Interrupt latency problems

[Bruce Evans]

On Sun, 11 May 2003, Bakul Shah wrote:

> Is it possible to cheaply check how long a mutex was held?

No, since reading the time can't be done cheaply.

> If it crosses some sysctl var set threshold you can increment
> some count and/or drop into the debugger.  That is one way to
> find all mutex slowpokes.  You can even find a distribution
> by incrementing an array element.  Array indexed by heldtime
> rounded down to multiples of 10ms or so.  Just an idea --
> ignore it if it doesn't make sense!

The MUTEX_PROFILING option implements most of this.

Bruce