Messages in this thread | | | Date | Thu, 23 Apr 2015 21:51:47 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC][PATCH 0/4] tracing: Add new hwlat_detector tracer |
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On Thu, 23 Apr 2015, Steven Rostedt wrote: > This is the port of the hardware latency detector from the -rt patch > to mainline. Instead of keeping it as a device that had its own debugfs > filesystem infrastructure, it made more sense to make it into a tracer > like irqsoff and wakeup latency tracers currently are. > > With this patch set, a new tracer is enabled if CONFIG_HWLAT_TRACER is > enabled. Inside the available_tracers file will be hwlat_detector. > > # cd /sys/kernel/debug/tracing > # echo hwlat_detector > current_tracer > > will enable the hwlat_detector that will create per cpu kernel threads > (which cpus is defined by the tracing/hwlat_detector/cpumask, default > is just CPU 0). > > Like the other tracers (function, function_graph, preemptirqsoff, > and mmiotracer), the hwlat_detector can add a significant performance > penalty when enabled. As each of the threads created will go into a spin > checking the trace_local_clock (sched_clock) for any gaps of time > and will report them if they are greater than the threshold defined > by tracing/tracing_thresh (usecs, default 10). The spin is performed with > interrupts disabled and runs for "width" usecs in "window" usecs time. The
That's fine, but this still lacks a detection of NMI disturbance. We've seen false positives reported over and over when stuff like the NMI watchdog or perf was enabled while running this.
Aside of that isn't there a way to detect SMI crap with performance counters on recent hardware?
Thanks,
tglx
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