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

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Message-ID: <f170d7c2-2056-4f47-8847-af15b9a78b81@kernel.org>
Date: Mon, 26 Aug 2024 10:57:22 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Shung-Hsi Yu <shung-hsi.yu@...e.com>
Cc: 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 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).

> 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.

thanks,
-- 
js
suse labs