From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933835AbcI0Bu6 (ORCPT ); Mon, 26 Sep 2016 21:50:58 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:59024 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933035AbcI0Buv (ORCPT ); Mon, 26 Sep 2016 21:50:51 -0400 Subject: Re: [PATCH 00/14] perf clang: Support compiling BPF script use builtin clang To: Arnaldo Carvalho de Melo , Alexei Starovoitov References: <1474635001-153850-1-git-send-email-wangnan0@huawei.com> <20160924151559.GA49831@ast-mbp.thefacebook.com> <57E87EAA.2090308@huawei.com> <20160926234701.GA58431@ast-mbp.thefacebook.com> CC: Li Zefan , He Kuang , , , Jiri Olsa , Arnaldo Carvalho de Melo , , From: "Wangnan (F)" Message-ID: <57E9D02A.8060303@huawei.com> Date: Tue, 27 Sep 2016 09:49:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.111.66.109] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.57E9D03A.00E1,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 4696137683ee16eebc4e165d099c361f Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/9/27 7:58, Arnaldo Carvalho de Melo wrote: > > Le 26 sept. 2016 8:47 PM, "Alexei Starovoitov" > > 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.