linux-kernel - Re: [PATCH 2/3] kbuild: handle module compression while running 'make modules

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Date:	Tue, 19 Aug 2014 20:54:02 +0200
From:	Bertrand Jacquin <beber@...eeweb.net>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, Willy Tarreau <w@....eu>
Subject: Re: [PATCH 2/3] kbuild: handle module compression while running
 'make modules_install'.

Hi,

D'ar meurzh 19 a viz Eost 2014 e 19 eur 55, « Rusty Russell » he deus skrivet :
> Andi Kleen <andi@...stfloor.org> writes:
> > Bertrand Jacquin <beber@...eeweb.net> writes:
> >>  
> >> +# CONFIG_MODULE_COMPRESS, if defined, will cause module to be compressed
> >> +# after they are installed in agreement with CONFIG_MODULE_COMPRESS_GZIP
> >> +# or CONFIG_MODULE_COMPRESS_XZ.
> >> +
> >> +mod_compress_cmd = true
> >> +ifdef CONFIG_MODULE_COMPRESS
> >> +  ifdef CONFIG_MODULE_COMPRESS_GZIP
> >> +    mod_compress_cmd = gzip -n -9
> >
> > Please don't use gzip -9. The gain is very small, but it can make
> > the time to compress much longer. Just use plain gzip.
> 
> Interesting:
> 
> $ time find * -name '*.ko' | xargs -n 1 gzip
> real	0m9.404s
> user	0m7.283s
> sys	0m1.667s
> $ du -c `find * -name '*.ko.gz'` | tail -n1
> 56412	total
> 
> time find * -name '*.ko' | xargs -n 1 gzip -9
> real	1m1.968s
> user	0m58.850s
> sys	0m1.786s
> $ du -c `find * -name '*.ko.gz'` | tail -n1
> 55764	total
> 
> $ time find * -name '*.ko' | xargs -n 1 xz
> real	1m23.396s
> user	1m13.893s
> sys	0m9.134s
> $ du -c `find * -name '*.ko.xz` | tail -n1
> 46868	total
> 
> $ time find * -name '*.ko' | xargs -n 1 xz -9
> real	1m47.202s
> user	1m25.962s
> sys	0m21.298s
> $ du -c `find * -name '*.ko.xz` | tail -n1
> 46868	total
> 
> So, Andi is right.  Please skip -9 for both options: it makes little
> (.gz) or no (.xz) difference and it slows things down.

Thank you Andi and Rusty for the feedback. I'm current updating patches
to drop -9 usage.

-- 
Beber
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