From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4B68A2C0F81; Fri, 30 Jan 2026 13:24:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769779492; cv=none; b=EbB5QpWuGDKi3eIpptRilcs0+aJwD2aA0gm8gqLyP6IbsPt78joHsrecTJPbnKAQlD0LtSePHq2tULI2bNGgB7hVSj3G3H9mPyRMdly7RABIvc9JjSahKrO9t5hYm5hcqjYtOaFArxuRR4gK7JO8zlpYP0Zb42A/nsRzVDKh+Ss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769779492; c=relaxed/simple; bh=/0GtwHky32P8HvYvPanrDvkBOq9l3/DB6LEAYqcFGlk=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=I6DtwLuv2oYhMRfyXMFVbs5PDe5Mttqtfyqx7oKIkRMqPxJUZMsEYl+TOYVfkH0m80shquaisVZzxcZVOSoQVMuey0bnoXbawpWPs56HTDLWK82woPd2V4kggWzdQvUkb28IJCOjc/9ixN92IXRp7CTWyFzFpMNB8IkRZsWOI+c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=uJcnfgGC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="uJcnfgGC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1220BC4CEF7; Fri, 30 Jan 2026 13:24:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769779491; bh=/0GtwHky32P8HvYvPanrDvkBOq9l3/DB6LEAYqcFGlk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=uJcnfgGCUDaQoD4ouUp/F0R3mbsmg15TjnUeDvwug9MmOHC1o8SwhsCv+0JWcGSGa VKBhyBmoMQtxIbl8A2GAjWit7ADNuHbKO8NLspvxIH7uuRl80XqkS8m/IcGOPkNPS4 AWvBd2lNg3h4ehDdsDY/JXneDi1WPiwHazSPWgRhLb3/7mEC9JqHc8sdBE06FLr3J9 /nn9Jg+gRc3qtRcvkZ0TkpuLwI3O0h9bEEpTn0fPxLWAHb027njWoDi84BG2rnp4U3 5a1edMrCKmsw+IzK0r/E7Z/BC4C+694kDQMU5vI52qwrxO1SdYhIpsfVwK/uTrOw27 C7wtn2slbLL4A== Date: Fri, 30 Jan 2026 22:24:49 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt 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: <20260130222449.bc25b973597721b6a22e4f6d@kernel.org> In-Reply-To: <20260129151900.44b6182c@gandalf.local.home> References: <176955897718.2786091.11948759407196200082.stgit@mhiramat.tok.corp.google.com> <176955901173.2786091.7719483008240216705.stgit@mhiramat.tok.corp.google.com> <20260129151900.44b6182c@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (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 On Thu, 29 Jan 2026 15:19:00 -0500 Steven Rostedt wrote: > 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" Ah, thanks, > > > +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 ^ the "boot_map". > > Thus the user > > > +without stopping trace. > > stopping the trace. OK. > > > + > > +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 ;-) Thanks! > > -- Steve -- Masami Hiramatsu (Google)