Re: [RFC PATCH 1/3] Unified trace buffer
From: Linus Torvalds
Date: Thu Sep 25 2008 - 13:32:08 EST
On Thu, 25 Sep 2008, Mathieu Desnoyers wrote:
>
> We could use a page header instead to contain the "unused_size"
> information.
Absolutely. There's no one way to do this.
> I would prefer to put the extended timestamp within the event header
> instead of creating a separate entry for this for atomicity concerns
> (what happens if a long interrupt executes between the TSCExtend marker
> event and the event expecting to be written right next to it ?).
The log entries should be reserved with interrupts disabled anyway, and
they are per-CPU, so there are no atomicity issues.
For NMI's, things get more exciting. I'd really prefer NMI's to go to a
separate ring buffer entirely, because otherwise consistency gets really
hard. Using lockless algorithms for a variable-sized pool of pages is a
disaster waiting to happen.
I don't think we can currently necessarily reasonably trace NMI's, but
it's something to keep in mind as required support eventually.
Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/