[PATCH] os: Turn off the scheduler alarm after an arbitrary length of time

[Vignatti Tiago (Nokia-MS/Helsinki)]

On Mon, Aug 02, 2010 at 07:34:57PM +0200, ext Adam Jackson wrote:
> On Mon, 2010-08-02 at 17:40 +0300, Tiago Vignatti wrote:
> > just wondering what made you think 10 is a good number?
> 
> I'd be lying if I said I thought very hard about it.  The way the
> defaults work out, the maximum timeslice is 200ms, which is 10 times as
> long as the scheduler tick.  Another 10x is 2 seconds, which is:
> 
> - well into "wtf why is it stuck" territory
> - a bit before anyone would have thought to attach strace
> - long enough that no amount of scheduler punishment will improve the
>   user experience
> 
> But it's not something that's interesting to be precise about.

I understand your intention to shut up SIGALRM in strace when a client is
doing a busy rendering. But I'm afraid adding this feature will impact in the
overall scheduling - not that we're doing great on this area, but would
require more study to see if this prioritization of a busy client doesn't
negatively affects other clients... it's just hard to validate your changes.

BTW, I didn't tried your patch, but are you sure this works as expected? If I
understood correctly, this only works for single large requests and for other
cases SmartScheduleStartTimer is going to be called always after another
request wakes the server, re-starting the SIGALRM madness. So if there's
always chunks of large requests you're going to see SIGALRM handler anyway.


Cheers,
             Tiago