----- On Feb 5, 2021, at 10:40 AM, Peter Zijlstra peterz@xxxxxxxxxxxxx wrote: > On Fri, Feb 05, 2021 at 10:09:26AM -0500, Mathieu Desnoyers wrote: >> Then we should be able to generate the following using static keys as a >> jump table and N static calls: >> >> jump <static key label target> >> label_N: >> stack setup >> call >> label_N-1: >> stack setup >> call >> label_N-2: >> stack setup >> call >> ... >> label_0: >> jump end >> label_fallback: >> <iteration and indirect calls> >> end: >> >> So the static keys would be used to jump to the appropriate label (using >> a static branch, which has pretty much 0 overhead). Static calls would >> be used to implement each of the calls. >> >> Thoughts ? > > At some point I tried to extend the static_branch infra to do multiple > targets and while the low level plumbing is trivial, I ran into trouble > trying to get a sane C level API for it. Did you try doing an API for a variable number of targets, or was it for a specific number of targets ? It might be easier to just duplicate some of the API code for number of targets between 2 and 12, and let the users code choose the maximum number of targets they want to accelerate. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
