From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [patch 4/4] KVM-trace port to tracepoints
Date: Wed, 23 Jul 2008 06:13:10 -0400
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Cc: Christoph Hellwig <hch@infradead.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Jan Kiszka <jan.kiszka@siemens.com>,
	Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
	akpm@linux-foundation.org, Ingo Molnar <mingo@elte.hu>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	"Feng(Eric) Liu" <eric.e.liu@intel.com>
To: Avi Kivity <avi@qumranet.com>
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On Wed, Jul 23, 2008 at 01:08:41PM +0300, Avi Kivity wrote:
> trace_mark() is implement kvmtrace, which is propagated to userspace.   
> So while trace_mark() itself is not a userspace interface, one of its  
> users is.
>
> It's an unstable interface.  But so is dmesg; that's the nature of tracing.

Trace_mark is as stable as any other kernel interface, and
the data you pass through it is as stable as you want it to.  In most
cases like kvmtrace or my spu scheduler tracing code the trace data
is directly forwarded through a userspace interface, and that is as
stable as any freeform interface, e.g. as like printk mentioned above.