[syslinux] Measuring boot time

[Tal Lubko]

Hi Gene
Thanks for your reply.I'm trying to breakdown overall system boot time and to understand each component duration.
My linux image is a ~10 MB bzImage file with the rootfs cpio'ed inside.
I also have 2 BIOS images:- some general purpose BIOS
- a custom BIOS which loads real quick
I'm using TSC to measure time. I'm not sure it's the best way (I've read about CPU's synchronization problems with it) but I'm not sure how to do it otherwise.
I've added the following TSC reads at:1) the begining of a custom c32 module which later calls "syslinux_run_command"2) the begining of "start_kernel" function3) end of kernel load
As far as I understand the duration between 1 to 2 is bootloader time (am I wrong?).
Using the custom BIOS:- it takes ~1.1 seconds for bootloader to finish- it takes ~0.9 seconds for Linux to finish
Using the general purpose BIOS:- it takes ~0.45 seconds for bootloader to finish- it takes ~0.9 seconds for Linux to finish
Of course that the overall boot time with the general purpose BIOS is much longer than with the custom BIOS (the custom BIOS is intended to cut down boot time).
So I'm trying to understand:- Where does the extra bootloader time go when using the custom BIOS?- Is there a mechanisem built into syslinux code which can help solve this mystery?
Thanks again,Tal
 

     From: Gene Cumm <gene.cumm at gmail.com>
 To: Tal Lubko <tallubko at yahoo.com> 
Cc: "syslinux at zytor.com" <syslinux at zytor.com> 
 Sent: Wednesday, July 8, 2015 4:45 AM
 Subject: Re: [syslinux] Measuring boot time
   
On Mon, Jul 6, 2015 at 1:01 PM, Tal Lubko via Syslinux


<syslinux at zytor.com> wrote:
> Hello Everyone
> I'd like to know what's the best way to measure syslinux functions duration.I know how to measure overall time (from syslinux start), but is there an easy way to break it down?

What do you mean?  How long it takes to load individual files along
the way from initial start to the kernel handoff?  cptime.c32 might
offer a way to get some answers there.

Do you mean how long individual function calls take?  That sounds like
a non-trivial question if this is the case.

-- 
-Gene