Hi Paul, On Thu, Feb 10, 2022 at 12:10 PM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > On Thu, Feb 10, 2022 at 02:27:11PM -0500, Waiman Long wrote: > > On 2/10/22 14:14, Paul E. McKenney wrote: > > > On Thu, Feb 10, 2022 at 10:13:53AM +0100, Peter Zijlstra wrote: > > > > On Wed, Feb 09, 2022 at 04:32:58PM -0800, Namhyung Kim wrote: > > > > > On Wed, Feb 9, 2022 at 1:09 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > > > 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. > > > > > If it's only lockref, is it possible to change it to use arch_spinlock_t > > > > > so that it can remain in 4 bytes? It'd be really nice if we can keep > > > > > spin lock size, but it'd be easier to carry the name with it for > > > > > analysis IMHO. > > > > It's just vile and disgusting to blow up the lock size for convenience > > > > like this. > > > > > > > > And no, there's more of that around. A lot of effort has been spend to > > > > make sure spinlocks are 32bit and we're not going to give that up for > > > > something as daft as this. > > > > > > > > Just think harder on the analysis side. Like said; I'm thinking the > > > > caller IP should be good enough most of the time. > > > > > > Another option is to keep any additional storage in a separate data > > > structure keyed off of lock address, lockdep class, or whatever. > > > > > > Whether or not this is a -good- option, well, who knows? ;-) > > > > I have suggested that too. Unfortunately, I was replying to an email with > > your wrong email address. So you might not have received it. > > Plus I was too lazy to go look at lore. ;-) Sorry for the noise about the email address in the first place. It has been so long since the last time I sent you a patch.. Thanks, Namhyung
