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Re: Unified tracing buffer
- From: KOSAKI Motohiro <kosaki dot motohiro at jp dot fujitsu dot com>
- To: Masami Hiramatsu <mhiramat at redhat dot com>
- Cc: kosaki dot motohiro at jp dot fujitsu dot com, Martin Bligh <mbligh at google dot com>, Linux Kernel Mailing List <linux-kernel at vger dot kernel dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Thomas Gleixner <tglx at linutronix dot de>, Mathieu Desnoyers <compudj at krystal dot dyndns dot org>, Steven Rostedt <rostedt at goodmis dot org>, od at novell dot com, "Frank Ch. Eigler" <fche at redhat dot com>, systemtap-ml <systemtap at sources dot redhat dot com>
- Date: Wed, 24 Sep 2008 02:59:37 +0900 (JST)
- Subject: Re: Unified tracing buffer
- References: <20080923232239.DC1E.KOSAKI.MOTOHIRO@jp.fujitsu.com> <48D90970.3060409@redhat.com>
> > I can't imazine a merit of the single-channel mode.
> > Could you please explain it?
>
> Actually, single-channel mode is for not-frequently event tracing.
> At least systemtap case, sometimes we just want to collect data
> and watch it periodically(as like as 'top'). Or, just monitoring
> errors as additional printk. in these cases, overhead is not so
> important.
>
> I think the main reason of using single-channel mode is simplicity of
> userspace reader. We can use 'cat' or 'tail' to read the buffer on-line.
> I'm not sure how much overhead ftrace-like buffer merging routine has,
> but if kernel provides an interface which gives us single-merged buffer
> image(like ftrace buffer), we are grad to use it. :-)
Yup, I also think it is better.
Thanks.