Re: [RFC 00/12] locking: Separate lock tracepoints from lockdep/lock_stat (v1)

Peter Zijlstra
2022-02-09T09:10:23Z

On Tue, Feb 08, 2022 at 10:41:56AM -0800, Namhyung Kim wrote:

> Eventually I'm mostly interested in the contended locks only and I
> want to reduce the overhead in the fast path. By moving that, it'd be
> easy to track contended locks with timing by using two tracepoints.

So why not put in two new tracepoints and call it a day?

Why muck about with all that lockdep stuff just to preserve the name
(and in the process continue to blow up data structures etc..). This
leaves distros in a bind, will they enable this config and provide
tracepoints while bloating the data structures and destroying things
like lockref (which relies on sizeof(spinlock_t)), or not provide this
at all.

Yes, the name is convenient, but it's just not worth it IMO. It makes
the whole proposition too much of a trade-off.

Would it not be possible to reconstruct enough useful information from
the lock callsite?