linux-kernel - Re: [kernel.org users] XZ Migration discussion

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Date:	Sat, 13 Feb 2010 19:49:17 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	Pavel Machek <pavel@....cz>, "J.H." <warthog9@...nel.org>,
	"FTPAdmin Kernel.org" <ftpadmin@...nel.org>, users@...nel.org,
	lasse.collin@...aani.org,
	linux-kernel <linux-kernel@...r.kernel.org>, mirrors@...nel.org
Subject: Re: [kernel.org users] XZ Migration discussion

On Sat, Feb 13, 2010 at 18:10, Jean Delvare <khali@...ux-fr.org> wrote:
> On Thu, 11 Feb 2010 21:51:29 +0100, Pavel Machek wrote:
>> I believe this is cleanest. gzip has performance advantages, (...)
>
> I have been investigating this issue and would like to share my
> findings as an additional data point for this discussion.
>
> For my testing, I have been using the slowest machine I still have
> available here: a Pentium 166 MMX, with 64 MB of memory and a slow hard
> disk drive. I've been writing down the duration of each task it took to
> boot kernel 2.6.27.45 on this machine. I did this for both .gz and .bz2
> formats.
>
> Raw results are as follow (format=min:s):
>
> downloading linux-2.6.27.tar.bz2          5:01
> downloading patch-2.6.27.45.bz2           0:02
> unpacking linux-2.6.27.tar.bz2            7:28
> applying patch-2.6.27.45.bz2              1:21
> ----------------------------------------------
> total for bz2                            13:52
>
> downloading linux-2.6.27.tar.gz           6:23
> downloading patch-2.6.27.45.gz            0:02
> unpacking linux-2.6.27.tar.gz             3:20
> applying patch-2.6.27.45.gz               1:10
> ----------------------------------------------
> total for gz                             10:55
>
> So the gz option is unsurprisingly faster, setting up the source tree
> takes almost 3 minutes less (-21%).
>
> Then the (common) build and installation times:
>
> building                                117:26
> installing modules                        0:12
> ----------------------------------------------
> total                                   117:38
>
> This is a customized kernel, as small as I could do, with almost no
> features and the minimal set of drivers. As you can see, the build time
> is one order of magnitude greater than the tree setup time. Comparing
> the total times from download to install between bz2 and gz:
>
> bz2: 13:52 + 117:38 = 131:30
> gz:  10:55 + 117:38 = 128:33
>
> Compared to bz2, gz saves... 2% on the overall time. As a conclusion, I
> think we can plain discard the argument "I need .gz because my machine
> is slow" from now on. It simply doesn't hold.

166 MHz and 64 MB of RAM is still an order of magnitude more than some other
machines Linux is capable of running on.

Of course we no longer build kernels on those machines natively, we
cross-compile
on much faster machines (and use git to fetch the kernel sources, FWIW ;-).

BTW, who still downloads full kernel tarballs? From my experience, that's mostly
distro people who have scripts to build kernels from tarballs + a
bunch of patches?
I guess actual developers use git nowadays, even if they're stuck on
an old 2.6.x kernel?
Backporting critical fixes is sooo much easier using git cherry-pick...

Do we have statistics about tarball downloads vs. git clone / git pull?

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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