linux-kernel - Re: [PATCH] printk: add KERN_NOTIME to skip the timestamp

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Message-ID: <20190213080852.GA1702@jagdpanzerIV>
Date:   Wed, 13 Feb 2019 17:08:52 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     xiang xiao <xiaoxiang781216@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, Xiang Xiao <xiaoxiang@...omi.com>
Subject: Re: [PATCH] printk: add KERN_NOTIME to skip the timestamp

On (02/13/19 15:14), xiang xiao wrote:
>
> But how can I precisely control timestamp on/off per message
> through sysfs node?
>

Hmm. I don't know how many kernel printk-s you have and how often
do you write to kmsg. I was thinking about something like this:

	echo 0 > /...printk.../time
	dump buffer to /dev/kmsg
	echo 1 > /...printk../time

- If you would have several kernel printk-s in the meantime, then
  those would not have timestamps, but you kinda can roughly guess
  it

	write [1243] foo > /dev/kmsg
	write [1244] foo > /dev/kmsg
		<< printk(bar)               <timestamp ~[1244,1245]>
	write [1245] foo > /dev/kmsg

Maybe this won't suffice.

	-ss