All of lore.kernel.org
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	Nadav Amit <nadav.amit@gmail.com>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Song Liu <songliubraving@fb.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH 3/3] x86/ftrace: Use text_poke()
Date: Mon, 7 Oct 2019 10:08:47 +0200	[thread overview]
Message-ID: <20191007080847.GB2311@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <7b4196a4-b6e1-7e55-c3e1-a02d97c262c7@redhat.com>

On Fri, Oct 04, 2019 at 10:10:47AM +0200, Daniel Bristot de Oliveira wrote:
> 1) the enabling/disabling ftrace path
> 2) the int3 path - if a thread/irq is running a kernel function
> 3) the IPI - that affects all CPUs, even those that are not "hitting" trace
> code, e.g., user-space.
> 
> The first one is for sure a cold-path. The second one is a hot-path: any task
> running kernel functions will hit it. But IMHO, the hottest one is the IPIs,
> because it will run on all CPUs, e.g., even isolated CPUs that are running in
> user-space.

Well, we can fix that, just like RCU. In fact, I suspect RCU has all the
bits required to cure this.

For NOHZ_FULL CPUs you can forgo the IPI and delay it until the next kernel
entry, just like RCU.

  parent reply	other threads:[~2019-10-07  8:09 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-27 18:06 [PATCH 0/3] Rewrite x86/ftrace to use text_poke() Peter Zijlstra
2019-08-27 18:06 ` [PATCH 1/3] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-10-03  5:00   ` Masami Hiramatsu
2019-10-03  8:27     ` Peter Zijlstra
2019-10-03 11:01       ` Peter Zijlstra
2019-10-03 12:32         ` Peter Zijlstra
2019-10-04 13:45         ` Masami Hiramatsu
2019-10-07  8:05           ` Peter Zijlstra
2019-10-09 13:07           ` x86/kprobes bug? (was: [PATCH 1/3] x86/alternatives: Teach text_poke_bp() to emulate instructions) Peter Zijlstra
2019-10-09 13:26             ` Peter Zijlstra
2019-10-09 13:28               ` Peter Zijlstra
2019-10-09 14:26             ` Mathieu Desnoyers
2019-10-17 19:59               ` Peter Zijlstra
2019-10-03 13:05       ` [PATCH 1/3] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-08-27 18:06 ` [PATCH 2/3] x86/alternatives,jump_label: Provide better text_poke() batching interface Peter Zijlstra
2019-10-02 16:34   ` Daniel Bristot de Oliveira
2019-10-03  5:50   ` Masami Hiramatsu
2019-08-27 18:06 ` [PATCH 3/3] x86/ftrace: Use text_poke() Peter Zijlstra
2019-10-02 16:35   ` Daniel Bristot de Oliveira
2019-10-02 18:21     ` Peter Zijlstra
2019-10-03 22:10       ` Steven Rostedt
2019-10-04  8:10         ` Daniel Bristot de Oliveira
2019-10-04 13:40           ` Steven Rostedt
2019-10-04 14:44             ` Daniel Bristot de Oliveira
2019-10-04 15:13               ` Steven Rostedt
2019-10-07  8:08           ` Peter Zijlstra [this message]
2019-10-11  7:01           ` Peter Zijlstra
2019-10-11  7:37             ` Daniel Bristot de Oliveira
2019-10-11 10:57               ` Peter Zijlstra
2019-10-11 13:11               ` Steven Rostedt
2019-10-04 11:22         ` Peter Zijlstra
2019-10-04 13:42           ` Steven Rostedt
2019-10-22  0:36             ` Alexei Starovoitov
2019-10-22  0:43               ` Steven Rostedt
2019-10-22  3:10                 ` Alexei Starovoitov
2019-10-22  3:16                   ` Steven Rostedt
2019-10-22  3:19                     ` Steven Rostedt
2019-10-22  4:05                       ` Alexei Starovoitov
2019-10-22 11:19                         ` Steven Rostedt
2019-10-22 13:44                           ` Steven Rostedt
2019-10-22 17:50                             ` Alexei Starovoitov
2019-10-22 18:10                               ` Steven Rostedt
2019-10-22 20:46                                 ` Alexei Starovoitov
2019-10-22 21:04                                   ` Steven Rostedt
2019-10-22 21:58                                     ` Alexei Starovoitov
2019-10-22 22:17                                       ` Steven Rostedt
2019-10-23  2:02                                         ` Steven Rostedt
2019-10-22 22:45                                       ` Andy Lutomirski
2019-10-22 23:21                                         ` Steven Rostedt
2019-10-22 23:49                                         ` Alexei Starovoitov
2019-10-23  4:20                                           ` Andy Lutomirski
2019-10-23  9:02                                             ` Peter Zijlstra
2019-10-23 16:23                                       ` Steven Rostedt
2019-10-23 17:42                                         ` Steven Rostedt
2019-10-23 19:34                                         ` Alexei Starovoitov
2019-10-23 20:08                                           ` Steven Rostedt
2019-10-23 22:36                                             ` Alexei Starovoitov
2019-10-22  3:55                     ` Alexei Starovoitov
2019-10-03  5:52     ` Masami Hiramatsu
2019-08-28  7:22 ` [PATCH 0/3] Rewrite x86/ftrace to use text_poke() Song Liu

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=20191007080847.GB2311@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=bristot@redhat.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=mhiramat@kernel.org \
    --cc=nadav.amit@gmail.com \
    --cc=rostedt@goodmis.org \
    --cc=songliubraving@fb.com \
    --cc=x86@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
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.