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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: Tue, 23 Sep 2008 23:36:26 +0900 (JST)
- Subject: Re: Unified tracing buffer
- References: <33307c790809221313s3532d851g7239c212bc72fe71@mail.gmail.com> <48D81B5F.2030702@redhat.com>
> By the way, systemtap uses two modes;
>
> - single-channel mode
> In this mode, all cpus share one buffer channel to write and read.
> each writer locks spinlock and write a probe-local data to buffer.
>
> - per-cpu buffer mode
> In this mode, we use an atomic sequential number for ordering data. If
> user doesn't need it(because they have their own timestamps), they can
> choose not to use that seq-number.
I can't imazine a merit of the single-channel mode.
Could you please explain it?
Because some architecture don't have fine grained timestamp?
if so, could you explain which architecture don't have it?