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diff --git a/doc/dev/perf_histograms.rst b/doc/dev/perf_histograms.rst new file mode 100644 index 000000000..c277ac209 --- /dev/null +++ b/doc/dev/perf_histograms.rst @@ -0,0 +1,677 @@ +================= + Perf histograms +================= + +The perf histograms build on perf counters infrastructure. Histograms are built for a number of counters and simplify gathering data on which groups of counter values occur most often over time. +Perf histograms are currently unsigned 64-bit integer counters, so they're mostly useful for time and sizes. Data dumped by perf histogram can then be feed into other analysis tools/scripts. + +Access +------ + +The perf histogram data are accessed via the admin socket. For example:: + + ceph daemon osd.0 perf histogram schema + ceph daemon osd.0 perf histogram dump + + +Collections +----------- + +The histograms are grouped into named collections, normally representing a subsystem or an instance of a subsystem. For example, the internal ``throttle`` mechanism reports statistics on how it is throttling, and each instance is named something like:: + + + op_r_latency_out_bytes_histogram + op_rw_latency_in_bytes_histogram + op_rw_latency_out_bytes_histogram + ... + + +Schema +------ + +The ``perf histogram schema`` command dumps a json description of which values are available, and what their type is. Each named value as a ``type`` bitfield, with the 5-th bit always set and following bits defined. + ++------+-------------------------------------+ +| bit | meaning | ++======+=====================================+ +| 1 | floating point value | ++------+-------------------------------------+ +| 2 | unsigned 64-bit integer value | ++------+-------------------------------------+ +| 4 | average (sum + count pair) | ++------+-------------------------------------+ +| 8 | counter (vs gauge) | ++------+-------------------------------------+ + +In other words, histogram of type "18" is a histogram of unsigned 64-bit integer values (16 + 2). + +Here is an example of the schema output:: + + { + "AsyncMessenger::Worker-0": {}, + "AsyncMessenger::Worker-1": {}, + "AsyncMessenger::Worker-2": {}, + "mutex-WBThrottle::lock": {}, + "objecter": {}, + "osd": { + "op_r_latency_out_bytes_histogram": { + "type": 18, + "description": "Histogram of operation latency (including queue time) + da ta read", + "nick": "" + }, + "op_w_latency_in_bytes_histogram": { + "type": 18, + "description": "Histogram of operation latency (including queue time) + da ta written", + "nick": "" + }, + "op_rw_latency_in_bytes_histogram": { + "type": 18, + "description": "Histogram of rw operation latency (including queue time) + data written", + "nick": "" + }, + "op_rw_latency_out_bytes_histogram": { + "type": 18, + "description": "Histogram of rw operation latency (including queue time) + data read", + "nick": "" + } + } + } + + +Dump +---- + +The actual dump is similar to the schema, except that there are actual value groups. For example:: + + "osd": { + "op_r_latency_out_bytes_histogram": { + "axes": [ + { + "name": "Latency (usec)", + "min": 0, + "quant_size": 100000, + "buckets": 32, + "scale_type": "log2", + "ranges": [ + { + "max": -1 + }, + { + "min": 0, + "max": 99999 + }, + { + "min": 100000, + "max": 199999 + }, + { + "min": 200000, + "max": 399999 + }, + { + "min": 400000, + "max": 799999 + }, + { + "min": 800000, + "max": 1599999 + }, + { + "min": 1600000, + "max": 3199999 + }, + { + "min": 3200000, + "max": 6399999 + }, + { + "min": 6400000, + "max": 12799999 + }, + { + "min": 12800000, + "max": 25599999 + }, + { + "min": 25600000, + "max": 51199999 + }, + { + "min": 51200000, + "max": 102399999 + }, + { + "min": 102400000, + "max": 204799999 + }, + { + "min": 204800000, + "max": 409599999 + }, + { + "min": 409600000, + "max": 819199999 + }, + { + "min": 819200000, + "max": 1638399999 + }, + { + "min": 1638400000, + "max": 3276799999 + }, + { + "min": 3276800000, + "max": 6553599999 + }, + { + "min": 6553600000, + "max": 13107199999 + }, + { + "min": 13107200000, + "max": 26214399999 + }, + { + "min": 26214400000, + "max": 52428799999 + }, + { + "min": 52428800000, + "max": 104857599999 + }, + { + "min": 104857600000, + "max": 209715199999 + }, + { + "min": 209715200000, + "max": 419430399999 + }, + { + "min": 419430400000, + "max": 838860799999 + }, + { + "min": 838860800000, + "max": 1677721599999 + }, + { + "min": 1677721600000, + "max": 3355443199999 + }, + { + "min": 3355443200000, + "max": 6710886399999 + }, + { + "min": 6710886400000, + "max": 13421772799999 + }, + { + "min": 13421772800000, + "max": 26843545599999 + }, + { + "min": 26843545600000, + "max": 53687091199999 + }, + }, + { + "min": 53687091200000 + } + ] + }, + { + "name": "Request size (bytes)", + "min": 0, + "quant_size": 512, + "buckets": 32, + "scale_type": "log2", + "ranges": [ + { + "max": -1 + }, + { + "min": 0, + "max": 511 + }, + { + "min": 512, + "max": 1023 + }, + { + "min": 1024, + "max": 2047 + }, + { + "min": 2048, + "max": 4095 + }, + { + "min": 4096, + "max": 8191 + }, + { + "min": 8192, + "max": 16383 + }, + { + "min": 16384, + "max": 32767 + }, + { + "min": 32768, + "max": 65535 + }, + { + "min": 65536, + "max": 131071 + }, + { + "min": 131072, + "max": 262143 + }, + { + "min": 262144, + "max": 524287 + }, + { + "min": 524288, + "max": 1048575 + }, + { + "min": 1048576, + "max": 2097151 + }, + { + "min": 2097152, + "max": 4194303 + }, + { + "min": 4194304, + "max": 8388607 + }, + { + "min": 8388608, + "max": 16777215 + }, + { + "min": 16777216, + "max": 33554431 + }, + { + "min": 33554432, + "max": 67108863 + }, + { + "min": 67108864, + "max": 134217727 + }, + { + "min": 134217728, + "max": 268435455 + }, + { + "min": 268435456, + "max": 536870911 + }, + { + "min": 536870912, + "max": 1073741823 + }, + { + "min": 1073741824, + "max": 2147483647 + }, + { + "min": 2147483648, + "max": 4294967295 + }, + { + "min": 4294967296, + "max": 8589934591 + }, + { + "min": 8589934592, + "max": 17179869183 + }, + { + "min": 17179869184, + "max": 34359738367 + }, + { + "min": 34359738368, + "max": 68719476735 + }, + { + "min": 68719476736, + "max": 137438953471 + }, + { + "min": 137438953472, + "max": 274877906943 + }, + { + "min": 274877906944 + } + ] + } + ], + "values": [ + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ], + [ + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0, + 0 + ] + ] + } + }, + +This represents the 2d histogram, consisting of 9 history entrires and 32 value groups per each history entry. +"Ranges" element denote value bounds for each of value groups. "Buckets" denote amount of value groups ("buckets"), +"Min" is a minimum accepted valaue, "quant_size" is quantization unit and "scale_type" is either "log2" (logarhitmic +scale) or "linear" (linear scale). +You can use histogram_dump.py tool (see src/tools/histogram_dump.py) for quick visualisation of existing histogram +data. |