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Diffstat (limited to 'tools/perf/Documentation/intel-pt.txt')
| -rw-r--r-- | tools/perf/Documentation/intel-pt.txt | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/tools/perf/Documentation/intel-pt.txt b/tools/perf/Documentation/intel-pt.txt index 60d99e5e7921..50c5b60101bd 100644 --- a/tools/perf/Documentation/intel-pt.txt +++ b/tools/perf/Documentation/intel-pt.txt @@ -103,6 +103,36 @@ The flags are "bcrosyiABEx" which stand for branch, call, return, conditional, system, asynchronous, interrupt, transaction abort, trace begin, trace end, and in transaction, respectively. +Another interesting field that is not printed by default is 'ipc' which can be +displayed as follows: + + perf script --itrace=be -F+ipc + +There are two ways that instructions-per-cycle (IPC) can be calculated depending +on the recording. + +If the 'cyc' config term (see config terms section below) was used, then IPC is +calculated using the cycle count from CYC packets, otherwise MTC packets are +used - refer to the 'mtc' config term. When MTC is used, however, the values +are less accurate because the timing is less accurate. + +Because Intel PT does not update the cycle count on every branch or instruction, +the values will often be zero. When there are values, they will be the number +of instructions and number of cycles since the last update, and thus represent +the average IPC since the last IPC for that event type. Note IPC for "branches" +events is calculated separately from IPC for "instructions" events. + +Also note that the IPC instruction count may or may not include the current +instruction. If the cycle count is associated with an asynchronous branch +(e.g. page fault or interrupt), then the instruction count does not include the +current instruction, otherwise it does. That is consistent with whether or not +that instruction has retired when the cycle count is updated. + +Another note, in the case of "branches" events, non-taken branches are not +presently sampled, so IPC values for them do not appear e.g. a CYC packet with a +TNT packet that starts with a non-taken branch. To see every possible IPC +value, "instructions" events can be used e.g. --itrace=i0ns + While it is possible to create scripts to analyze the data, an alternative approach is available to export the data to a sqlite or postgresql database. Refer to script export-to-sqlite.py or export-to-postgresql.py for more details, |