Re: [MM] Make mm counters per cpu instead of atomic

[Christoph Lameter]

On Mon, 23 Nov 2009, Zhang, Yanmin wrote:

> Another theoretic issue is below scenario:
> Process A get the read lock on cpu 0 and is scheduled to cpu 2 to unlock. Then
> it's scheduled back to cpu 0 to repeat the step. eventually, the reader counter
> will overflow. Considering multiple thread cases, it might be faster to
> overflow than what we imagine. When it overflows, processes will hang there.

True.... We need to find some alternative to per cpu data to scale mmap
sem then.
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