On Tue, 7 Dec 2021 12:54:04 +0100 (CET) Justin Iurman wrote: > >> The function kmem_cache_size is used to retrieve the size of a slab > >> object. Note that it returns the "object_size" field, not the "size" > >> field. If needed, a new function (e.g., kmem_cache_full_size) could be > >> added to return the "size" field. To match the definition from the > >> draft, the number of bytes is computed as follows: > >> > >> slabinfo.active_objs * size > > > > Implementing the standard is one thing but how useful is this > > in practice? > > IMHO, very useful. To be honest, if I were to implement only a few data > fields, these two would be both included. Take the example of CLT [1] > where the queue length data field is used to detect low-level issues > from inside a L5-7 distributed tracing tool. And this is just one > example among many others. The queue length data field is very specific > to TX queues, but we could also use the buffer occupancy data field to > detect more global loads on a node. Actually, the goal for operators > running their IOAM domain is to quickly detect a problem along a path > and react accordingly (human or automatic action). For example, if you > monitor TX queues along a path and detect an increasing queue on a > router, you could choose to, e.g., rebalance its queues. With the > buffer occupancy, you could detect high-loaded nodes in general and, > e.g., rebalance traffic to another branch. Again, this is just one > example among others. Apart from more accurate ECMPs, you could for > instance deploy a smart (micro)service selection based on different > metrics, etc. > > [1] https://github.com/Advanced-Observability/cross-layer-telemetry Ack, my question was more about whether the metric as implemented provides the best signal. Since the slab cache scales dynamically (AFAIU) it's not really a big deal if it's full as long as there's memory available on the system.
