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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Kris Van Hees <kris.van.hees@oracle.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	dtrace-devel@oss.oracle.com, linux-kernel@vger.kernel.org,
	rostedt@goodmis.org, mhiramat@kernel.org, acme@kernel.org,
	ast@kernel.org, daniel@iogearbox.net, peterz@infradead.org
Subject: Re: [RFC PATCH 00/11] bpf, trace, dtrace: DTrace BPF program type implementation and sample use
Date: Wed, 22 May 2019 13:16:25 -0700
Message-ID: <20190522201624.eza3pe2v55sn2t2w@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20190522041253.GM2422@oracle.com>

On Wed, May 22, 2019 at 12:12:53AM -0400, Kris Van Hees wrote:
> 
> Could you elaborate on why you believe my patches are not adding generic
> features?  I can certainly agree that the DTrace-specific portions are less
> generic (although they are certainly available for anyone to use), but I
> don't quite understand why the new features are deemed non-generic and why
> you believe no one else can use this?

And once again your statement above contradicts your own patches.
The patch 2 adds new prog type BPF_PROG_TYPE_DTRACE and the rest of the patches
are tying everything to it.
This approach contradicts bpf philosophy of being generic execution engine
and not favoriting one program type vs another.

I have nothing against dtrace language and dtrace scripts.
Go ahead and compile them into bpf.
All patches to improve bpf infrastructure are very welcomed.

In particular you brought up a good point that there is a use case
for sharing a piece of bpf program between kprobe and tracepoint events.
The better way to do that is via bpf2bpf call.
Example:
void bpf_subprog(arbitrary args)
{
}

SEC("kprobe/__set_task_comm")
int bpf_prog_kprobe(struct pt_regs *ctx)
{
  bpf_subprog(...);
}

SEC("tracepoint/sched/sched_switch")
int bpf_prog_tracepoint(struct sched_switch_args *ctx)
{
  bpf_subprog(...);
}

Such configuration is not supported by the verifier yet.
We've been discussing it for some time, but no work has started,
since there was no concrete use case.
If you can work on adding support for it everyone will benefit.

Could you please consider doing that as a step forward?


  reply index

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20 23:47 Kris Van Hees
2019-05-21 17:56 ` Alexei Starovoitov
2019-05-21 18:41   ` Kris Van Hees
2019-05-21 20:55     ` Alexei Starovoitov
2019-05-21 21:36       ` Steven Rostedt
2019-05-21 21:43         ` Alexei Starovoitov
2019-05-21 21:48           ` Steven Rostedt
2019-05-22  5:23             ` Kris Van Hees
2019-05-22 20:53               ` Alexei Starovoitov
2019-05-23  5:46                 ` Kris Van Hees
2019-05-23 21:13                   ` Alexei Starovoitov
2019-05-23 23:02                     ` Steven Rostedt
2019-05-24  0:31                       ` Alexei Starovoitov
2019-05-24  1:57                         ` Steven Rostedt
2019-05-24  2:08                           ` Alexei Starovoitov
2019-05-24  2:40                             ` Steven Rostedt
2019-05-24  5:26                             ` Kris Van Hees
2019-05-24  5:10                       ` Kris Van Hees
2019-05-24  4:05                     ` Kris Van Hees
2019-05-24 13:28                       ` Steven Rostedt
2019-05-21 21:36       ` Kris Van Hees
2019-05-21 23:26         ` Alexei Starovoitov
2019-05-22  4:12           ` Kris Van Hees
2019-05-22 20:16             ` Alexei Starovoitov [this message]
2019-05-23  5:16               ` Kris Van Hees
2019-05-23 20:28                 ` Alexei Starovoitov
2019-05-30 16:15                   ` Kris Van Hees
2019-05-31 15:25                     ` Chris Mason
2019-06-06 20:58                       ` Kris Van Hees
2019-06-18  1:25                   ` Kris Van Hees
2019-06-18  1:32                     ` Alexei Starovoitov
2019-06-18  1:54                       ` Kris Van Hees
2019-06-18  3:01                         ` Alexei Starovoitov
2019-06-18  3:19                           ` Kris Van Hees
2019-05-22 14:25   ` Peter Zijlstra
2019-05-22 18:22     ` Kris Van Hees
2019-05-22 19:55       ` Alexei Starovoitov
2019-05-22 20:20         ` David Miller
2019-05-23  5:19         ` Kris Van Hees
2019-05-24  7:27       ` Peter Zijlstra
2019-05-21 20:39 ` [RFC PATCH 01/11] bpf: context casting for tail call Kris Van Hees
2019-05-21 20:39 ` [RFC PATCH 02/11] bpf: add BPF_PROG_TYPE_DTRACE Kris Van Hees
2019-05-21 20:39 ` [RFC PATCH 03/11] bpf: export proto for bpf_perf_event_output helper Kris Van Hees
     [not found] ` <facilities>
2019-05-21 20:39   ` [RFC PATCH 04/11] trace: initial implementation of DTrace based on kernel Kris Van Hees
2019-05-21 20:39 ` [RFC PATCH 05/11] trace: update Kconfig and Makefile to include DTrace Kris Van Hees
     [not found] ` <features>
2019-05-21 20:39   ` [RFC PATCH 06/11] dtrace: tiny userspace tool to exercise DTrace support Kris Van Hees
2019-05-21 20:39 ` [RFC PATCH 07/11] bpf: implement writable buffers in contexts Kris Van Hees
2019-05-21 20:39 ` [RFC PATCH 08/11] perf: add perf_output_begin_forward_in_page Kris Van Hees
     [not found] ` <the>
     [not found]   ` <context>
2019-05-21 20:39     ` [RFC PATCH 09/11] bpf: mark helpers explicitly whether they may change Kris Van Hees
     [not found] ` <helpers>
2019-05-21 20:39   ` [RFC PATCH 10/11] bpf: add bpf_buffer_reserve and bpf_buffer_commit Kris Van Hees
2019-05-21 20:40 ` [RFC PATCH 11/11] dtrace: make use of writable buffers in BPF Kris Van Hees
2019-05-21 20:48 ` [RFC PATCH 00/11] bpf, trace, dtrace: DTrace BPF program type implementation and sample use Kris Van Hees
2019-05-21 20:54   ` Steven Rostedt
2019-05-21 20:56   ` Alexei Starovoitov

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