Re: CURRENT as gateway on not-so-fast hardware: where is a bottlneck?

On 08/14/2012 12:20 PM, Adrian Chadd wrote:
> Hi,
> 
> Would you be willing to compile a kernel with KTR so you can capture
> some KTR scheduler dumps?
> 
> That way the scheduler peeps can feed this into schedgraph.py (and you
> can too!) to figure out what's going on.
> 
> Maybe things aren't being scheduled correctly and the added latency is
> killing performance?

You might also try switching to SCHED_ULE to see if it helps.

Although, in the last few months as mav has been converging the 2 I've
started to see the same problems I saw on my desktop systems previously
re-appear even using ULE. For example, if I'm watching an AVI with VLC
and start doing anything that generates a lot of interrupts (like moving
large quantities of data from one disk to another) the video and sound
start to skip. Also, various other desktop features (like menus, window
switching, etc.) start to take measurable time to happen, sometimes
seconds.

... and lest you think this is just a desktop problem, I've seen the
same scenario on 8.x systems used as web servers. With ULE they were
frequently getting into peak load situations that created what I called
"mini thundering herd" problems where they could never quite get caught
up. Whereas switching to 4BSD the same servers got into high-load
situations less often, and they recovered on their own in minutes.

Doug