As building with -j10, -j20 randomly fails on
> > random machines (32bit processes only of course). Unlike -j1.
>
> Cool, I just merged a patch from Alan Maguire that should help with the
> parallel case, would be able to test it? It is in the 'next' branch:
>
> ⬢[acme@...lbox pahole]$ git log --oneline -5
> f37212d1611673a2 (HEAD -> master) pahole: Teduce memory usage by smarter deleting of CUs
>

*R*edzce? memory usage ...

-Sedat-

> Excerpt of the above:
>
>     This leads to deleting ~90 CUs during parallel vmlinux BTF generation
>     versus deleting just 1 prior to this change.
>
> c7ec9200caa7d485 btf_encoder: Add "distilled_base" BTF feature to split BTF generation
> bc4e6a9adfc72758 pahole: Sync with libbpf-1.5
> 5e3ed3ec2947c69f pahole: Do --lang_exclude CU filtering earlier
> c46455bb0379fa38 dwarf_loader: Allow filtering CUs early in loading
> ⬢[acme@...lbox pahole]$
>
> - Arnaldo
>