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Date: Tue, 7 Jul 2015 17:16:56 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Wang Nan <wangnan0@huawei.com>
Cc: ast@plumgrid.com, brendan.d.gregg@gmail.com, daniel@iogearbox.net,
        Namhyung Kim <namhyung@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>, David Ahern <dsahern@gmail.com>,
        linux-kernel@vger.kernel.org, lizefan@huawei.com, hekuang@huawei.com,
        xiakaixu@huawei.com, pi3orama@163.com
Subject: Re: [RFC PATCH v10 23/50] perf tools: Make perf depend on libbpf
Message-ID: <20150707201656.GE3135@kernel.org>
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Em Tue, Jul 07, 2015 at 04:54:52PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Jul 01, 2015 at 02:14:11AM +0000, Wang Nan escreveu:
> > By adding libbpf into perf's Makefile, this patch enables perf to
> > build libbpf during building if libelf is found and neither NO_LIBELF
> > nor NO_LIBBPF is set. The newly introduced code is similar to libapi
> > and libtraceevent building in Makefile.perf.

> > MANIFEST is also updated for 'make perf-*-src-pkg'.

> > Append make_no_libbpf to tools/perf/tests/make.

> > 'bpf' feature check is appended into default FEATURE_TESTS and
> > FEATURE_DISPLAY, so perf will check API version of bpf in
> > /path/to/kernel/include/uapi/linux/bpf.h. Which should not fail
> > except when we are trying to port this code to an old kernel.
> > 
> > Error messages are also updated to notify users about the disable of
> > BPF support of 'perf record' if libelf is missed or BPF API check
> > failed.
> 
> Much better!

<SNIP>

> Auto-detecting system features:

<SNIP>

> ...                           bpf: [ on  ]

<SNIP>

But... I was all happy about this being linked with perf, went straight
ahead to try to use it! No, its not possible, I have to go thru a series
of other patches first... anticlimactic :-(

So, please move this to just before we can use it, wiring it up should
mean, hey, try this "hello, world" eBPF program right now!

And please consider using the patches in the tmp.perf/ebpf branch in my
tree, the code contents are the same as yours, but I did some changes to
the comment texts, fixing some typos, etc.

Also I fixed up the first two patches, the ones for the kernel, as it
was conflicting with some patches, including one where Steven Rostedt
renamed some trace_events structs and file names, that previously had
"ftrace" in it.

Also next time please leave all this in a git branch I can try, to be
able to try the end result, doing that may help me while doing the next
review.

I'll have to stop for today, will try as soon as you address the
comments to go back working on this.

Thanks!

- Arnaldo
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