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perf intel-pt: Add documentation for Event Trace and TNT disable
Add documentation for Event Trace and TNT disable to the perf Intel PT man page. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Link: https://lore.kernel.org/r/20220124084201.2699795-26-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Adrian Hunter
Arnaldo Carvalho de Melo
parent
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24e3599c5a
1 changed files with 102 additions and 2 deletions
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@ -108,9 +108,10 @@ displayed as follows:
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perf script --itrace=ibxwpe -F+flags
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The flags are "bcrosyiABExgh" which stand for branch, call, return, conditional,
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The flags are "bcrosyiABExghDt" which stand for branch, call, return, conditional,
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system, asynchronous, interrupt, transaction abort, trace begin, trace end,
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in transaction, VM-entry, and VM-exit respectively.
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in transaction, VM-entry, VM-exit, interrupt disabled, and interrupt disable
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toggle respectively.
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perf script also supports higher level ways to dump instruction traces:
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@ -483,6 +484,30 @@ pwr_evt Enable power events. The power events provide information about
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which contains "1" if the feature is supported and
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"0" otherwise.
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event Enable Event Trace. The events provide information about asynchronous
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events.
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Support for this feature is indicated by:
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/sys/bus/event_source/devices/intel_pt/caps/event_trace
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which contains "1" if the feature is supported and
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"0" otherwise.
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notnt Disable TNT packets. Without TNT packets, it is not possible to walk
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executable code to reconstruct control flow, however FUP, TIP, TIP.PGE
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and TIP.PGD packets still indicate asynchronous control flow, and (if
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return compression is disabled - see noretcomp) return statements.
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The advantage of eliminating TNT packets is reducing the size of the
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trace and corresponding tracing overhead.
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Support for this feature is indicated by:
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/sys/bus/event_source/devices/intel_pt/caps/tnt_disable
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which contains "1" if the feature is supported and
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"0" otherwise.
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AUX area sampling option
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~~~~~~~~~~~~~~~~~~~~~~~~
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@ -876,6 +901,8 @@ The letters are:
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p synthesize "power" events (incl. PSB events)
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c synthesize branches events (calls only)
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r synthesize branches events (returns only)
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o synthesize PEBS-via-PT events
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I synthesize Event Trace events
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e synthesize tracing error events
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d create a debug log
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g synthesize a call chain (use with i or x)
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@ -1371,6 +1398,79 @@ There were none.
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:17006 17006 [001] 11500.262869216: ffffffff8220116e error_entry+0xe ([guest.kernel.kallsyms]) pushq %rax
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Event Trace
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-----------
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Event Trace records information about asynchronous events, for example interrupts,
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faults, VM exits and entries. The information is recorded in CFE and EVD packets,
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and also the Interrupt Flag is recorded on the MODE.Exec packet. The CFE packet
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contains a type field to identify one of the following:
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1 INTR interrupt, fault, exception, NMI
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2 IRET interrupt return
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3 SMI system management interrupt
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4 RSM resume from system management mode
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5 SIPI startup interprocessor interrupt
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6 INIT INIT signal
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7 VMENTRY VM-Entry
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8 VMEXIT VM-Entry
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9 VMEXIT_INTR VM-Exit due to interrupt
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10 SHUTDOWN Shutdown
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For more details, refer to the Intel 64 and IA-32 Architectures Software
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Developer Manuals (version 076 or later).
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The capability to do Event Trace is indicated by the
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/sys/bus/event_source/devices/intel_pt/caps/event_trace file.
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Event trace is selected for recording using the "event" config term. e.g.
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perf record -e intel_pt/event/u uname
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Event trace events are output using the --itrace I option. e.g.
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perf script --itrace=Ie
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perf script displays events containing CFE type, vector and event data,
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in the form:
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evt: hw int (t) cfe: INTR IP: 1 vector: 3 PFA: 0x8877665544332211
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The IP flag indicates if the event binds to an IP, which includes any case where
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flow control packet generation is enabled, as well as when CFE packet IP bit is
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set.
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perf script displays events containing changes to the Interrupt Flag in the form:
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iflag: t IFLAG: 1->0 via branch
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where "via branch" indicates a branch (interrupt or return from interrupt) and
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"non branch" indicates an instruction such as CFI, STI or POPF).
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In addition, the current state of the interrupt flag is indicated by the presence
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or absence of the "D" (interrupt disabled) perf script flag. If the interrupt
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flag is changed, then the "t" flag is also included i.e.
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no flag, interrupts enabled IF=1
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t interrupts become disabled IF=1 -> IF=0
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D interrupts are disabled IF=0
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Dt interrupts become enabled IF=0 -> IF=1
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The intel-pt-events.py script illustrates how to access Event Trace information
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using a Python script.
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TNT Disable
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-----------
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TNT packets are disabled using the "notnt" config term. e.g.
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perf record -e intel_pt/notnt/u uname
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In that case the --itrace q option is forced because walking executable code
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to reconstruct the control flow is not possible.
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SEE ALSO
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--------
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