Re: [microblaze-uclinux] Preliminary 2.6.19 support for PetaLinux

[pfefferl@xxxxxxx (Dr. Johann Pfefferl)]

John Williams <jwilliams@xxxxxxxxxxxxxx> wrote:
> Hi Johann,
> 
> Thanks for the patches - some other comments below:
> 
> Dr. Johann Pfefferl wrote:
> 
> >- The kernel boots and a login is possible. See the attached boot log
> >  file. I provide a small bash script which converts an auto-config.in
> >  file to the new Kconfig.auto format. This way it is very easy to adapt
> >  the kernel to your platform.
> 
> I'll be releasing the updated MLD/TCL scripts soon enough, once they 
> stabilise a little.
> 
> >- I detected a slow down of the system performance during the boot
> >  phase.
> >  Until the boot message
> >  "io scheduler cfq registered (default)"
> >  the kernel seems to run with normal speed. But before/after the boot step
> >  "ttyS0 at MMIO 0xffff2000 (irq = 1) is a Xilinx OPB UART Lite"
> >  every action progresses less fast.
> 
> Yep - I've seen this too.  It's something to do with SYSFS - try turning 
> it off and see if you get any faster - I know I do.  Haven't looked into 
> why it's so slow yet.
> 

I have investigated this problem and found that it has to do with the
kernel configuration

Device Drivers  --->
  Character devices  --->
     Legacy (BSD) PTY support
     (256) Maximum number of legacy PTY in use (NEW)

If you reduce the number from 256 to 32 (for an embedded system this is
enough) the boot time is reduced by 5 seconds. Initialising the PTYs is
really slow. Perhaps there is also a relation between the sysfs and the ptys.
Moreover if I use only the unix98 ttys instead of the BSD ones the delay
also disappears. But after login, the system is still slow.

By the way there is a nice feature in the 2.6 kernel. printk can show a
timestamp. Enable it by

Kernel hacking  --->
   Show timing information on printks

Hans
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-- 
Dr. Johann Pfefferl   ---------------   mailto pfefferl at gmx dot net
==
 -o)   A computer program does what you tell it to do,
 /\\        not what you want it to do.               
_\_v-                                                 
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