Hi Dietmar On 09/02/20 12:44, Dietmar Eggemann wrote: > + Phil Auld <pa...@redhat.com> > > On 28/08/2020 19:26, Qais Yousef wrote: > > On 08/28/20 19:10, Dietmar Eggemann wrote: > >> On 28/08/2020 12:27, Qais Yousef wrote: > >>> On 08/28/20 10:00, vincent.donnef...@arm.com wrote: > >>>> From: Vincent Donnefort <vincent.donnef...@arm.com> > > [...] > > >> Can you remind me why we have all these helper functions like > >> sched_trace_rq_cpu_capacity? > > > > struct rq is defined in kernel/sched/sched.h. It's not exported. Exporting > > these helper functions was the agreement to help modules trace internal > > info. > > By passing generic info you decouple the tracepoint from giving specific > > info > > and allow the modules to extract all the info they need from the same > > tracepoint. IE: if you need more than just cpu_capacity from this > > tracepoint, > > you can get that without having to continuously add extra arguments > > everytime > > you need an extra piece of info. Unless this info is not in the rq of > > course. > > I think this decoupling is not necessary. The natural place for those > scheduler trace_event based on trace_points extension files is > kernel/sched/ and here the internal sched.h can just be included. > > If someone really wants to build this as an out-of-tree module there is > an easy way to make kernel/sched/sched.h visible. > > CFLAGS_sched_tp.o := -I$KERNEL_SRC/kernel/sched > > all: > make -C $KERNEL_SRC M=$(PWD) modules
Sorry for the late response. Was on holiday. IMHO the above is a hack. Out-of-tree modules should rely on public headers and exported functions only. What you propose means that people who want to use these tracepoints in meaningful way must have a prebuilt kernel handy. Which is maybe true for us who work in the embedded world. But users who run normal distro kernels (desktop/servers) will fail to build against `/lib/modules/$(uname -r)/build` where that internal header file is not exported. IOW, we're putting extra hoops for a large class of users here to be able to access these internal data. They have to maintain their out-of-tree definition of these structures. FWIW, I did raise this concern with Peter in 2019 OSPM and he was okay with the exports as it's still not a contract and they can disappear anytime we want. Migrating to using BTF is the right way forward IMO. I don't think what we have here is out-of-control yet. Though I agree they're annoying. Cheers -- Qais Yousef
