Arch Linux

beta990

Member

Registered: 2011-07-10

Posts: 207

Compiling kernels take a lot of time

I have the following PC specs:
- Intel Core i5-2400 @ 2.4Ghz (no overclock)
- 8GB DDR3 1333Mhz
- ASUS P8H67-M Pro
- Samsung 840 SSD (building on /home)

Building a kernel (without unused/unneeded modules) takes more than 40 mins.
Even when using ccache, the compile speeds don't improve (at all).
The ~/.ccache folder is used (since it get's bigger every time after compiling), but don't know if it my PC or a configuration error.
Also tweaking /etc/makepkg.conf as stated in the .config didn't improved anything.

What build speeds should I expect with these specs.?
I have read reports from users that have build speeds of 7 mins. (but using different hardware configuration).

Thanks

Last edited by beta990 (2015-08-02 16:13:17)

Trilby

Inspector Parrot

Registered: 2011-11-29

Posts: 30,480

Website

Re: Compiling kernels take a lot of time

40 minutes is a long time?!

The last time I build a kernel it ran for 8 hours.  Admittedly on lower spec hardware, but still.  It's a kernel - it will take a while.

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"UNIX is simple and coherent" - Dennis Ritchie; "GNU's Not Unix" - Richard Stallman

dockland

Member

From: Sweden

Registered: 2015-06-06

Posts: 861

Re: Compiling kernels take a lot of time

I have the following PC specs:
- Intel Core i5-2400 @ 2.4Ghz (no overclock)
- 8GB DDR3 1333Mhz
- ASUS P8H67-M Pro
- Samsung 840 SSD (building on /home)

Building a kernel (without unused/unneeded modules) takes more than 40 mins.
Even when using ccache, the compile speeds don't improve (at all).
The ~/.ccache folder is used (since it get's bigger every time after compiling), but don't know if it my PC or a configuration error.
Also tweaking /etc/makepkg.conf as stated in the .config didn't improved anything.

What build speeds should I expect with these specs.?
I have read reports from users that have build speeds of 7 mins. (but using different hardware configuration).

Thanks

I use tmpfs. On my i7 4790K @ 4.4 GHz it takes about 10-15 minutes.

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graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,732

Website

Re: Compiling kernels take a lot of time

+1 for tmpfs but that really won't affect speed.

Try modprobed-db from the AUR and only build the modules you need.  You will do this from a `make localmodconfig` in the kernel PKGBUILD.  See linux-ck's PKGBUILD for an example.  Doing this makes a significant difference.  Also see the wiki page for example build times.

Last edited by graysky (2015-08-02 17:19:17)

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AUR packages • Zsh and other configs

sekret

Member

Registered: 2013-07-22

Posts: 308

Re: Compiling kernels take a lot of time

Use

make localmodconfig

This will speed things up, because then it only builds modules your system uses right now.
edit: Or did you mean this by "without unused/unneeded modules"?

Last edited by sekret (2015-08-02 16:59:30)

beta990

Member

Registered: 2011-07-10

Posts: 207

Re: Compiling kernels take a lot of time

Use

make localmodconfig

This will speed things up, because then it only builds modules your system uses right now.
edit: Or did you mean this by "without unused/unneeded modules"?

Yep

It should compile around the 120~ modules.

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: Compiling kernels take a lot of time

I have read reports from users that have build speeds of 7 mins

My custom kernel compiles in under 5 minutes. But it's stripped down, with unneeded modules removed.

At the other end of the scale - libreoffice 5 compiles in 118 minutes (i.e. 2 hours).

40 minutes for your *entire kernel* sounds about right.

beta990

Member

Registered: 2011-07-10

Posts: 207

Re: Compiling kernels take a lot of time

+1 for tmpfs but that really won't affect speed.

Try modprobed-db from the AUR and only build the modules you need.  You will do this from a `make localmodconfig` in the kernel PKGBUILD.  See linux-ck's PKGBUILD for an example.  Doing this makes a significant difference.  Also see the wiki page for example build times.

