From: Jiri Olsa <jolsa@redhat.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: "Björn Töpel" <bjorn.topel@gmail.com>,
"Jiri Olsa" <jolsa@kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
Netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
"Andrii Nakryiko" <andriin@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Song Liu" <songliubraving@fb.com>,
"Martin KaFai Lau" <kafai@fb.com>,
"Jakub Kicinski" <kuba@kernel.org>,
"David Miller" <davem@redhat.com>,
"Björn Töpel" <bjorn.topel@intel.com>,
"John Fastabend" <john.fastabend@gmail.com>,
"Jesper Dangaard Brouer" <hawk@kernel.org>
Subject: Re: [PATCH 00/14] bpf: Add trampoline and dispatcher to /proc/kallsyms
Date: Wed, 12 Feb 2020 23:40:39 +0100 [thread overview]
Message-ID: <20200212224039.GA233036@krava> (raw)
In-Reply-To: <20200212133125.GA22501@kernel.org>
On Wed, Feb 12, 2020 at 10:31:25AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Wed, Feb 12, 2020 at 12:13:46PM +0100, Jiri Olsa escreveu:
> > On Tue, Feb 11, 2020 at 04:32:23PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Historically vmlinux was preferred because it contains function sizes,
> > > but with all these out of the blue symbols, we need to prefer starting
> > > with /proc/kallsyms and, as we do now, continue getting updates via
> > > PERF_RECORD_KSYMBOL.
>
> > > Humm, but then trampolines don't generate that, right? Or does it? If it
> > > doesn't, then we will know about just the trampolines in place when the
> > > record/top session starts, reparsing /proc/kallsyms periodically seems
> > > excessive?
>
> > I plan to extend the KSYMBOL interface to contain trampolines/dispatcher
> > data,
>
> That seems like the sensible, without looking too much at all the
> details, to do, yes.
>
> > plus we could do some inteligent fallback to /proc/kallsyms in case
> > vmlinux won't have anything
>
> At this point what would be the good reason to prefer vmlinux instead of
> going straight to using /proc/kallsyms?
symbol (with sizes) and code for dwarf unwind, processor trace
jirka
>
> We have support for taking a snapshot of it at 'perf top' start, i.e.
> right at the point we need to resolve a kernel symbol, then we get
> PERF_RECORD_KSYMBOL for things that gets in place after that.
>
> And as well we save it to the build-id cache so that later, at 'perf
> report/script' time we can resolve kernel symbols, etc.
>
> vmlinux is just what is in there right before boot, after that, for
> quite some time, _lots_ of stuff happens :-)
>
> - Arnaldo
>
next prev parent reply other threads:[~2020-02-12 22:40 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-08 15:41 [PATCH 00/14] bpf: Add trampoline and dispatcher to /proc/kallsyms Jiri Olsa
2020-02-08 15:41 ` [PATCH 01/14] x86/mm: Rename is_kernel_text to __is_kernel_text Jiri Olsa
2020-02-08 15:41 ` [PATCH 02/14] bpf: Add bpf_trampoline_ name prefix for DECLARE_BPF_DISPATCHER Jiri Olsa
2020-02-08 15:41 ` [PATCH 03/14] bpf: Add struct bpf_ksym Jiri Olsa
2020-02-08 15:41 ` [PATCH 04/14] bpf: Add name to " Jiri Olsa
2020-02-08 15:42 ` [PATCH 05/14] bpf: Add lnode list node " Jiri Olsa
2020-02-08 15:42 ` [PATCH 06/14] bpf: Add bpf_kallsyms_tree tree Jiri Olsa
2020-02-11 18:21 ` Andrii Nakryiko
2020-02-12 10:49 ` Jiri Olsa
2020-02-08 15:42 ` [PATCH 07/14] bpf: Move bpf_tree add/del from bpf_prog_ksym_node_add/del Jiri Olsa
2020-02-08 15:42 ` [PATCH 08/14] bpf: Separate kallsyms add/del functions Jiri Olsa
2020-02-08 15:42 ` [PATCH 09/14] bpf: Add bpf_ksym_add/del functions Jiri Olsa
2020-02-08 15:42 ` [PATCH 10/14] bpf: Re-initialize lnode in bpf_ksym_del Jiri Olsa
2020-02-11 18:28 ` Andrii Nakryiko
2020-02-12 10:43 ` Jiri Olsa
2020-02-08 15:42 ` [PATCH 11/14] bpf: Rename bpf_tree to bpf_progs_tree Jiri Olsa
2020-02-08 15:42 ` [PATCH 12/14] bpf: Add trampolines to kallsyms Jiri Olsa
2020-02-11 18:51 ` Andrii Nakryiko
2020-02-12 11:10 ` Jiri Olsa
2020-02-12 16:33 ` Andrii Nakryiko
2020-02-12 22:58 ` Jiri Olsa
2020-02-12 23:02 ` Jiri Olsa
2020-02-08 15:42 ` [PATCH 13/14] bpf: Add dispatchers " Jiri Olsa
2020-02-11 19:03 ` Andrii Nakryiko
2020-02-12 10:52 ` Jiri Olsa
2020-02-08 15:42 ` [PATCH 14/14] bpf: Sort bpf kallsyms symbols Jiri Olsa
2020-02-11 19:12 ` Andrii Nakryiko
2020-02-10 15:51 ` [PATCH 00/14] bpf: Add trampoline and dispatcher to /proc/kallsyms Björn Töpel
2020-02-10 16:17 ` Jiri Olsa
2020-02-11 19:32 ` Arnaldo Carvalho de Melo
2020-02-12 11:13 ` Jiri Olsa
2020-02-12 13:31 ` Arnaldo Carvalho de Melo
2020-02-12 22:40 ` Jiri Olsa [this message]
2020-02-13 16:23 ` Jiri Olsa
2020-02-11 19:13 ` Arnaldo Carvalho de Melo
2020-02-12 10:46 ` Jiri Olsa
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