BPF Archive on lore.kernel.org
 help / color / Atom feed
From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
	Daniel Borkmann <daniel@iogearbox.net>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	"David S . Miller" <davem@davemloft.net>,
	paulmck@kernel.org, joel@joelfernandes.org,
	"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Subject: Re: [RFT PATCH 04/13] kprobes: Make optimizer delay to 1 second
Date: Wed, 22 Jan 2020 07:11:15 -0500
Message-ID: <20200122071115.28e3c763@gandalf.local.home> (raw)
In-Reply-To: <20200122162317.0299cf722dd618147d97e89c@kernel.org>

On Wed, 22 Jan 2020 16:23:17 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> On Tue, 21 Jan 2020 19:29:05 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> > On Thu, 16 Jan 2020 23:44:52 +0900
> > Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >   
> > > Since the 5 jiffies delay for the optimizer is too
> > > short to wait for other probes, make it longer,
> > > like 1 second.  
> > 
> > Hi Masami,
> > 
> > Can you explain more *why* 5 jiffies is too short.  
> 
> Yes, I had introduced this 5 jiffies delay for multiple probe registration
> and unregistration like systemtap, which will use array-based interface to
> register/unregister. In that case, 5 jiffies will be enough for the delay
> to wait for other kprobe registration/unregsitration.
> 
> However, since perf and ftrace register/unregister probes one-by-one with
> RCU synchronization interval, the optimizer will be started before
> finishing to register/unregister all probes.
> And the optimizer locks kprobe_mutex a while -- RCU-tasks synchronization.
> Since the kprobe_mutex is also involved in disabling kprobes, this also
> stops probe-event disabling.
> 
> Maybe 5 jiffies is enough for adding/removing a few probe events, but
> not enough for dozens of probe events.
> 

Perhaps we should have a mechanism that can detect new probes being
added, and just continue to delay the optimization, instead of having
some arbitrary delay.

-- Steve

  reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 14:44 [RFT PATCH 00/13] tracing: kprobes: Introduce async unregistration Masami Hiramatsu
2020-01-16 14:44 ` [RFT PATCH 01/13] kprobes: Fix to protect kick_kprobe_optimizer() by kprobe_mutex Masami Hiramatsu
2020-01-16 14:44 ` [RFT PATCH 02/13] kprobes: Remove redundant arch_disarm_kprobe() call Masami Hiramatsu
2020-01-16 14:44 ` [RFT PATCH 03/13] kprobes: Postpone optimizer until a bunch of probes (un)registered Masami Hiramatsu
2020-01-16 14:44 ` [RFT PATCH 04/13] kprobes: Make optimizer delay to 1 second Masami Hiramatsu
2020-01-22  0:29   ` Steven Rostedt
2020-01-22  7:23     ` Masami Hiramatsu
2020-01-22 12:11       ` Steven Rostedt [this message]
2020-01-22 13:12         ` Masami Hiramatsu
2020-01-22 16:54           ` Paul E. McKenney
2020-01-23  1:33             ` Masami Hiramatsu
2020-01-23  2:26               ` Paul E. McKenney
2020-01-23  6:13                 ` Masami Hiramatsu
2020-01-23 10:03                   ` Paul E. McKenney
2020-01-16 14:45 ` [RFT PATCH 05/13] tracing/kprobe: Use call_rcu to defer freeing event_file_link Masami Hiramatsu
2020-01-27 15:02   ` kbuild test robot
2020-01-27 15:02   ` [RFC PATCH] tracing/kprobe: trace_kprobe_disabled_finished can be static kbuild test robot
2020-01-28 15:02     ` Masami Hiramatsu
2020-01-16 14:45 ` [RFT PATCH 06/13] kprobes: Enable kprobe-booster with CONFIG_PREEMPT=y Masami Hiramatsu
2020-01-16 14:45 ` [RFT PATCH 07/13] kprobes: Use normal list traversal API if a mutex is held Masami Hiramatsu
2020-01-16 14:45 ` [RFT PATCH 08/13] kprobes: Use workqueue for reclaiming kprobe insn cache pages Masami Hiramatsu
2020-01-16 14:45 ` [RFT PATCH 09/13] kprobes: Free kprobe_insn_page asynchronously Masami Hiramatsu
2020-01-16 14:45 ` [RFT PATCH 10/13] kprobes: Make free_*insn_slot() mutex-less Masami Hiramatsu
2020-01-16 14:46 ` [RFT PATCH 11/13] kprobes: Add asynchronous unregistration APIs Masami Hiramatsu
2020-01-16 14:46 ` [RFT PATCH 12/13] tracing/kprobe: Free probe event asynchronously Masami Hiramatsu
2020-01-16 14:46 ` [RFT PATCH 13/13] tracing/kprobe: perf_event: Remove local kprobe " Masami Hiramatsu

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=20200122071115.28e3c763@gandalf.local.home \
    --to=rostedt@goodmis.org \
    --cc=acme@kernel.org \
    --cc=anil.s.keshavamurthy@intel.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=brendan.d.gregg@gmail.com \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=joel@joelfernandes.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mhiramat@kernel.org \
    --cc=mingo@kernel.org \
    --cc=naveen.n.rao@linux.ibm.com \
    --cc=paulmck@kernel.org \
    /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