Dr. Lijun Luo wrote:
Dear all,
I need to configure/optimize a simple Linux kernel (either MontaVista or
open-source GIT kernel)
for DM6446 audio/video recorder on CF card. Has somebody done something
quite similar to speedup
bootup time? Which range we can get for the minimum? Is there better Linux
we can use? MobLinux?
PrKernel/PrOS?
See http://elinux.org/Boot_Time for lots of useful info on reducing
startup time. To do it right, you need to know your boot process
intimately - what you actually need to start and when.
I ended up ditching the /etc/rcN.d/ model, and just having a single
script to start all the required services. Here's an example:
- stripped down u-boot, no "press any key to interrupt" waiting
- get u-boot to copy the kernel directly from flash into memory,
bypassing any filesystem.
- boot stripped down kernel, preset lpj
- root fs is on a FS with short mount time (ubifs on NAND in this case)
Don't use JFFS2 if you care about a fast boot time.
Ideally, boot out of a read-only FS that doesn't need journal replay
and thus mounts instantly.
- mount other filesystems
- start udev (don't probe for devices on boot like udev normally does.
Instead, make sure all the device nodes that aren't hotpluggable are
already in the fs).
- load modules (cmem, dsplink, davinci_resizer, etc.)
- set hostname, ifup lo
- start app (user no longer cares what happens)
- start syslogd
- start udhcpc
- start ssh server
- start web server
The app is also designed to bring up a usable UI first, then the rest of
the stuff (like the DSP, etc) afterwards. With this, the UI comes up
within about 3 seconds from power on, and the system is ready to go
within about 4-5 seconds.
You could even move udev to after starting your app, so long as all the
device nodes you need to start up are in place.
As Phil said, there won't be a huge advantage between distros. I recall
MobiLinux advertises fast boot up time, you still won't get anywhere
near optimal unless you know precisely what you need.
HTH,
Bernard.
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