> -----Original Message----- > From: dev <dev-boun...@dpdk.org> On Behalf Of Van Haaren, Harry > Sent: Wednesday, September 23, 2020 3:17 PM > To: Mattias Rönnblom <mattias.ronnb...@ericsson.com>; dev@dpdk.org > Cc: david.march...@dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2 1/2] service: add component useful work > attribute > > > -----Original Message----- > > From: Mattias Rönnblom <mattias.ronnb...@ericsson.com> > > Sent: Wednesday, September 23, 2020 12:40 PM > > To: Van Haaren, Harry <harry.van.haa...@intel.com>; dev@dpdk.org > > Cc: david.march...@dpdk.org > > Subject: Re: [dpdk-dev] [PATCH v2 1/2] service: add component useful work > > attribute > > Hi Mattias, > > Thanks for taking time to review & prompt reply!
Ping Mattias - any input based on follow up discussion below? > > On 2020-09-14 16:37, Harry van Haaren wrote: > > > This commit adds a new attribute which allows the service to indicate > > > if the previous iteration of work was "useful". Useful work here implies > > > forward progress was made. > > > > > Exposing this information via an attribute to the application allows > > > tracking of CPU cycles as being useful or not-useful, and a CPU load > > > estimate can be deduced from that information. > > > > > > How would that tracking be implemented? rte_service.c already keeps > > track of the amount of busy cycles per service. Would it be possible to > > reuse that mechanism to achieve the same goal? > > Tracking "busy cycles" is not exactly the same - Eventdev SW PMD can spend > cycles polling, and trying to move packets around its internal queues, but > make > no forward progress. Measuring cycles spent in the service would not indicate > the correct "busyness" in that case. > > In the suggested patchset, each service (e.g Eventdev SW PMD) can update > a statistic itself, pushing an attribute value into the service-cores layer. > This method allows each PMD to define "useful work" in its own way. > > > We did some prototyping on dynamic load balancing for the service core > > framework, and then we extended the API is such a way that the service > > callback would return a bool indicating if forward progress was made, if > > I recall correctly. Sampling these counters allowed for tracking load on > > both a per-lcore and per-service basis. > > The service callback return value can be stored/inspected on the service-core > itself, but how to show that to the application? It still requires an > attribute API > like proposed below re-using "attr_get" API I think. > > So really the only difference in the prototype you mention is how the > service itself communicates business to the service-cores infrastructure in > EAL. > > Perhaps re-purposing return-value is simpler, but it limits statistics from > the > service to just business, and the API change requires all services to change. > > Pros of adding an API as this patchset proposes is to push attribute values to > service-core in EAL is extensibility, and no API breakage. > > Given that context, Ack / push-back to this suggested approach? <snip patch contents>
