On Saturday 24 February 2001  3:23 pm, Reinoud Zandijk wrote:
> Dear all,
>
> In my efforts of compiling a GENERIC kernel to try out the new header file
> structure, I ran into a major slowdown....

Strange...

> The compiled GENERIC kernel was SOOO slow!!!! so much slower than my
> origional own configuration that i went to investigate it... the system
> time of running a `top' showed that the system time rose from about 1% or
> lower ro a staggering 5.6% or 6% (!) ... this really makes the system
> sluggish and its pretty bad :((
>
> The difference between my kernel (my own ismaelda) and the GENERIC kernel
> is basicly the removal of some devices and the switching off of `DDB' and
> `DIAGNOSTIC' ... to investigate the difference i'm now compiling my own
> config file with the extra option `DIAGNOSTIC'; I suspect that there is
> some very ``cheap'' check somewhere that really EATS processor time or
> trashes the TLB completely....

I've got a kernel running with DIAGNOSTIC and DDB, seems ok, however it's 
based on the RISCPC kernel.  Try building a profiled kernel. That'd help find 
where the kernel is spending lots of time.

> I suspect its the DDB for it gives the same wierd effects as seen on debug
> kernels (i.e. compiled with -g) since a debug kernel without DDB could be
> considered a bit silly.
>
> Have any of you seen this behaviour before? or have a clue as to where to
> find it ? I suspect its in the vidcconsole and/or pmap for i've seen some
> DIAGNOSTIC stuff there that might take this time too.

I've not noticed it, but then I've got an SA so perhaps wouldn't.

Cheers,
Chris