From: Linus Torvalds <torvalds@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
prasad@linux.vnet.ibm.com,
Mathieu Desnoyers <compudj@krystal.dyndns.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 1/2 v2] Unified trace buffer
Date: Thu, 25 Sep 2008 10:25:00 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.1.10.0809251023090.3265@nehalem.linux-foundation.org> (raw)
In-Reply-To: <alpine.DEB.1.10.0809251312010.27920@gandalf.stny.rr.com>
On Thu, 25 Sep 2008, Steven Rostedt wrote:
>
> The problem with this is overwrite mode, which is the only mode ftace
> currently offers. What happens when your writer starts overwriting the
> ring buffer and there is no reader?
Overwrite things on page at a time. Don't you already do that? (I didn't
check that closely, I just assumed you would do the _much_ simpler "move
the head to the next page" thing rather than trying to mix head and tail
on the same page.
> What happens is that the start value is gone. You do not have a way to use
> all the deltas to catch up to the remaining events.
Use the page start date for the first event in a page. But within pages,
make everything depend on previous event.
Linus
next prev parent reply other threads:[~2008-09-25 17:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-25 15:58 [RFC PATCH 0/2 v2] Unified trace buffer (take two) Steven Rostedt
2008-09-25 15:58 ` [RFC PATCH 1/2 v2] Unified trace buffer Steven Rostedt
2008-09-25 17:02 ` Linus Torvalds
2008-09-25 17:16 ` Steven Rostedt
2008-09-25 17:25 ` Linus Torvalds [this message]
2008-09-25 17:46 ` Steven Rostedt
2008-09-25 17:35 ` Mathieu Desnoyers
2008-09-25 17:48 ` Steven Rostedt
2008-09-25 18:25 ` Mathieu Desnoyers
2008-09-25 15:58 ` [RFC PATCH 2/2 v2] ftrace: make work with new ring buffer Steven Rostedt
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