Message-ID: <555A3FC2.8060805@plumgrid.com>
Date: Mon, 18 May 2015 12:38:42 -0700
From: Alexei Starovoitov <ast@plumgrid.com>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.6.0
MIME-Version: 1.0
To: Wang Nan <wangnan0@huawei.com>, paulus@samba.org, a.p.zijlstra@chello.nl,
        mingo@redhat.com, acme@kernel.org, namhyung@kernel.org,
        jolsa@kernel.org, dsahern@gmail.com, daniel@iogearbox.net,
        brendan.d.gregg@gmail.com, masami.hiramatsu.pt@hitachi.com
CC: lizefan@huawei.com, linux-kernel@vger.kernel.org, pi3orama@163.com
Subject: Re: [RFC PATCH v3 00/37] perf tools: introduce 'perf bpf' command
 to load eBPF programs.
References: <1431860222-61636-1-git-send-email-wangnan0@huawei.com>
In-Reply-To: <1431860222-61636-1-git-send-email-wangnan0@huawei.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2027
Lines: 50

On 5/17/15 3:56 AM, Wang Nan wrote:
> This is the 3rd version of 'perf bpf' patch series, based on
> v4.1-rc3.
>
> The goal of this series of patches is to integrate eBPF with perf.
> After applying these patches, users are allowed to use following
> command to load eBPF program compiled by LLVM into kernel then start
> recording with filters on:
>
>   # perf bpf record --object sample_bpf.o -- -a sleep 4

I think using programs are sophisticated filters is a good start
and are useful already. Let's focus on that at the moment.
I wouldn't grow the patchset any bigger.

> Other than the previous change, v3 patch series drops the '|' event
> syntax introduced in v2, because I realized that in v2 users are
> allowed to pass any bpf fd by using it, like:
>
>   # perf bpf record -- -e sched:sched_switch|100| sleep 1
>
> which may become trouble maker.

passing fd number as a string is an odd interface anyway.
So I think that was the right call. We can improve it later.

>   Are we actually need a 'perf bpf' command? We can get similar result by
>   modifying 'perf record' to make it load eBPF program before recording.
>
>   I suggest to keep 'perf bpf', group all eBPF stuffs together using a
>   uniform entry. Also, eBPF programs can act not only as filters but also
>   data aggregator. It is possible to make something link 'perf bpf run'
>   to simply make it run, and dump result after user hit 'C-c' or timeout.

Though it's tempting to group under 'perf bpf'. I think it's cleaner to
add --object flag to 'perf record'
Since it will avoid unnecessary '--'.
Unless we can drop it? Like
perf bpf record --object sample_bpf.o -a sleep 4
should work?
If not, then the following is better:
perf record --object sample_bpf.o -a sleep 4

Thank you for the hard work!

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/