Re: [PATCH V2 0/6][RFC] futex: FUTEX_LOCK with optional adaptivespinning

[Peter Zijlstra]

On Tue, 2010-04-06 at 00:15 +0300, Avi Kivity wrote:
> 
> An interesting (but perhaps difficult to achieve) optimization would be 
> to spin in userspace. 

System call overhead isn't that large, but if you want to amortize that
you can do a very small spin in userspace and then take the syscall:

  try
  spin
  try
  syscall

like.

Complicating anything beyond that is just not worth it.

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