Em Sat, 23 Nov 2013 17:54:48 +0100 Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > On 11/23/2013 05:30 PM, Sylwester Nawrocki wrote: > > Hi, > > > > On 11/23/2013 12:25 PM, Hans Verkuil wrote: > >> Hi Wade, > >> > >> On 11/22/2013 08:48 PM, Wade Farnsworth wrote: > >>> Add tracepoints to the QBUF and DQBUF ioctls to enable rudimentary > >>> performance measurements using standard kernel tracers. > >>> > >>> Signed-off-by: Wade Farnsworth<wade_farnsworth@xxxxxxxxxx> > >>> --- > >>> > >>> This is the update to the RFC patch I posted a few weeks back. I've added > >>> several bits of metadata to the tracepoint output per Mauro's suggestion. > >> > >> I don't like this. All v4l2 ioctls can already be traced by doing e.g. > >> echo 1 (or echo 2)>/sys/class/video4linux/video0/debug. > >> > >> So this code basically duplicates that functionality. It would be nice to be able > >> to tie in the existing tracing code (v4l2-ioctl.c) into tracepoints. > > > > I think it would be really nice to have this kind of support for standard > > traces at the v4l2 subsystem. Presumably it could even gradually replace > > the v4l2 custom debug infrastructure. > > > > If I understand things correctly, the current tracing/profiling > > infrastructure > > is much less invasive than inserting printks all over, which may cause > > changes > > in control flow. I doubt the system could be reliably profiled by > > enabling all > > those debug prints. > > > > So my vote would be to add support for standard tracers, like in other > > subsystems in the kernel. > > The reason for the current system is to trace which ioctls are called in > what order by a misbehaving application. It's very useful for that, > especially when trying to debug user problems. > > I don't mind switching to tracepoints as long as this functionality is > kept one way or another. I agree with Sylwester: we should move to tracepoints, and this is a good start. Regards, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
