From: Steven Rostedt <rostedt@goodmis.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Florent Revest <revest@chromium.org>,
linux-trace-kernel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
bpf <bpf@vger.kernel.org>, Sven Schnelle <svens@linux.ibm.com>,
Alexei Starovoitov <ast@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Alan Maguire <alan.maguire@oracle.com>,
Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>, Guo Ren <guoren@kernel.org>
Subject: Re: [PATCH v9 00/36] tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph
Date: Sun, 28 Apr 2024 19:25:49 -0400 [thread overview]
Message-ID: <20240428192549.7898bf6b@rorschach.local.home> (raw)
In-Reply-To: <CAEf4BzYMToveELxsOJ9dXz3H-9omhxRLKgGK-ppYvmK8pgDsfA@mail.gmail.com>
On Thu, 25 Apr 2024 13:31:53 -0700
Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
I'm just coming back from Japan (work and then a vacation), and
catching up on my email during the 6 hour layover in Detroit.
> Hey Masami,
>
> I can't really review most of that code as I'm completely unfamiliar
> with all those inner workings of fprobe/ftrace/function_graph. I left
> a few comments where there were somewhat more obvious BPF-related
> pieces.
>
> But I also did run our BPF benchmarks on probes/for-next as a baseline
> and then with your series applied on top. Just to see if there are any
> regressions. I think it will be a useful data point for you.
>
> You should be already familiar with the bench tool we have in BPF
> selftests (I used it on some other patches for your tree).
I should get familiar with your tools too.
>
> BASELINE
> ========
> kprobe : 24.634 ± 0.205M/s
> kprobe-multi : 28.898 ± 0.531M/s
> kretprobe : 10.478 ± 0.015M/s
> kretprobe-multi: 11.012 ± 0.063M/s
>
> THIS PATCH SET ON TOP
> =====================
> kprobe : 25.144 ± 0.027M/s (+2%)
> kprobe-multi : 28.909 ± 0.074M/s
> kretprobe : 9.482 ± 0.008M/s (-9.5%)
> kretprobe-multi: 13.688 ± 0.027M/s (+24%)
>
> These numbers are pretty stable and look to be more or less representative.
Thanks for running this.
>
> As you can see, kprobes got a bit faster, kprobe-multi seems to be
> about the same, though.
>
> Then (I suppose they are "legacy") kretprobes got quite noticeably
> slower, almost by 10%. Not sure why, but looks real after re-running
> benchmarks a bunch of times and getting stable results.
>
> On the other hand, multi-kretprobes got significantly faster (+24%!).
> Again, I don't know if it is expected or not, but it's a nice
> improvement.
>
> If you have any idea why kretprobes would get so much slower, it would
> be nice to look into that and see if you can mitigate the regression
> somehow. Thanks!
My guess is that this patch set helps generic use cases for tracing the
return of functions, but will likely add more overhead for single use
cases. That is, kretprobe is made to be specific for a single function,
but kretprobe-multi is more generic. Hence the generic version will
improve at the sacrifice of the specific function. I did expect as much.
That said, I think there's probably a lot of low hanging fruit that can
be done to this series to help improve the kretprobe performance. I'm
not sure we can get back to the baseline, but I'm hoping we can at
least make it much better than that 10% slowdown.
I'll be reviewing this patch set this week as I recover from jetlag.
-- Steve
next prev parent reply other threads:[~2024-04-28 23:25 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-15 12:48 [PATCH v9 00/36] tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph Masami Hiramatsu (Google)
2024-04-15 12:49 ` [PATCH v9 01/36] tracing: Add a comment about ftrace_regs definition Masami Hiramatsu (Google)
2024-04-24 12:23 ` Florent Revest
2024-04-24 13:19 ` Florent Revest
2024-04-24 14:31 ` Masami Hiramatsu
2024-04-15 12:49 ` [PATCH v9 02/36] tracing: Rename ftrace_regs_return_value to ftrace_regs_get_return_value Masami Hiramatsu (Google)
2024-04-15 12:49 ` [PATCH v9 03/36] x86: tracing: Add ftrace_regs definition in the header Masami Hiramatsu (Google)
2024-04-15 12:49 ` [PATCH v9 04/36] function_graph: Convert ret_stack to a series of longs Masami Hiramatsu (Google)
2024-04-15 12:49 ` [PATCH v9 05/36] fgraph: Use BUILD_BUG_ON() to make sure we have structures divisible by long Masami Hiramatsu (Google)
2024-04-15 12:50 ` [PATCH v9 06/36] function_graph: Add an array structure that will allow multiple callbacks Masami Hiramatsu (Google)
