linux-kernel - Re: [PROBLEM] Very long .deb package build times for bindeb-pkg build target

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Date: Thu, 11 Jan 2024 16:37:28 +0100
From: Nicolas Schier <nicolas@...sle.eu>
To: Mirsad Todorovac <mirsad.todorovac@....hr>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PROBLEM] Very long .deb package build times for bindeb-pkg
 build target

Hi Mirsad,

On Thu 11 Jan 2024 13:22:39 GMT, Mirsad Todorovac wrote:
> Hi,
> 
> With this new release, it seems that Debian kernel build uses "xz" in single-
> threaded mode:
> 
> Tasks: 484 total,   2 running, 481 sleeping,   0 stopped,   1 zombie
> %Cpu(s):  2.5 us,  2.2 sy,  6.3 ni, 85.1 id,  2.3 wa,  0.0 hi,  1.7 si,  0.0 st
> MiB Mem :  64128.3 total,    524.3 free,   5832.0 used,  58540.9 buff/cache
> MiB Swap:  32760.0 total,  32758.7 free,      1.2 used.  58296.3 avail Mem
> 
>     PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+
> COMMAND
> 
>  978084 marvin    30  10  112440  97792   2432 R 100.0   0.1  29:30.23 xz
> 
> 
> Before dpkg-deb was using up to 3200% of CPU time on a 16 core SMT CPU.
> 
> Can it be something with dpkg-deb --thread-max=%n option?

I cannot find any --thread-max option in Linux tree.  Do you call 
dpkg-deb manually or somehow induce a thread maximum?

> Waiting for half an hour just for the build of linux-image-...-dbg package
> seems like an overkill ...

With current v6.7 release tree I do not see the reported slow-downs 
when building bindeb-pkg; I tested by cross-compiling for arm64 on 
amd64 with CONFIG_MODULE_COMPRESS_XZ=y and =n).

Both take roughly 5mins on my 24-core i9 system.

Kind regards,
Nicolas

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