Re: [PATCH 0/2] Add percpu smp cacheline align section

[Christoph Lameter]

On Fri, 4 May 2007, Fenghua Yu wrote:

> This is follow-up for Suresh's runqueue align in smp patch at:
> http://www.uwsg.iu.edu/hypermail/linux/kernel/0704.1/0340.html
> 
> The patches place all of smp cacheline aligned percpu data into 
> .data.percpu.cacheline_aligned_in_smp. Other percpu data is still in 
> data.percpu section. The patches can reduce cache line access in SMP and 
> reduce alignment gap waste. The patches also define PERCPU macro for 
> vmlinux.lds.S for code clean up.

Ummm... The per cpu area is for exclusive use of a particular processor. 
If there is contention in the per cpu area then a data object needs to be 
removed from the per cpu area because the object is *not* accessed only 
from a certain cpu.

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