On Mon, Mar 09, 2026 at 02:21:42PM +0000, Dmitry Ilvokhin wrote: > On Mon, Mar 09, 2026 at 01:10:46PM +0000, Matthew Wilcox wrote: > > On Fri, Feb 27, 2026 at 04:00:22PM +0000, Dmitry Ilvokhin wrote: > > > This patch series adds dedicated tracepoint instrumentation to > > > zone lock, following the existing mmap_lock tracing model. > > > > I don't like this at all. We have CONFIG_LOCK_STAT. That should be > > improved insted of coming up with one-offs for every single lock > > that someone deems "special". > > Thanks for the feedback, Matthew. > > CONFIG_LOCK_STAT provides useful statistics, but it is primarily a > debug facility and is generally too heavyweight for the production > environments.
Yes, agreed. I think that is what needs to change. > The motivation for this series was to provide lightweight observability > for the zone lock in production workloads. I read that. But first it was the mmap lock. Now it's the zone lock. Which lock will be next? This is too heavyweight a procedure to follow for each lock of interest. > I agree that improving generic lock instrumentation would be preferable. > I did consider whether something similar could be done generically for > spinlocks, but the unlock path there is typically just a single atomic > store, so adding generic lightweight instrumentation without affecting > the fast path is difficult. This is why we have tracepoint_enabled() and friends. But ... LOCK_STAT doesn't affect the unlock path at all. It only changes the acquire side to call lock_acquired() (and lock_contended() if the trylock failed). > In parallel, I've been experimenting with improving observability for > sleepable locks by adding a contended_release tracepoint, which would > allow correlating lock holders and waiters in a more generic way. I've > posted an RFC here: > > https://lore.kernel.org/all/[email protected]/ > > I'd appreciate feedback on whether that direction makes sense for > improving the generic lock tracing infrastructure. It seems fine to me, but I don't have the depth in the locking code to give it the thorough review it deserves.
