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Date: Fri, 26 Sep 2008 06:45:28 -0400 (EDT)
From: Steven Rostedt <rostedt@goodmis.org>
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To: Peter Zijlstra <peterz@infradead.org>
cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>,
       Masami Hiramatsu <mhiramat@redhat.com>,
       LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>,
       Andrew Morton <akpm@linux-foundation.org>, prasad@linux.vnet.ibm.com,
       Linus Torvalds <torvalds@linux-foundation.org>,
       "Frank Ch. Eigler" <fche@redhat.com>, David Wilder <dwilder@us.ibm.com>,
       hch@lst.de, Martin Bligh <mbligh@google.com>,
       Christoph Hellwig <hch@infradead.org>,
       Steven Rostedt <srostedt@redhat.com>
Subject: Re: [RFC PATCH v4] Unified trace buffer
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On Fri, 26 Sep 2008, Peter Zijlstra wrote:
> On Thu, 2008-09-25 at 23:20 -0400, Mathieu Desnoyers wrote:
> > 
> > You could also fallback on a 2-level page array when buffer size is >
> > 64MB. The cost is mainly a supplementary pointer dereference, but one
> > more should not make sure a big difference overall.
> 
> I'm still not sure why we don't just link the pages using the page
> frames, we don't need the random access, do we?

Yeah we can go back to that (as ftrace does).

1) It can be very error prone. I will need to encapsulate the logic more.

2) I'm still not sure if crash can handle it.


I was going to reply to Masami with this answer, but it makes things more 
complex.  For v1 (non RFC v1) I wanted to start simple. v2 can have this 
enhancement.

-- Steve