Em Thu, Jan 22, 2009 at 09:36:53AM +1100, Greg Banks escreveu: > Chuck Lever wrote: > > > > > > I think we need to visit this issue on a case-by-case basis. > > Sometimes dprintk is appropriate. Sometimes printk(KERN_ERR). > > Sometimes a performance metric. > Well said. > > > Trond has always maintained that dprintk() is best for developers, but > > probably inappropriate for field debugging, > It's not a perfect tool but it beats nothing at all. > > and I think that may also > > apply to trace points. > It depends on whether distros can be convinced to enable it by default, > and install by default any necessary userspace infrastructure. The > most important thing for field debugging is Just Knowing that you have > all the bits necessary to perform useful debugging without having to > find some RPM that matches the kernel that the machine is actually > running now, and not the one that was present when the machine was > installed. Exactly, that is why an ftrace plugin, that only when selected using echo "nfs" > /debug/tracing/current_tracer will activate the tracepoints and provide output via /debug/tracing/trace or /deb/tracing/trace_pipe, possibly combined with other ftrace plugins such as the stacktrace, blktrace, etc. I.e. no need at all for any matching userspace tool, near zero impact when not activated, useful, if done right, for both developers and for admins. Again, an example can be found in the blktrace ftrace plugin[1], that instead of adding a requirement will eventually drop an existing, well established one (blktrace(8)). - Arnaldo [1] http://lkml.org/lkml/2009/1/20/190 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
