Messages in this thread | | | Subject | Re: [PATCH 00/14] perf clang: Support compiling BPF script use builtin clang | From | "Wangnan (F)" <> | Date | Tue, 27 Sep 2016 09:49:30 +0800 |
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On 2016/9/27 7:58, Arnaldo Carvalho de Melo wrote: > > Le 26 sept. 2016 8:47 PM, "Alexei Starovoitov" > <alexei.starovoitov@gmail.com <mailto:alexei.starovoitov@gmail.com>> a > écrit : > > > > On Mon, Sep 26, 2016 at 09:49:30AM +0800, Wangnan (F) wrote: > > > > > > > > > On 2016/9/24 23:16, Alexei Starovoitov wrote: > > > >On Fri, Sep 23, 2016 at 12:49:47PM +0000, Wang Nan wrote: > > > >>This patch set is the first step to implement features I announced > > > >>in LinuxCon NA 2016. See page 31 of: > > > >> > > > >> > http://events.linuxfoundation.org/sites/events/files/slides/Performance%20Monitoring%20and%20Analysis%20Using%20perf%20and%20BPF_1.pdf > > > >> > > > >>This patch set links LLVM and Clang libraries to perf, so perf > > > >>is able to compile BPF script to BPF object on the fly. > > > >Nice! > > > >So single perf binary won't have llvm external dependency anymore > > > >or both ways will be maintained? > > > >The command line stays the same? > > > > > > Yes. This patch set doesn't change interface. It compiles BPF script > > > with builtin clang, and if it fail, fall back to external clang. > > > > > > >If I understand the patches correctly, this set is establishing > > > >the basic functionality and more complex features coming? > > > > > > > > > > Yes. Following steps are: > > > > > > 1. Ease of use improvement: automatically include BPF functions > > > declaration and macros. > > > > +1 > > > > > 2. Perf's hook: compile part of BPF script into native code, run > > > them in perf when something happen. Create a channel, coordinate > > > BPF and native code use bpf-output event. > > > > +1 > > > > > 3. Define a new language to support common profiling task. I'm not > > > very clear what the new language should be. It may looks like lua, > > > perf converts it to C then to LLVM IR with builtin clang. > > > > Many tracing languages were invented in the past. > > At this point I'm not sure what exactly new language will solve. > > To make it easier to write bpf programs? > > I think it will be more fruitful to tweak clang/llvm to add > > good warnings/errors for cases where we know that C is not going > > be compiled into the code that the kernel verifier will accept. > > Like we can complain about loops, unitialized variables, > > non-inlined and unkown helper functions... all from clang/llvm. > > imo that would be the better path forward and will help > > both tracing and networking users that write in this restricted C. > > ++1 > > >
OK. Now let's focus on the first two goals. After that let's consider how to help writing BPF program.
Thank you.
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