Subject: Re: [PATCH v3 1/5] perf_event: introduce 'inject' event and get HZ
From: Peter Zijlstra <peterz@infradead.org>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, 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>
In-Reply-To: <4B3B1F3C.8010509@cn.fujitsu.com>
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Date: Wed, 30 Dec 2009 10:45:57 +0100
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On Wed, 2009-12-30 at 17:37 +0800, Xiao Guangrong wrote:
> > 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.
> > 
> 
> Yes, it like write and it writes something form kernel to perf.
> And, i think this name is suitable for it's doing that injects an
> 'artificial' event, it's well if you have other name for it :-)

No, what I means is that you cannot actually inject an arbitrary event.
Sure it injects something, but that's pretty limited.

> > This just seems like a very weird way of getting data out. A kind of
> > like sysconf() but done very strange.
> > 
> 
> It's since some parameter is only used by perf, suce as HZ in this patch and
> 'relocation offset' in my other patchset, it also well if has better way to
> do it :-)

The thing is, this proposed interface is very much tied to perf and
makes it basically impossible for !perf to use. Whereas I can imagine
esp. the relocation offset to be interesting for other things. Basically
everything needing to resolve a kernel symbol.


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