Message-ID: <50359CE9.3000509@hitachi.com>
Date: Thu, 23 Aug 2012 12:00:57 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Organization: Hitachi, Ltd., Japan
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To: Steven Rostedt <rostedt@goodmis.org>
Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>,
        Amit Shah <amit.shah@redhat.com>,
        Anthony Liguori <anthony@codemonkey.ws>, Arnd Bergmann <arnd@arndb.de>,
        Borislav Petkov <bp@amd64.org>, "Franch Ch. Eigler" <fche@redhat.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.hengli.com.au>,
        Ingo Molnar <mingo@redhat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Rusty Russell <rusty@rustcorp.com.au>, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org,
        yrl.pp-manager.tt@hitachi.com
Subject: Re: [PATCH 2/5] trace-cmd: Use tracing directory to count CPUs
References: <20120822084251.17293.69086.stgit@ltc189.sdl.hitachi.co.jp>  <20120822084312.17293.47596.stgit@ltc189.sdl.hitachi.co.jp> <1345642893.5069.31.camel@gandalf.local.home> <50358F13.1030607@hitachi.com>
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(2012/08/23 11:01), Masami Hiramatsu wrote:
> (2012/08/22 22:41), Steven Rostedt wrote:
>> On Wed, 2012-08-22 at 17:43 +0900, Yoshihiro YUNOMAE wrote:
>>> From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>>>
>>> Count debugfs/tracing/per_cpu/cpu* to determine the
>>> number of CPUs.
>>
>> I'm curious, do you find that sysconf doesn't return the # of CPUs the
>> system has?
> 
> No, sysconf returns the number of hosts CPUs, not guests.
> 
>> I've had boxes where the per_cpu/cpu* had more cpus than the
>> box actually holds. But this was a bug in the kernel, not the tool. This
>> change log needs to have rational instead of just explaining what the
>> patch does.
> 
> Ah, I see. Hmm, then this should be enabled by a command line
> option or an environment variable.

Oops, I misunderstood. I'll add more comment for why this
should be tried instead of sysconf.

Thank you,
-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com


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