Spectris Arcom VIPER Quick Start Manual page 31

VIPER RedBoot and AEL Quickstart
Performance
To indicate the level of performance achieved using RTLinuxPro, Arcom prepared a test
application to exercise the Ethernet port with a ping flood and repeatedly write two large
files to the JFFS2 flash drive. Essentially, this represents a 'busy' foreground task
running under Linux. The jitter test was run with Arcom's standard Linux and then
repeated using RTLinuxPro. The test was performed on a standard VIPER board
running with a 400MHz CPU clock speed.
The worst-case jitter measurements running on a 400MHz PXA255 VIPER are shown
in the following table:
Linux variant
AEL
FSMLabs RTLinuxPro
Evaluating RTLinuxPro
The VIPER is not installed with RTLinuxPro as standard. The RTLinuxPro kernel and
RAM-based file system images are provided on the Development Kit CD in the folder
/images/rtlinux-demo. They can be booted using the following procedure. Doing so
does not affect the standard AEL image, which is stored in the Flash drive. To run the
test you must boot RTLinuxPro and then load the test application. To do this, follow
these steps:
1 Drop to the RedBoot command prompt. You do this by holding down Ctrl and
pressing C during the early stages of boot.
2 Enter the following commands:
RedBoot> load -r -b 0x800000 initrd.gz
RedBoot> load -r -b 0x400000 zImage.viper
RedBoot> exec -r 0x800000 -s 0x1000000 -c "console=ttyS0,115200
root=/dev/ram0"
The RTLinuxPro system boots and drops to a shell log in.
3 Mount the flash and copy multiple files repeatedly in and out of the file system:
# mount /dev/mtdblock3 /mnt
# while :; do cp /lib/libc-2.2.5.so /mnt/tmp/x; rm /mnt/tmp/x; done &
[1] 1722
# while :; do cp /lib/libc-2.2.5.so /mnt/tmp/y; rm /mnt/tmp/y; done &
[2] 1723
© 2005 Arcom Issue D
Real-time Linux on the VIPER
Maximum jitter
231ms
50.8µs
31