On 10/06/2010 05:16 쾀弮, Matthew Dillon wrote:
[...]
> For the most part these tokens are not going to be held for more than
> 1uS or so, and often quite a bit less then that. This is because
> most kernel operations only take long periods of time because they
> actually block, and of course the token will be released if the thread
> blocks.
>
> Take a vm_fault for example. The fault occurs and then blocks on I/O.
> That might be 200ns. Then later on the I/O completes and the thread
> wakes up and reacquires the token, then spends another 200ns with the
> token held before returning from the fault.
I was thinking more about a soft pagefault, where you might need to
search the VM data structures, do a few allocations and wait for an IPI
roundtrip (for the pagetable invalidation).
Aggelos