CONFIG_NO_HZ causing poor console responsiveness

[Richard Cochran]

On Tue, Jun 29, 2010 at 02:54:17PM -0500, Timur Tabi wrote:
> I'm adding support for a new e500-based board (the P1022DS), and in
> the process I've discovered that enabling CONFIG_NO_HZ (Tickless
> System / Dynamic Ticks) causes significant responsiveness problems on
> the serial console.  When I type on the console, I see delays of up to
> a half-second for almost every character.  It acts as if there's a
> background process eating all the CPU.
> 
> I don't have time to debug this thoroughly at the moment.  The problem
> occurs in the latest kernel, but it appears not to occur in 2.6.32.
> 
> Has anyone else seen anything like this?

Yes, with a P2020RDB and kernel 2.6.35-rc1. Serial console is really
slow on an otherwise idle machine. I assumed it was a hardware
problem.

Richard