2024-04-15 12:50 ` [PATCH v9 07/36] function_graph: Allow multiple users to attach to function graph Masami Hiramatsu (Google)
2024-04-20 3:52 ` Steven Rostedt
2024-04-20 8:56 ` Masami Hiramatsu
2024-04-15 12:50 ` [PATCH v9 08/36] function_graph: Remove logic around ftrace_graph_entry and return Masami Hiramatsu (Google)
2024-04-15 12:50 ` [PATCH v9 09/36] ftrace/function_graph: Pass fgraph_ops to function graph callbacks Masami Hiramatsu (Google)
2024-04-15 12:50 ` [PATCH v9 10/36] ftrace: Allow function_graph tracer to be enabled in instances Masami Hiramatsu (Google)
2024-04-15 12:51 ` [PATCH v9 11/36] ftrace: Allow ftrace startup flags exist without dynamic ftrace Masami Hiramatsu (Google)
2024-04-15 12:51 ` [PATCH v9 12/36] function_graph: Have the instances use their own ftrace_ops for filtering Masami Hiramatsu (Google)
2024-04-15 12:51 ` [PATCH v9 13/36] function_graph: Use a simple LRU for fgraph_array index number Masami Hiramatsu (Google)
2024-04-15 12:51 ` [PATCH v9 14/36] function_graph: Add "task variables" per task for fgraph_ops Masami Hiramatsu (Google)
2024-04-15 12:51 ` [PATCH v9 15/36] function_graph: Move set_graph_function tests to shadow stack global var Masami Hiramatsu (Google)
2024-04-15 12:52 ` [PATCH v9 16/36] function_graph: Move graph depth stored data " Masami Hiramatsu (Google)
2024-04-15 12:52 ` [PATCH v9 17/36] function_graph: Move graph notrace bit " Masami Hiramatsu (Google)
2024-04-15 12:52 ` [PATCH v9 18/36] function_graph: Implement fgraph_reserve_data() and fgraph_retrieve_data() Masami Hiramatsu (Google)
2024-04-15 12:52 ` [PATCH v9 19/36] function_graph: Add selftest for passing local variables Masami Hiramatsu (Google)
2024-04-15 12:52 ` [PATCH v9 20/36] ftrace: Add multiple fgraph storage selftest Masami Hiramatsu (Google)
2024-04-15 12:53 ` [PATCH v9 21/36] function_graph: Pass ftrace_regs to entryfunc Masami Hiramatsu (Google)
2024-04-15 12:53 ` [PATCH v9 22/36] function_graph: Replace fgraph_ret_regs with ftrace_regs Masami Hiramatsu (Google)
2024-04-15 12:53 ` [PATCH v9 23/36] function_graph: Pass ftrace_regs to retfunc Masami Hiramatsu (Google)
2024-04-15 12:53 ` [PATCH v9 24/36] fprobe: Use ftrace_regs in fprobe entry handler Masami Hiramatsu (Google)
2024-04-15 12:53 ` [PATCH v9 25/36] fprobe: Use ftrace_regs in fprobe exit handler Masami Hiramatsu (Google)
2024-04-15 12:54 ` [PATCH v9 26/36] tracing: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs Masami Hiramatsu (Google)
2024-04-15 12:54 ` [PATCH v9 27/36] tracing: Add ftrace_fill_perf_regs() for perf event Masami Hiramatsu (Google)
2024-04-15 12:54 ` [PATCH v9 28/36] tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS Masami Hiramatsu (Google)
2024-04-15 12:54 ` [PATCH v9 29/36] bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled Masami Hiramatsu (Google)
2024-04-25 20:09 ` Andrii Nakryiko
2024-04-29 14:57 ` Masami Hiramatsu
2024-04-15 12:54 ` [PATCH v9 30/36] ftrace: Add CONFIG_HAVE_FTRACE_GRAPH_FUNC Masami Hiramatsu (Google)
2024-04-15 12:55 ` [PATCH v9 31/36] fprobe: Rewrite fprobe on function-graph tracer Masami Hiramatsu (Google)
2024-04-15 12:55 ` [PATCH v9 32/36] tracing/fprobe: Remove nr_maxactive from fprobe Masami Hiramatsu (Google)
2024-04-15 12:55 ` [PATCH v9 33/36] selftests: ftrace: Remove obsolate maxactive syntax check Masami Hiramatsu (Google)
2024-04-15 12:55 ` [PATCH v9 34/36] selftests/ftrace: Add a test case for repeating register/unregister fprobe Masami Hiramatsu (Google)
2024-04-15 12:55 ` [PATCH v9 35/36] Documentation: probes: Update fprobe on function-graph tracer Masami Hiramatsu (Google)
2024-04-15 12:55 ` [PATCH v9 36/36] fgraph: Skip recording calltime/rettime if it is not nneeded Masami Hiramatsu (Google)
2024-04-25 20:15 ` Andrii Nakryiko
2024-04-29 14:56 ` Masami Hiramatsu
2024-04-19 5:36 ` [PATCH v9 00/36] tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph Masami Hiramatsu
2024-04-19 8:01 ` Steven Rostedt
2024-04-24 13:35 ` Florent Revest
2024-04-25 15:10 ` Masami Hiramatsu
2024-04-25 20:31 ` Andrii Nakryiko
2024-04-28 23:25 ` Steven Rostedt [this message]
2024-04-29 20:28 ` Andrii Nakryiko
2024-04-29 13:51 ` Masami Hiramatsu
2024-04-29 20:25 ` Andrii Nakryiko
2024-04-30 13:32 ` Masami Hiramatsu
2024-04-30 16:29 ` Andrii Nakryiko
2024-05-02 2:06 ` Masami Hiramatsu
2024-05-07 21:04 ` Andrii Nakryiko
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