Re: loading pages to memory causes high latency

[Stanislav Meduna <stano@meduna.org>]

On 27.10.2012 10:38, Thomas Gleixner wrote:

> There is not much we can do about that unless we want to do a major
> surgery on that pata driver code.
> 
> So either you disable the throttler or you reconfigure the pata irq
> thread to SCHED_OTHER, which will slow it down a bit, but avoids the
> hogging of the machine with a RT task going wild.

Thank you for the analysis. Yep I'll reconfigure it to SCHED_OTHER -
file access is a totally low-prio thing in my application and I was more
afraid of a possibility where someone fetching logfiles or something
like that will bring the application to the knees.

BTW what granularity does the throttler have? I cannot live with
50 ms lag once in a second, but in my case I can well live with
5 ms lag once in 100 ms (even if that means that the throttler
would be activated more often).

Right now I have

CONFIG_TICK_ONESHOT=y
CONFIG_NO_HZ=y
CONFIG_HZ=1000
CONFIG_SCHED_HRTICK=y

and lacking better choices my clock source is TSC. I admit that
I do not know what precisely each setting does - the NO_HZ combined
with HZ=1000 looks a bit weird ;)

Best regards
-- 
                                      Stano