BPF Archive on lore.kernel.org
 help / color / Atom feed
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
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
> 


  reply index

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-08 15:41 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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200212224039.GA233036@krava \
    --to=jolsa@redhat.com \
    --cc=andriin@fb.com \
    --cc=arnaldo.melo@gmail.com \
    --cc=ast@kernel.org \
    --cc=bjorn.topel@gmail.com \
    --cc=bjorn.topel@intel.com \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@redhat.com \
    --cc=hawk@kernel.org \
    --cc=john.fastabend@gmail.com \
    --cc=jolsa@kernel.org \
    --cc=kafai@fb.com \
    --cc=kuba@kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=songliubraving@fb.com \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

BPF Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/bpf/0 bpf/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 bpf bpf/ https://lore.kernel.org/bpf \
		bpf@vger.kernel.org
	public-inbox-index bpf

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.bpf


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git