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Subject[PATCH v8 0/4] perf: add support for profiling jitted code
This patch series extends perf record/report/annotate to enable
profiling of jitted (just-in-time compiled) code. The current
perf tool provides very limited support for profiling jitted
code for some runtime environments. But the support is experimental
and cannot be used in complex environments. It relies on files
in /tmp, for instance. It does not support annotate mode or
rejitted code.

This patch series adds a better way of profiling jitted code
with the following advantages:
- support any jitted code environment (some with modifications)
- support Java runtime with JVMTI interface with no modifications
- provides a portable JVMTI agent library
- known to support V8 runtime
- known to support DART runtime
- supports code rejitting and code movements
- no files in /tmp
- meta-data file is unique to each run
- no changes to perf report/annotate
- support per-thread and system-wide profiling
- support monitoring of multiple simultaneous Jit runtimes
- source level view in perf annotate
- works on x86_64, i386, arm32, arm64

The support is based on cooperation with the runtime. For Java runtimes,
supporting the JVMTI interface, there is no change necessary. For other
runtimes, modifications are necessary to emit the meta-data to support
symbolization, annotation, source lines correlation of the samples.
Those modifications are relatively straighforward, some have been
implemented in V8 and DART.

The jit environment emits a binary dump file which contains the jitted
code (in raw format) and meta-data describing the mapping of functions.
The binary format is documented in the jitdump.h header file. It is
adapted from the OProfile jitdump format.

To enable synchronization of the runtime MMAPs with those recorded by
the kernel on behalf of the perf tool, the runtime needs to timestamp
any record in the dump file using the same time source. This is possible
since Linux 4.1 where the kernel supports per event timestamp clock source.
In the case of the JVMTI agent, the clock used is CLOCK_MONOTONIC, thus
perf record is invoked with -k mono such that it matches the agent.

The current support only works when the runtime is monitored from
start to finish: perf record java my_class.

Once the run is completed, the jitdump file needs to be injected into
the file. This is accomplished by using the perf inject command.
This will also generate an ELF image for each jitted function. The
injected MMAP records will point to these ELF images. The reasoning
behind using ELF images is that it makes processing for perf report
and annotate automatic and transparent. It also makes it easier to
package and analyze on a remote machine. Binutils tools can decode
the ELF images easily.

The reporting is unchanged, simply invoke perf report or perf annotate
on the modified file. The jitted code will appear symbolized
and the assembly view will display the instruction level profile and
source level profile.

As an added bonus, the series includes support for demangling function
signature from OpenJDK.

Furthermore, we believe there is a way to skip the perf inject phase
and have perf report/annotate directly inject the MMAP records
on the fly during processing of the file. Perf report would
also generate the ELF files if necessary. Such optimization, would
make using this extension seamless in system-wide mode and larger
environments. This will be added in a later update as well.

In V2, we have switched to Pawell Moll and David Ahern posix
clock kernel module instead. We have dropped the patch which
modified the arguments to map_init() because the change was
not used. We are not printing the return type of Java methods
anymore and have made the Java demangler a separate module.
We also rebased to 3.19.0+ from tip.git.

In V3, we switched to Pawel Moll's CLOCK_MONOTONIC perf
clock patches. This patch switch perf_events from sched_clock
to CLOCK_MONOTONIC, a clock source which is available to users.

In V4, we rebased to 4.0-rc5. We also simplified the process by
getting rid of the requirement to pass the jitdump file name to
perf inject. Now, perf injects automtically detects if jitdumps
were generated and it merges the relevant meta-data. This is
accomplished by having the jit runtime mmap the jitdump file
for the purpose of creating a MMAP record in the file.
That MMAP contains all the info to locate the jitdump file and
generate the ELF images for jitted functions.

In V5, we rebase to acme's perf/core branch (instead of tip.git).
We fixed some bswap issues, switched to using scnprintf() and fixed
formatting issues. Also made sure all the files were included in the
patches. We also fix one error message in the JVMTI agent.

