linux-kernel - Re: ivring driver

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Date:	Tue, 12 Jun 2012 11:36:57 +0900
From:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	linux-kernel@...r.kernel.org,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: ivring driver

(2012/06/06 0:29), Mathieu Desnoyers wrote:
> Hi Yoshihiro,
>
> I stumbled on your post on ivring (https://lkml.org/lkml/2012/6/5/143)
> for buffering trace data from guest to host. I notice that it would be
> very interesting to see a comparison of its performance against:
>
> - ftrace ring buffer
> - perf ring buffer
> - lttng 2.0 ring buffer
> - lttng-ust 2.0 (user-space tracing) ring buffer

Hi Mathieu. Thank you for commenting on how to compare among
ring-buffer's performances. And sorry, I'm late for replying to you.

> Comparing only with network-related mechanisms does not seem to provide
> a complete picture of where it stands wrt other ring buffers out there.
>
> One of the metric we have used in the past is the number of nanoseconds
> it takes to write a single event, based on a test that writes lots of
> events into various buffer sizes, into flight recorder mode buffers
> (which overwrites oldest information on buffer full condition, with data
> collection to disk disabled, to remove I/O from the picture -- I/O can
> then be performed in "snapshot" mode, after some error condition is
> detected).

OK, I see. When the overhead of ring-buffers will be evaluated in
the next, I may use the metric as a reference.

Thank you,

-- 
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@...achi.com
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