linux-kernel - Re: [GIT PULL] Update LZO compression

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Date:	Thu, 16 Aug 2012 20:18:57 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Roman Mamedov <rm@...anrm.ru>, Johannes Stezenbach <js@...21.net>,
	"Markus F.X.J. Oberhumer" <markus@...rhumer.com>,
	linux-kernel@...r.kernel.org, chris.mason@...ionio.com,
	linux-btrfs@...r.kernel.org, Nitin Gupta <ngupta@...are.org>,
	Richard Purdie <rpurdie@...nedhand.com>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [GIT PULL] Update LZO compression

On Thu, Aug 16, 2012 at 7:52 PM, Andi Kleen <andi@...stfloor.org> wrote:
>> I have locked the Allwinner A10 CPU in my Mele A2000 to 60 MHz using cpufreq-set,
>> and ran your test. rnd.lzo is a 9 MB file from /dev/urandom compressed with lzo.
>> There doesn't seem to be a significant difference between all three variants.
>
> I found that in compression benchmarks it depends a lot on the data
> compressed.
>
> urandom (which should be essentially incompressible) will be handled
> by different code paths in the compressor than other more compressible data.
> It becomes a complicated memcpy then.

In addition, locking the CPU to 60 MHz may improve the memory access penalty,
as a cache miss may cost much less cycles.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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