From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12911218ADD; Thu, 29 Jan 2026 20:18:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769717932; cv=none; b=ae23oFEfEncWhdyo1VyckX+sRjrtizMUd87LhpDx6yWh81Fwf5vW1O5Fb/FhkfkJ/L6pACqpgBzayZt311HnoRgeCSe4zsScGKzKENr13vvuiCjuWEPNMS30FrkOzJy76oipc4nRmel9OxMg4A2lkquzelqlgrHD7omGAiji94w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769717932; c=relaxed/simple; bh=e4yfknTmyw95fHxVG+8zTb4mbzHsH3w+zAo8geKXDmw=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=IdqFo1tukUeYpsIwpsUht7vrQVpE8zbhdLIbrvKdgzFFjv3icPf3Qm3tEbVkALSq4oVk+BDgupZZ2zm9IEUteQ6GWHdGfvoD3jzankpLsf9S3Ps338BHOCB7XU8LyJeNu/AF4ojyJ+PPXu21dg6i+u//3IJOdElRBKtRKsvMqr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id F1900B7E8C; Thu, 29 Jan 2026 20:18:49 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf19.hostedemail.com (Postfix) with ESMTPA id 6962220029; Thu, 29 Jan 2026 20:18:48 +0000 (UTC) Date: Thu, 29 Jan 2026 15:19:00 -0500 From: Steven Rostedt To: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v5 4/4] tracing/Documentation: Add a section about backup instance Message-ID: <20260129151900.44b6182c@gandalf.local.home> In-Reply-To: <176955901173.2786091.7719483008240216705.stgit@mhiramat.tok.corp.google.com> References: <176955897718.2786091.11948759407196200082.stgit@mhiramat.tok.corp.google.com> <176955901173.2786091.7719483008240216705.stgit@mhiramat.tok.corp.google.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: 8jf4t6s6qfqzsmxy4q1ag3n34dnhjw8a X-Rspamd-Server: rspamout04 X-Rspamd-Queue-Id: 6962220029 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+A7moSVfg9urlwMoNrnEGHscSXt6ClBbw= X-HE-Tag: 1769717928-445420 X-HE-Meta: U2FsdGVkX18VvbGH6zeo7IM/SlTneLa8/o5K1oXychGCPiBJ5guAiKidsLvkzl/KebgTfiqPgPBVkiTqANCE5fX9+58Wtx/KeZBjdBrzWgv8fPZlYm9VA8SjZDNy7z7Oft/xjhSGkaopNXJ24g/3VYO9Rp3pQd6hsYo4aRdj3ktKqlTs94iH4gDIUPqnoPOJt9540fV/3CpmVF55+8HrHUdgE63XbviD4s6FDaCvFdAiE5SN+Ez/CbVFgJ6Lu1feJ+lGDCwoRQdfPJLA4jvC1VNg02LnZBQsAItwvL66wWPVk7NsnXf8Jn03Owu7Kr33v2YzRVd5/TYzcdnm9bcJwV0Ezh9BKNuu On Wed, 28 Jan 2026 09:10:11 +0900 "Masami Hiramatsu (Google)" wrote: > From: Masami Hiramatsu (Google) > > Add a section about backup instance to the debugging.rst. > > Signed-off-by: Masami Hiramatsu (Google) > --- > Documentation/trace/debugging.rst | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/Documentation/trace/debugging.rst b/Documentation/trace/debugging.rst > index 4d88c346fc38..73e2154bcf98 100644 > --- a/Documentation/trace/debugging.rst > +++ b/Documentation/trace/debugging.rst > @@ -159,3 +159,22 @@ If setting it from the kernel command line, it is recommended to also > disable tracing with the "traceoff" flag, and enable tracing after boot up. > Otherwise the trace from the most recent boot will be mixed with the trace > from the previous boot, and may make it confusing to read. > + > +Using a backup instance for keeping previous boot data > +------------------------------------------------------ > + > +It is also possible to record trace data at system boot time by specifying > +events with the persistent ring buffer, but in this case the data before the > +reboot will be lost before it can be read. This problem can be solved by a > +backup instance. From the kernel command line:: > + > + reserve_mem=12M:4096:trace trace_instance=boot_map@trace,sched,irq trace_instance=backup=boot_map > + > +When the boot up, the previous data in the`boot_map` is copied to "backup" s/When the boot up/On boot up/ copied to the "backup" > +instance, and the "sched:*" and "irq:*" events for current boot are traced on for the current boot are traced in > +"boot_map". Thus user can read the previous boot data from the "backup" instance Thus the user > +without stopping trace. stopping the trace. > + > +Note that this "backup" instance is readonly, and will be removed automatically > +if you clear the trace data or read out all trace data from "trace_pipe" or > +"trace_pipe_raw" files. > \ No newline at end of file Definite articles are a pain ;-) -- Steve