On Tue, Apr 24, 2018 at 8:56 AM, Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > On Mon, Apr 23, 2018 at 05:22:44PM -0400, Steven Rostedt wrote: >> On Mon, 23 Apr 2018 13:12:21 -0400 (EDT) >> Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: >> >> >> > I'm inclined to explicitly declare the tracepoints with their given >> > synchronization method. Tracepoint probe callback functions for currently >> > existing tracepoints expect to have preemption disabled when invoked. >> > This assumption will not be true anymore for srcu-tracepoints. >> >> Actually, why not have a flag attached to the tracepoint_func that >> states if it expects preemption to be enabled or not? If a >> trace_##event##_srcu() is called, then simply disable preemption before >> calling the callbacks for it. That way if a callback is fine for use >> with srcu, then it would require calling >> >> register_trace_##event##_may_sleep(); >> >> Then if someone uses this on a tracepoint where preemption is disabled, >> we simply do not call it. > > One more stupid question... If we are having to trace so much stuff > in the idle loop, are we perhaps grossly overstating the extent of that > "idle" loop? For being called "idle", this code seems quite busy! ;-) The performance hit I am observing is when running a heavy workload, like hackbench or something like that. That's what I am trying to correct. By the way is there any limitation on using SRCU too early during boot? I backported Mathieu's srcu tracepoint patches but the kernel hangs pretty early in the boot. I register lockdep probes in start_kernel. I am hoping that's not why. I could also have just screwed up the backporting... may be for my testing, I will just replace the rcu API with the srcu instead of all of Mathieu's new TRACE_EVENT macros for SRCU, since all I am trying to do right now is measure the performance of my patches with SRCU. thanks, - Joel -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
