Hello!
I'm trying to optimize the startup time for an embedded system based on Atmel AT91RM9200.
I have done some tests to figure out the best configuration for the boot.bin, U-boot and the Linux kernel. All works fine.
Now I would
like to try starting my system with an uncompressed kernel image. My idea is that it takes some more time to uncompress a kernel than just boot a large one.
I have built one and installed it to the board. The problem is that nothing happens. The last displayed message comes from the boot loader U-boot.
"Ok
Starting the kernel..."

Are there special steps to do if one would like to run an uncompressed kernel image?
My kernel is Linux 2.6.17.

Greetings
Joakim Nordell

I'm not that sure. What's your transfer from DF? How long would it take to load compressed and uncompressed version? How long does the decompression take?

I'd count that before doing the non-trivial kernel work. My (good) guess is that bottleneck here would be DF reading, not decompression here.

The DF reading, before the message "Starting kernel..." is about 2 s with an uncompressed kernel and about 1 s with the compressed one.
The time to uncompress the bzImage is about 1.5 s. Therefore you are right. . . There isn't much time to save, about 5% in my case, but that's only true if the uncompressed kernel will start.
Do you have an idea about what's going wrong with the uncompressed one?

/Joakim Nordell

hi
r u using "mkimage" to compress the image
see the compressed image is less than uncompressed one
eg: if 4MB is ur uncompressed it will be around 1MB compressed

uboot will uncompress the image at bootup

Hello!
No, I'm just using mkimage to add the relevant U-boot information to the kernel image.
I have:
make Image
make zImage
and then ../u-boot/tools/mkimage for both Image and zImage.
In my case the zImage is about 850 kb and the uncompressed one is about 1580 kb. The size differens before and after mkimage is about 128 bytes.
The compressed one starts as you can expect. The uncompressed one stops at ones, without any error messages.
I have also tried the compress function within mkimage but the uncompress method within U-boot is slower than in the kernel so that's not the right way to save startup time.

Greetings
/Joakim Nordell

if ur getting any error like "bad magic number" there is problem with compression

if kernel is uncompressing at bootup and later got hanged it means ur static allocated drivers might have bugged ur kernel

r u seeing printk statements from drivers showing "device upgrade success"....

if drivers are all good
ur kernel not able to find ur ramdisk(ur rootfs)
(for me to uncompress & start the application it took 20seconds)