realtime:documentation:howto:tools:hwlat
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realtime:documentation:howto:tools:hwlat [2018/08/22 16:54] ebugden Move general information to separate Ftrace page |
realtime:documentation:howto:tools:hwlat [2018/08/24 09:48] (current) ebugden [Ftrace - hwlat tracer] Remove ftrace highlight on kernel doc link |
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| hwlat is an Ftrace tracer designed to detect latencies caused by a system's firmware or hardware. The tracer was originally intended for [[realtime:documentation:howto:debugging:smi-latency:start|detecting SMIs]], but it can detect other low level latencies as well. | hwlat is an Ftrace tracer designed to detect latencies caused by a system's firmware or hardware. The tracer was originally intended for [[realtime:documentation:howto:debugging:smi-latency:start|detecting SMIs]], but it can detect other low level latencies as well. | ||
| - | This article is brief because it is dedicated to a specific Ftrace tracer. More complete information about how to use Ftrace can be found [[realtime:documentation:howto:tools:ftrace|here]]. More details about this tracer can be found in the kernel documentation for Ftrace and in the kernel documentation for the hardware latency detector. | + | This article is brief because it is dedicated to a specific Ftrace tracer. More complete information about how to use Ftrace can be found [[realtime:documentation:howto:tools:ftrace|here]]. More details about this tracer can be found in the kernel documentation for [[https://www.kernel.org/doc/html/latest/trace/ftrace.html#hardware-latency-detector|Ftrace]] and in the kernel documentation for the [[https://www.kernel.org/doc/html/latest/trace/hwlat_detector.html|Hardware Latency Detector]]. |
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| </WRAP> | </WRAP> | ||
| - | Because of a bug, an additional instance of hwlat is started every time 1 is written to tracing_on regardless of whether or not tracing with hwlat is already enabled. When tracing is disabled, only one instance of hwlat will be stopped and the only way to stop the additional instances is to restart the system. Running multiple instances of hwlat can quickly cripple a system so it is best to avoid this. | + | Because of a bug, an additional instance of hwlat is started every time 1 is written to tracing_on regardless of whether or not tracing with hwlat is already enabled. When tracing is disabled, only one instance of hwlat will be stopped and the only way to stop the additional instances is to restart the system. Running multiple instances of hwlat can quickly cripple a system so it is best to avoid this. |
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| + | <WRAP center round todo 60%> | ||
| + | Remove the bug warning when Steven's fix is merged into mainline | ||
| + | </WRAP> | ||
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| ===== Analysis ===== | ===== Analysis ===== | ||
realtime/documentation/howto/tools/hwlat.1534956841.txt.gz · Last modified: 2018/08/22 16:54 by ebugden
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