Fix time going backwards on biolatency and biotop #2660
Commits on Dec 22, 2019
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Fix time going backwards on biolatency.py
When, for some reason, the bpf_ktime_get_ns() in trace_req_done results in a number smaller than the one stored in trace_req_start, the latency for this request goes all wrong and the histogram shows something like this: Tracing block device I/O... Hit Ctrl-C to end. ^C usecs : count distribution 0 -> 1 : 0 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 25 | | 32 -> 63 : 32 | | 64 -> 127 : 254 | | 128 -> 255 : 2164 |* | 256 -> 511 : 5421 |*** | 512 -> 1023 : 29795 |********************| 1024 -> 2047 : 17042 |*********** | 2048 -> 4095 : 6400 |**** | 4096 -> 8191 : 4935 |*** | 8192 -> 16383 : 588 | | 16384 -> 32767 : 54 | | 32768 -> 65535 : 14 | | 65536 -> 131071 : 4 | | 131072 -> 262143 : 4 | | 262144 -> 524287 : 0 | | 524288 -> 1048575 : 0 | | 1048576 -> 2097151 : 0 | | 2097152 -> 4194303 : 0 | | 4194304 -> 8388607 : 0 | | 8388608 -> 16777215 : 0 | | 16777216 -> 33554431 : 0 | | 33554432 -> 67108863 : 0 | | 67108864 -> 134217727 : 0 | | 134217728 -> 268435455 : 0 | | 268435456 -> 536870911 : 0 | | 536870912 -> 1073741823 : 0 | | 1073741824 -> 2147483647 : 0 | | 2147483648 -> 4294967295 : 0 | | 4294967296 -> 8589934591 : 0 | | 8589934592 -> 17179869183 : 0 | | 17179869184 -> 34359738367 : 0 | | 34359738368 -> 68719476735 : 0 | | 68719476736 -> 137438953471 : 0 | | 137438953472 -> 274877906943 : 0 | | 274877906944 -> 549755813887 : 0 | | 549755813888 -> 1099511627775 : 0 | | 1099511627776 -> 2199023255551 : 0 | | 2199023255552 -> 4398046511103 : 0 | | 4398046511104 -> 8796093022207 : 0 | | 8796093022208 -> 17592186044415 : 0 | | 17592186044416 -> 35184372088831 : 0 | | 35184372088832 -> 70368744177663 : 0 | | 70368744177664 -> 140737488355327 : 0 | | 140737488355328 -> 281474976710655 : 0 | | 281474976710656 -> 562949953421311 : 0 | | 562949953421312 -> 1125899906842623 : 0 | | 1125899906842624 -> 2251799813685247 : 0 | | 2251799813685248 -> 4503599627370495 : 0 | | 4503599627370496 -> 9007199254740991 : 0 | | 9007199254740992 -> 18014398509481983 : 0 | | 18014398509481984 -> 36028797018963967 : 17 | | With this bug corrected, the output is: Tracing block device I/O... Hit Ctrl-C to end. ^C usecs : count distribution 0 -> 1 : 0 | | 2 -> 3 : 0 | | 4 -> 7 : 0 | | 8 -> 15 : 0 | | 16 -> 31 : 163 | | 32 -> 63 : 339 | | 64 -> 127 : 258 | | 128 -> 255 : 2259 |** | 256 -> 511 : 5677 |****** | 512 -> 1023 : 32662 |****************************************| 1024 -> 2047 : 20252 |************************ | 2048 -> 4095 : 12544 |*************** | 4096 -> 8191 : 11006 |************* | 8192 -> 16383 : 1230 |* | 16384 -> 32767 : 201 | | 32768 -> 65535 : 544 | | 65536 -> 131071 : 746 | | 131072 -> 262143 : 881 |* | 262144 -> 524287 : 309 | | Which is very easier to read. -
Fix time going backwards on biolatency.py
When, for some reason, the bpf_ktime_get_ns() in trace_req_completion results in a number smaller than the one stored in trace_req_start, the latency for this request goes all wrong and results in a very huge number appears in the biotop output. Added a check to discard the measured request when this situation happens.
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Last commit changes delta_us to delta, but the operation to convert was wrong (was * 1000, but needs to be / 1000)
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Added dropped events due to backwards time counter
Added a message warning the user about the amount of IO requests that are dropped due to bpf_ktime_get_ns() at the end of request being older than the one collected at start.
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Added dropped events due to backwards time counter
Added a message warning the user about the amount of IO requests that are dropped due to bpf_ktime_get_ns() at the end of request being older than the one collected at start.
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