Re: -mm seems significanty slower than mainline on kernbench

[Martin Bligh <mbligh@google.com>]

Con Kolivas wrote:
> On Wed, 11 Jan 2006 01:38 pm, Peter Williams wrote:
> 
>>Con Kolivas wrote:
>> > I guess we need to check whether reversing this patch helps.
>>
>>It would be interesting to see if it does.
>>
>>If it does we probably have to wear the cost (and try to reduce it) as
>>without this change smp nice support is fairly ineffective due to the
>>fact that it moves exactly the same tasks as would be moved without it.
>>  At the most it changes the frequency at which load balancing occurs.
> 
> 
> I disagree. I think the current implementation changes the balancing according 
> to nice much more effectively than previously where by their very nature, low 
> priority tasks were balanced more frequently and ended up getting their own 
> cpu. No it does not provide firm 'nice' handling that we can achieve on UP 
> configurations but it is also free in throughput terms and miles better than 
> without it. I would like to see your more robust (and nicer code) solution 
> incorporated but I also want to see it cost us as little as possible. We 
> haven't confirmed anything just yet...

Whether it turns out to be that or not ... 10% is a BIG frigging hit to 
take doing something basic like kernel compilation. Hell, 1% is a big 
hit to take, given the lengths we go to to buy that sort of benefit.

M.