Re: [PATCH] Staircase scheduler v7.4

[Nick Piggin <nickpiggin@yahoo.com.au>]

Peter Williams wrote:
> 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.
> 

Well exactly. This is what the standard scheduler tries to do, and
it does have weird starvation and priority problems that pop up.

> 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.

I agree renicing X is helpful.