Re: [PATCH 0/4] mm: zone lock tracepoint instrumentation

["Cheatham, Benjamin" <benjamin.cheatham@amd.com>]

On 2/11/2026 9:22 AM, Dmitry Ilvokhin wrote:
> Zone lock contention can significantly impact allocation and
> reclaim latency, as it is a central synchronization point in
> the page allocator and reclaim paths. Improved visibility into
> its behavior is therefore important for diagnosing performance
> issues in memory-intensive workloads.
> 
> On some production workloads at Meta, we have observed noticeable
> zone lock contention. Deeper analysis of lock holders and waiters
> is currently difficult with existing instrumentation.
> 
> While generic lock contention_begin/contention_end tracepoints
> cover the slow path, they do not provide sufficient visibility
> into lock hold times. In particular, the lack of a release-side
> event makes it difficult to identify long lock holders and
> correlate them with waiters. As a result, distinguishing between
> short bursts of contention and pathological long hold times
> requires additional instrumentation.
> 
> This patch series adds dedicated tracepoint instrumentation to
> zone lock, following the existing mmap_lock tracing model.
> 
> The goal is to enable detailed holder/waiter analysis and lock
> hold time measurements without affecting the fast path when
> tracing is disabled.
> 
> The series is structured as follows:
> 
>   1. Introduce zone lock wrappers.
>   2. Mechanically convert zone lock users to the wrappers.
>   3. Convert compaction to use the wrappers (requires minor
>      restructuring of compact_lock_irqsave()).
>   4. Add zone lock tracepoints.

I think you can improve the flow of this series if reorder as follows:
	1. Introduce zone lock wrappers
	4. Add zone lock tracepoints
	2. Mechanically convert zone lock users to the wrappers
	3. Convert compaction to use the wrappers...

and possibly squash 1 & 4 (though that might be too big of a patch). It's better to introduce the
wrappers and their tracepoints together before the reviewer (i.e. me) forgets what was added in
patch 1 by the time they get to patch 4.

Thanks,
Ben