sudo perf record -o pt_ls -kcore -e intel_pt// - ls perf record can make a copy of /proc/kcore if the option -kcore is used, but access to /proc/kcore is restricted e.g. A fairly good kernel image is available in /proc/kcore but to get an accurate image a copy of /proc/kcore needs to be made under the same conditions as the data capture. To also trace kernel space presents a problem, namely kernel self-modifying code. to trace ls userspace-only: perf record -e intel_pt//u lsĪnd profiled with perf report e.g. The simplest thing to do with Intel PT is userspace profiling of small programs. That is because it is easy to capture vastly more data than can possibly be processed. Another limitation is the performance impact of tracing, something that will vary depending on the use-case and architecture. Also symbols need to be provided to make sense of addresses.Ī limitation of Intel PT is that it produces huge amounts of trace data (hundreds of megabytes per second per core) which takes a long time to decode, for example two or three orders of magnitude longer than it took to collect.
#ITRACE MANUAL SOFTWARE#
The software does not have to be recompiled, so Intel PT works with debug or release builds, however the executed images are needed - which makes use in JIT-compiled environments, or with self-modified code, a challenge. Intel PT can be used to understand why and how did software get to a certain point, or behave a certain way. The main distinguishing feature of Intel PT is that the decoder can determine the exact flow of software execution. See below for more information on using those tools. Presently 3 tools support this: perf script, perf report and perf inject. The decoder outputs samples in the same format as samples output by perf hardware events, for example as though the "instructions" or "branches" events had been recorded. For example a TNT packet only tells whether a conditional branch was taken or not taken, so to make use of that packet the decoder must know precisely which instruction was being executed.ĭecoding is done on-the-fly.
#ITRACE MANUAL CODE#
Trace data must be decoded which involves walking the object code and matching the trace data packets. Trace data is collected by perf record and stored within the perf.data file. Intel PT is first supported in Intel Core M and 5th generation Intel Core processors that are based on the Intel micro-architecture code name Broadwell. Technical details are documented in the Intel 64 and IA-32 Architectures Software Developer Manuals, Chapter 36 Intel Processor Trace. Intel Processor Trace (Intel PT) is an extension of Intel Architecture that collects information about software execution such as control flow, execution modes and timings and formats it into highly compressed binary packets. Support for Intel Processor Trace within perf tools Synopsis perf record -e intel_pt// Description
0 kommentar(er)
