Re: Linux Kernel speculation
- From: AZ Nomad <aznomad.3@xxxxxxxxxxxxxxxxxxx>
- Date: Thu, 21 May 2009 13:24:42 -0500
On Thu, 21 May 2009 12:36:38 -0500, Nobby Anderson <nobby@xxxxxxxxxxxxxxx> wrote:
We have a number of systems based on the ppc core in a Virtex 4 FX12. The
system has 4MB flash RAM for program storage and 32MB RAM and uses one of
the EDK-supplied Ethernet cores for comms (temac).
Some time ago I ported a 2.6.15 kernel onto it and we've been running with
that ever since. The system boots with a small bootloader which loads uboot
which in turn loads the Linux kernel. The kernel has an initrd and boots
into a ram filesystem that's loaded off a compressed image on the flash.
The total boot time is of the order of 35 seconds - that's from a cold start
to the application running with tcp sockets open to receive stuff from the
LAN. I'd like to explore ways of making that faster.
It seems that the biggest pauses in the boot process are to do with the
initrd loading, then the flash RAM being decompressed into RAM for the
ramdisk, and then there's a long pause while the Etherent hardware
initialises. There's also about 5 seconds lost at the start while the
system looks for keypresses to activate the two boot loaders' flash-ram
loading tools, and I'm going to replace both of those to look for a
jumper setting on the board.
What's the most effective route to further reducing the boot time? For
example, is there anything I can do to get rid of the initrd, or to
speed up loading a flash disk into RAM? Is there any benefit to going
for a later kernel - later desktop kernels seems to bood a lot faster
than older ones on the same hardware, but I'm unsure how much of that
is to do with more efficient driver and other module loading and
how muchg is to do with the basic kernel itself. I've already removed
everything from the kernel that's not needed and everything that it needs
is compiled in, I believe.
Do you have unnecessary devices compiled in your kernel or as modules
in your initrd?
I have a diskless multimedia computer that boots off a LAN and it
takes <25 seconds to boot to a gui application. Without the gui, it
would be <20 seconds, for example the ssh server is available in 15
seconds from bios start.
.
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