In V6, we switched back to using tip.git to leverage PeterZ's clockid
patch for perf_events in 4.0.0-rc6. Clock source can now be specified
per event and they are connected with the MONOTONIC Posix clock. We
leverage this extension to timestamp samples in the jit runtime and
correlate them with perf samples. Notice the -k mono option in perf
record example below.

In V7, we rebased to 4.3.0-rc3 using tip.git (at commit 0dc7757).
We fixed several issues in the agent. We also added source line
information in the jitdump file from the JVMTI agent. This is
still experimental and probably has some issues. The source
line info is encoded in DWARF2 format in each ELF image. The
code to do this is leveraged from Oprofile with some fixes
and cleanups.

In V8, we rebased to 4.4.0-rc2 using tip.git (at commit 9962da9).
We received great contributions from Andrian Hunter (
He has fixed several issues in the jitdump injection code, see changelog
of the patch. The jitdump header has a new flags field to be used for
Intel PT. The series has been verified to work on x86_64, i386, arm32
and arm64 running 4.1 or later.

To use the new feature:
- need to run with 4.1 or later
- compile perf
- cd tools/perf/jvmti; make; install wherever is appropriate

Example using openJDK:
$ perf record -k mono java my_class
$ perf inject -i -jit -o
$ perf report -i

Thanks to all the contributors and testers. Special thanks
to PeterZ for adding the clock source to perf_events and solving
the problem of common timesource for user and kernel level samples.
Thanks to the Oprofile authors for the DWARF2 source line code

Special thanks to Adrian Hunter for his many bug fixes and improvements
for the V8 version of this series.


Stephane Eranian (4):
perf tools: add Java demangling support
perf inject: add jitdump mmap injection support
perf tools: add JVMTI agent library
perf/jit: add source line info support

tools/build/Makefile.feature | 2 +
tools/build/feature/Makefile | 4 +
tools/build/feature/test-all.c | 5 +
tools/build/feature/test-libcrypto.c | 17 +
tools/perf/Documentation/perf-inject.txt | 7 +
tools/perf/builtin-inject.c | 93 +++++
tools/perf/config/Makefile | 11 +
tools/perf/jvmti/Makefile | 73 ++++
tools/perf/jvmti/jvmti_agent.c | 465 +++++++++++++++++++++
tools/perf/jvmti/jvmti_agent.h | 36 ++
tools/perf/jvmti/libjvmti.c | 304 ++++++++++++++
tools/perf/util/Build | 7 +
tools/perf/util/demangle-java.c | 199 +++++++++
tools/perf/util/demangle-java.h | 10 +
tools/perf/util/genelf.c | 449 +++++++++++++++++++++
tools/perf/util/genelf.h | 67 +++
tools/perf/util/genelf_debug.c | 610 ++++++++++++++++++++++++++++
tools/perf/util/jit.h | 15 +
tools/perf/util/jitdump.c | 672 +++++++++++++++++++++++++++++++
tools/perf/util/jitdump.h | 124 ++++++
tools/perf/util/symbol-elf.c | 3 +
21 files changed, 3173 insertions(+)
create mode 100644 tools/build/feature/test-libcrypto.c
create mode 100644 tools/perf/jvmti/Makefile
create mode 100644 tools/perf/jvmti/jvmti_agent.c
create mode 100644 tools/perf/jvmti/jvmti_agent.h
create mode 100644 tools/perf/jvmti/libjvmti.c
create mode 100644 tools/perf/util/demangle-java.c
create mode 100644 tools/perf/util/demangle-java.h
create mode 100644 tools/perf/util/genelf.c
create mode 100644 tools/perf/util/genelf.h
create mode 100644 tools/perf/util/genelf_debug.c
create mode 100644 tools/perf/util/jit.h
create mode 100644 tools/perf/util/jitdump.c
create mode 100644 tools/perf/util/jitdump.h


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