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Diffstat (limited to 'tools/perf/Documentation/perf-intel-pt.txt')
| -rw-r--r-- | tools/perf/Documentation/perf-intel-pt.txt | 63 |
1 files changed, 61 insertions, 2 deletions
diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt index f4cd49a7fcdb..d5a266d7f15b 100644 --- a/tools/perf/Documentation/perf-intel-pt.txt +++ b/tools/perf/Documentation/perf-intel-pt.txt @@ -825,6 +825,7 @@ The letters are: l synthesize last branch entries (use with i or x) L synthesize last branch entries on existing event records s skip initial number of events + q quicker (less detailed) decoding "Instructions" events look like they were recorded by "perf record -e instructions". @@ -871,11 +872,24 @@ Developer Manuals. Error events show where the decoder lost the trace. Error events are quite important. Users must know if what they are seeing is a complete -picture or not. +picture or not. The "e" option may be followed by flags which affect what errors +will or will not be reported. Each flag must be preceded by either '+' or '-'. +The flags supported by Intel PT are: + -o Suppress overflow errors + -l Suppress trace data lost errors +For example, for errors but not overflow or data lost errors: + + --itrace=e-o-l The "d" option will cause the creation of a file "intel_pt.log" containing all decoded packets and instructions. Note that this option slows down the decoder -and that the resulting file may be very large. +and that the resulting file may be very large. The "d" option may be followed +by flags which affect what debug messages will or will not be logged. Each flag +must be preceded by either '+' or '-'. The flags support by Intel PT are: + -a Suppress logging of perf events + +a Log all perf events +By default, logged perf events are filtered by any specified time ranges, but +flag +a overrides that. In addition, the period of the "instructions" event can be specified. e.g. @@ -956,6 +970,51 @@ at the beginning. This is useful to ignore initialization code. skips the first million instructions. +The q option changes the way the trace is decoded. The decoding is much faster +but much less detailed. Specifically, with the q option, the decoder does not +decode TNT packets, and does not walk object code, but gets the ip from FUP and +TIP packets. The q option can be used with the b and i options but the period +is not used. The q option decodes more quickly, but is useful only if the +control flow of interest is represented or indicated by FUP, TIP, TIP.PGE, or +TIP.PGD packets (refer below). However the q option could be used to find time +ranges that could then be decoded fully using the --time option. + +What will *not* be decoded with the (single) q option: + + - direct calls and jmps + - conditional branches + - non-branch instructions + +What *will* be decoded with the (single) q option: + + - asynchronous branches such as interrupts + - indirect branches + - function return target address *if* the noretcomp config term (refer + config terms section) was used + - start of (control-flow) tracing + - end of (control-flow) tracing, if it is not out of context + - power events, ptwrite, transaction start and abort + - instruction pointer associated with PSB packets + +Note the q option does not specify what events will be synthesized e.g. the p +option must be used also to show power events. + +Repeating the q option (double-q i.e. qq) results in even faster decoding and even +less detail. The decoder decodes only extended PSB (PSB+) packets, getting the +instruction pointer if there is a FUP packet within PSB+ (i.e. between PSB and +PSBEND). Note PSB packets occur regularly in the trace based on the psb_period +config term (refer config terms section). There will be a FUP packet if the +PSB+ occurs while control flow is being traced. + +What will *not* be decoded with the qq option: + + - everything except instruction pointer associated with PSB packets + +What *will* be decoded with the qq option: + + - instruction pointer associated with PSB packets + + dump option ~~~~~~~~~~~ |