On Wed, 2012-11-14 at 17:26 +0900, Yoshihiro YUNOMAE wrote: > Thank you for commenting on my patch set. > > (2012/11/14 11:31), Steven Rostedt wrote: > > On Tue, 2012-11-13 at 18:03 -0800, David Sharp wrote: > >> On Tue, Nov 13, 2012 at 6:00 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > >>> On Wed, 2012-11-14 at 10:36 +0900, Yoshihiro YUNOMAE wrote: > >>> > >>>> To merge the data like previous pattern, we apply this patch set. Then, we can > >>>> get TSC offset of the guest as follows: > >>>> > >>>> $ dmesg | grep kvm > >>>> [ 57.717180] kvm: (2687) write TSC offset 18446743360465545001, now clock ## > >>>> ^^^^ ^^^^^^^^^^^^^^^^^^^^ | > >>>> PID TSC offset | > >>>> HOST TSC value --+ > >>>> > >>> > >>> Using printk to export something like this is IMO a nasty hack. > >>> > >>> Can't we create a /sys or /proc file to export the same thing? > >> > >> Since the value changes over the course of the trace, and seems to be > >> part of the context of the trace, I think I'd include it as a > >> tracepoint. > >> > > > > I'm fine with that too. > > Using some tracepoint is a nice idea, but there is one problem. Here, > our discussion point is "the event which TSC offset is changed does not > frequently occur, but the buffer must keep the event data." If you can hold off a bit, for the 3.9 window, I plan on pushing multiple buffers for ftrace. That is, you can create a separate buffer just for the TSC offset events: cd /sys/kernel/debug echo tsc > instances/new echo 1 > instances/tsc/events/tsc/offset/enable Then the buffer will be used only for that event. The code is pretty much ready, but I want to test it more before the 3.8 window opens, which is why I'm waiting for 3.9. You can see the latest version here: git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git branch: rfc/multi-buffers-v7 -- Steve -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
