Re: [RFC PATCH 1/2 v2] Unified trace buffer

Linus Torvalds
2008-09-25T17:32:26Z

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