On Mon, 2007-01-29 at 10:15 -0800, Christoph Lameter wrote:
quoted text
> On Mon, 29 Jan 2007, Peter Zijlstra wrote:
> 
> > Ladder locking would end up:
> > 
> > lock A0
> > lock B1
> > unlock A0 -> a new operation can start
> > lock C2
> > unlock B1
> > lock D5
> > unlock C2
> > ** we do stuff to D5
> > unlock D5
> > 
> 
> Instead of taking one lock we would need to take 4?

Yep.

quoted text
> Wont doing so cause significant locking overhead?
> We probably would want to run some benchmarks. 

Right, I was hoping the extra locking overhead would be more than
compensated by the reduction in lock contention time. But testing is
indeed in order.

quoted text
> Maybe disable the scheme for systems with a small number of 
> processors?

CONFIG_RADIX_TREE_CONCURRENT does exactly this.

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