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Date: Fri, 26 Sep 2008 12:46:23 -0700
From: "Martin Bligh" <mbligh@google.com>
To: "Peter Zijlstra" <peterz@infradead.org>
Subject: Re: [PATCH v6] Unified trace buffer
Cc: "Steven Rostedt" <rostedt@goodmis.org>,
       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>,
       "Mathieu Desnoyers" <compudj@krystal.dyndns.org>,
       "Frank Ch. Eigler" <fche@redhat.com>,
       "David Wilder" <dwilder@us.ibm.com>, hch@lst.de,
       "Christoph Hellwig" <hch@infradead.org>,
       "Masami Hiramatsu" <mhiramat@redhat.com>,
       "Steven Rostedt" <srostedt@redhat.com>,
       "Arnaldo Carvalho de Melo" <acme@ghostprotocols.net>
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On Fri, Sep 26, 2008 at 11:59 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, 2008-09-26 at 14:05 -0400, Steven Rostedt wrote:
>
>> +struct buffer_page {
>> +     u64             time_stamp;
>> +     unsigned char   body[];
>> +};
>> +
>> +#define BUF_PAGE_SIZE (PAGE_SIZE - sizeof(u64))
>
> Since you're already using the page frame, you can stick this per page
> timestamp in there as well, and get the full page for data.
>
> You can either use a struct page overlay like slob does, or add a u64 in
> the union that contains struct {private, mapping}.

What did you guys think of Mathieu's idea of sticking the buffer length
in the header here, rather than using padding events? Seemed cleaner
to me.