On Tue, 21 Dec 2021 19:23:37 +0200 Vladimir Oltean wrote: > On Tue, Dec 21, 2021 at 06:06:39PM +0100, Justin Iurman wrote: > > On Dec 10, 2021, at 1:38 AM, Jakub Kicinski kuba@xxxxxxxxxx wrote: > > > I think we're on the same page, the main problem is I've not seen > > > anyone use the skbuff_head_cache occupancy as a signal in practice. > > > > > > I'm adding a bunch of people to the CC list, hopefully someone has > > > an opinion one way or the other. > > > > It looks like we won't have more opinions on that, unfortunately. > > > > @Jakub - Should I submit it as a PATCH and see if we receive more > > feedback there? > > I know nothing about OAM and therefore did not want to comment, but I > think the point raised about the metric you propose being irrelevant in > the context of offloaded data paths is quite important. The "devlink-sb" > proposal was dismissed very quickly on grounds of requiring sleepable > context, is that a deal breaker, and if it is, why? Not only offloaded > interfaces like switches/routers can report buffer occupancy. Plain NICs > also have buffer pools, DMA RX/TX rings, MAC FIFOs, etc, that could > indicate congestion or otherwise high load. Maybe slab information could > be relevant, for lack of a better option, on virtual interfaces, but if > they're physical, why limit ourselves on reporting that? The IETF draft > you present says "This field indicates the current status of the > occupancy of the common buffer pool used by a set of queues." It appears > to me that we could try to get a reporting that has better granularity > (per interface, per queue) than just something based on > skbuff_head_cache. What if someone will need that finer granularity in > the future. Indeed. In my experience finding meaningful metrics is heard, the chances that something that seems useful on the surface actually provides meaningful signal in deployments is a lot lower than one may expect. And the commit message reads as if the objective was checking a box in the implemented IOAM metrics, rather exporting relevant information. We can do a roll call on people CCed but I read their silence as nobody thinks this metric is useful. Is there any experimental data you can point to which proves the signal strength?
