linux-kernel - Re: [PATCH 00/14] perf clang: Support compiling BPF script use builtin clang

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Message-ID: <57E87EAA.2090308@huawei.com>
Date:   Mon, 26 Sep 2016 09:49:30 +0800
From:   "Wangnan (F)" <wangnan0@...wei.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     <acme@...nel.org>, <ast@...com>, <pi3orama@....com>,
        <linux-kernel@...r.kernel.org>, <lizefan@...wei.com>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>,
        He Kuang <hekuang@...wei.com>, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH 00/14] perf clang: Support compiling BPF script use
 builtin clang



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.

  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.

  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.

Thank you.