On Thu, 6 Jan 2022 16:20:05 -0800 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > On Thu, Jan 6, 2022 at 3:52 PM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > On Thu, 6 Jan 2022 09:40:17 -0800 > > Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > > > > On Thu, Jan 6, 2022 at 5:59 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > > > > > That seems to bind your mind. The program type is just a programing > > > > 'model' of the bpf. You can choose the best implementation to provide > > > > equal functionality. 'kprobe' in bpf is just a name that you call some > > > > instrumentations which can probe kernel code. > > > > > > No. We're not going to call it "fprobe" or any other name. > > > From bpf user's pov it's going to be "multi attach kprobe", > > > because this is how everyone got to know kprobes. > > > The 99% usage is at the beginning of the funcs. > > > When users say "kprobe" they don't care how kernel attaches it. > > > The func entry limitation for "multi attach kprobe" is a no-brainer. > > > > Agreed. I think I might mislead you. From the bpf user pov, it always be > > shown as 'multi attached kprobes (but only for the function entry)' > > the 'fprobe' is kernel internal API name. > > > > > And we need both "multi attach kprobe" and "multi attach kretprobe" > > > at the same time. It's no go to implement one first and the other > > > some time later. > > > > You can provide the interface to user space, but the kernel implementation > > is optimized step by step. We can start it with using real multiple > > kretprobes, and then, switch to 'fprobe' after integrating fgraph > > callback. :) > > Sounds good to me. > My point was that users often want to say: > "profile speed of all foo* functions". > To perform such a command a tracer would need to > attach kprobes and kretprobes to all such functions. Yeah, I know. That is more than 10 years issue since systemtap. :) > The speed of attach/detach has to be fast. Yes, that's why I provided register/unregister_kprobes() but it sounds not enough (and maybe not optimized enough because all handlers are same) > Currently tracers artificially limit the regex just because > attach/detach is so slow that the user will likely Ctrl-C > instead of waiting for many seconds. Ah, OK. Anyway I also would like to fix that issue. If user wants only function entry/exit, it should be done by ftrace. But since the syntax (and user's mind model) it should be done via 'kprobe', so transparently converting such request to ftrace is needed. Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