I'm already running this on all my machines, will check if I can strip even more.

I have read reports from users that have build speeds of 7 mins

My custom kernel compiles in under 5 minutes. But it's stripped down, with unneeded modules removed.

At the other end of the scale - libreoffice 5 compiles in 118 minutes (i.e. 2 hours).

40 minutes for your *entire kernel* sounds about right.

This sounds like you unset a lot of modules, also for print/*net support.
Aren't you missing anything? e.g. when trying new apps and/or hardware?

Weird that the kernel builds faster than Libreoffice, think the compiler makes a huge differences.

I use tmpfs. On my i7 4790K @ 4.4 GHz it takes about 10-15 minutes.

Will try tmpfs instead of my SSD. Thought the SSD would be fast enough.

40 minutes is a long time?!

The last time I build a kernel it ran for 8 hours.  Admittedly on lower spec hardware, but still.  It's a kernel - it will take a while.

16 hours compiling on rPi.

I'm compiling the kernels on my i5 and then install them on the target PC.
But still I would like to have some improvements in building the kernel.

graysky

Wiki Maintainer

From: :wq

Registered: 2008-12-01

Posts: 10,732

Website

Re: Compiling kernels take a lot of time

Do not compile in RPi without distcc.

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AUR packages • Zsh and other configs

beta990

Member

Registered: 2011-07-10

Posts: 207

Re: Compiling kernels take a lot of time

Do not compile in RPi without distcc.

But is it not limited by the Fa-port?
I still think compiling on the main and/or virtual machine (ARM) is faster than distcc.

Or I'm completely wrong?

Last edited by beta990 (2015-08-02 18:08:04)

clfarron4

Member

From: London, UK

Registered: 2013-06-28

Posts: 2,175

Website

Re: Compiling kernels take a lot of time

My i3-2370M processor builds the generic kernels I maintain in 45 minutes, using the -j4 flag in /etc/makepkg.conf, going up to about 1h 20mins if I use -j1.

To me, it does sound like you're still building quite a generic kernel though. Stripping down with the tools suggested should cut down the build time quite a bit.

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beta990

Member

Registered: 2011-07-10

Posts: 207

Re: Compiling kernels take a lot of time

My i3-2370M processor builds the generic kernels I maintain in 45 minutes, using the -j4 flag in /etc/makepkg.conf, going up to about 1h 20mins if I use -j1.

To me, it does sound like you're still building quite a generic kernel though. Stripping down with the tools suggested should cut down the build time quite a bit.

Thanks for the suggestion, will try if it improves building the next kernel.

So far going to test with ccache + tmpfs and the -j4 flag.

dockland

Member

From: Sweden

Registered: 2015-06-06

Posts: 861

Re: Compiling kernels take a lot of time

My i3-2370M processor builds the generic kernels I maintain in 45 minutes, using the -j4 flag in /etc/makepkg.conf, going up to about 1h 20mins if I use -j1.

To me, it does sound like you're still building quite a generic kernel though. Stripping down with the tools suggested should cut down the build time quite a bit.

Thanks for the suggestion, will try if it improves building the next kernel.

So far going to test with ccache + tmpfs and the -j4 flag.

-j4 flag will do "wonders"
I run my 4790K with HT with ="-j9"
Works like charm, as stated.

---

I possess a device, in my pocket, that is capable of accessing the entirety of information known to man.
I use it to look at funny pictures of cats and to argue with strangers.

beta990

Member

Registered: 2011-07-10

Posts: 207

Re: Compiling kernels take a lot of time

Thanks guys for all the tips.

Results:
- Build time has been reduced to max. 30/20 mins. for my desktop and Intel i3 NAS (tmpfs)
- Build time for my NAS has been reduced with only one hour (a simple dual-core 1Ghz AMD fusion!)

By disabling unneeded modules (modprobed-db), using ccache, adding -j2/4 to make flags, .. I'm happy with the new changes.