On Thu, Oct 14, 2010 at 01:43:52PM +0200, Avi Kivity wrote: > On 10/14/2010 01:41 PM, Gleb Natapov wrote: > >> >> >So what do you propose? I see no issue with my original patch. > >> >> > >> >> Record both errno and exit_reason. While they're never both valid > >> >> at the same time, they're both necessary. > >> >> > >> >If they can't be valid at the same time, why not record one of them? > >> > >> If you record just one, you don't know if the other one happened. > >> > >I mean to record type/value. So it can be (type error/value -EINVAL) or > >(type exit/value HALT). The goal is to not print non-relevant info in > >ftrace, but we can do the same with recording errno and exit_reason and > >show only exit_reason is errno>=0 or errno otherwise. > > That's fine. As long as you don't drop information. > > >> >The > >> >one that happened? Also any error other then -EINTR will cause qemu to > >> >stop, so it is not very interesting. And ioctl return value can be > >> >traced by strace anyway. > >> > >> You can't correlate it with ftrace. > >> > >True. But given that the only interesting error code in -EINTR I do not > >know if this is useful, but potentially may generate a lot of events in > >ftrace. Sometimes too much info is almost as bad as not enough and if we > >will use the same event for both exit_reason and errno it will be > >impossible to enable one without the other. > > You can always filter excess information away. If you're looking > for exits to userspace (a major performance issue) then you want to > see both normal exits and signal exits. > How do I do it via /debug file system? Now I just echo name of the event I am interested in set_event, how do I add filter to that? -- Gleb. -- 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
