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Old 05-23-2006, 09:30 AM   #1
Registered: Feb 2006
Distribution: Slackware 10.2, (, FC 5
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Question regarding kernel size difference between 2.4.x and 2.6.x

As I mentioned in another thread, I did my first kernel compile recently. I used the source for and all went well b/c of the excellent documentation I had.

The 2.4 kernel in my 10.2 Slack install is about 1.4MB. When I upgraded to the generic 2.6.13 from disc 2, that one was about 1.6MB or so. Finally, my custom compiled kernel using the source is right at about 1.95MB.

I googled the topic and found info that said the 2.6 kernel increased the size by 10 to 30%. The one I compiled seems to boot faster, and it seems to be just as fast during normal operation.

I'm just wondering if that kind of kernel size increase is what everyone here is typically seeing with 2.6.
Old 05-23-2006, 10:56 AM   #2
Registered: Oct 2003
Location: Kuala Lumpur, Malaysia
Distribution: Slackware 13.37 current
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The kernel size is not so critical these days when an entry level pc has 256MB of ram.

Even generic could easily be cut down by dropping the unused ide controllers.

2.6 will be some 20% bigger than 2.4 as it has a much larger pool of supported hardware and a lot more complex code managing memory, processes and locking.
Old 05-28-2006, 05:31 PM   #3
Bruce Hill
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Registered: Jun 2003
Location: McCalla, AL
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I find that my custom kernels are sometimes smaller than the default Slackware kernels:

My workstation, where I have it trimmed to the bone:
mingdao@silas:~$ ls -lh /boot/
-rw-r--r-- 1 root root 1.2M 2006-03-24 08:07 vmlinuz-2.6.16
-rw-r--r-- 1 root root 1.2M 2006-05-08 07:29 vmlinuz-
-rw-r--r-- 1 root root 1.2M 2006-05-22 19:32 vmlinuz-
-rw-r--r-- 1 root root 1.2M 2006-05-24 08:35 vmlinuz-
-rw-r--r-- 1 root root 1.2M 2006-04-10 15:02 vmlinuz-
-rw-r--r-- 1 root root 1.3M 2006-03-13 09:49 vmlinuz-ide-2.4.32
My wife's PC, which is fully functional, but not so trimmed:
anna@peter:~$ ls -lh /boot
-rw-r--r-- 1 root root 1.4M 2006-05-22 18:51 vmlinuz-
-rw-r--r-- 1 root root 1.4M 2006-04-23 21:04 vmlinuz-
-rw-r--r-- 1 root root 1.3M 2006-03-13 09:49 vmlinuz-ide-2.4.32
My laptop, road-ready for many obstacles:
mingdao@titus:~$ ls -lh /boot/
-rw-r--r-- 1 root root 1.2M 2006-02-18 13:21 vmlinuz-
-rw-r--r-- 1 root root 1.2M 2006-03-26 14:16 vmlinuz-2.6.16
-rw-r--r-- 1 root root 1.2M 2006-05-22 19:15 vmlinuz-
-rw-r--r-- 1 root root 1.2M 2006-05-24 09:07 vmlinuz-
-rw-r--r-- 1 root root 1.3M 2006-03-13 09:49 vmlinuz-ide-2.4.32
On a customer's PC, with hardware new to me:
dave@matthews:~$ ls -lh /boot/
-rw-r--r-- 1 root root 1.3M 2006-05-15 18:37 vmlinuz-
-rw-r--r-- 1 root root 1.3M 2006-05-22 10:47 vmlinuz-
-rw-r--r-- 1 root root 1.3M 2006-03-13 09:49 vmlinuz-ide-2.4.32
The 2.6 kernels compile faster, boot faster, and run faster.
Old 05-28-2006, 07:01 PM   #4
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Originally Posted by Chinaman
I find that my custom kernels are sometimes smaller than the default Slackware kernels
Mine always are.

I guess Pat tries to build kernels which will work on the widest possible selection of hardware.

In the 2.4 days, I could compile a custom kernel half the size of Pat's. The last 2.4 kernel I ran (2.4.21) was approximately 700Kb.

With 2.6 I can't get them smaller than 1.1M. I haven't done as much experimenting with 2.6 as I did with 2.4, so there may be something I'm missing.
Originally Posted by Chinaman
The 2.6 kernels compile faster, boot faster, and run faster.
You're not wrong. In my experience to date, 2.6 is superior to 2.4 in everything except module handling. For example: To get module unloading with 2.6, you need to choose an option which makes the kernel larger and more complex. Also, there are certain modules which won't auto-load the way they did under 2.4. I don't know why. Other than that, 2.6 is stable, fast & feature packed.

Last edited by rkelsen; 05-28-2006 at 07:09 PM.
Old 05-28-2006, 07:33 PM   #5
Registered: May 2004
Location: South Carolina
Distribution: Slackware 11.0
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Size doesn't matter. At all.

Any PC made after 1993 or so would be able to support any linux kernel, even with practically everything (within reason) built in with no performance hit.

You'll see probably no speed increase at all with a smaller kernel unless you are on very ancient hardware.

In other words, if your PC is fast enough to compile a kernel within 3 days of time, you won't notice anything from a smaller kernel, and if it does take you more than 3 days to compile a kernel, you probably wouldn't find it worth it to do it anyway.

(although changing the kernel options back to more 'sane' defaults, such as 1000hz, preemption, and optimizing for your processor make a HUGE performance difference, but the kernel will be bigger too, but it won't make any real difference.)


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