Re: [PATCH] Staircase scheduler v7.4

[Peter Williams <pwil3058@bigpond.net.au>]

Nick Piggin wrote:
> Felipe Alfaro Solana wrote:
> 
>> I have tested 2.6.7-bk10 plus from_2.6.7_to_staircase_7.7 patch and,
>> while it's definitively better than previous versions, it still feels a
>> little jerky when moving windows in X11 wrt to -mm3. Renicing makes it a
>> little bit smoother, but not as much as -mm3 without renicing.
>>
> 
> You know, if renicing X makes it smoother, then that is a good thing
> IMO. X needs large amounts of CPU and low latency in order to get
> good interactivity, which is something the scheduler shouldn't give
> to a process unless it is told to.

I agree.  Although the X servers CPU usage is usually relatively low 
(less than 5%) it does have periods when it can get quite high (greater 
than 80%) for reasonably long periods.  This makes it difficult to come 
up with a set of rules for CPU allocation that makes sure the X server 
gets what it needs (when it needs it) without running the risk of giving 
other tasks with similar load patterns unnecessary and unintentional 
preferential treatment.

However, I think that there is still a need for automatic boosts for 
some tasks.  For instance, programs such as xmms and other media 
streamers are ones whose performance could worsen as a result of the X 
server being reniced unless it is treated specially and the boost they 
are given needs to be enough to put them before the X server in priority 
order.  But renicing X would enable a tightening of the rules that 
govern the automatic dispensing of preferential treatment to tasks that 
are perceived to be interactive which should be good for overall system 
performance.

Peter
-- 
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce