Date: Wed, 30 Dec 2009 10:44:17 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Thomas Gleixner <tglx@linutronix.de>,
       Steven Rostedt <rostedt@goodmis.org>, Paul Mackerras <paulus@samba.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 1/5] perf_event: introduce 'inject' event and get HZ
Message-ID: <20091230094417.GC18190@elte.hu>
References: <4B27702F.1080507@cn.fujitsu.com>
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 <4B30C3A0.909@cn.fujitsu.com>
 <20091228075417.GB20039@elte.hu>
 <4B3991C1.6060303@cn.fujitsu.com>
 <1262164786.7135.166.camel@laptop>
 <20091230092830.GA18190@elte.hu>
 <1262165789.7135.170.camel@laptop>
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, 2009-12-30 at 10:28 +0100, Ingo Molnar wrote:
> > * Peter Zijlstra <peterz@infradead.org> wrote:
> > 
> > > On Tue, 2009-12-29 at 13:21 +0800, Xiao Guangrong wrote:
> > > > 'inject' event is a very useful feature and it's suggested by Ingo
> > > > [ See http://lkml.org/lkml/2009/12/28/31 ]
> > > 
> > > I really dislike the name, event injection to me would be like a write() 
> > > interface where you provide the actual event data to be stuffed in the 
> > > output stream.
> > > 
> > > This just seems like a very weird way of getting data out. A kind of like 
> > > sysconf() but done very strange.
> > 
> > What kind of API would you suggest?
> 
> sysconf() seems ideal for getting single, mostly constant variables out
> of the kernel, we already have non POSIX (read Linux specific) names in
> there.
> 
> _SC_KERNEL_RELOCATION_OFFSET
> _SC_KERNEL_HZ
> 
> or somethings like that comes to mind.

Nah. HZ might be static here but we'll have more dynamic parameters so the 
sysconf API is rather inflexible there.

I was thinking of something that fits into existing perf API schemes, to keep 
it simple and self-sufficient, and to allow for extensions/etc.

	Ingo
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