Re: page table lock patch V15 [0/7]: overview

[Roman Zippel <zippel@xxxxxxxxxxxxxx>]

Hi,

Christoph Lameter wrote:

> Introduction of the cmpxchg is one atomic operations that replaces the two
> spinlock ops typically necessary in an unpatched kernel. Obtaining the
> spinlock requires an spinlock (which is an atomic operation) and then the
> release involves a barrier. So there is a net win for all SMP cases as far
> as I can see.

But there might be a loss in the UP case. Spinlocks are optimized away, 
but your cmpxchg emulation enables/disables interrupts with every access.

bye, Roman
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