D-FOT User Guide

Overview

Dynamic Feedback-directed Optimization Tool (D-FOT) aims to enable automatic and seamless feedback-directed optimizations for applications, improving both usability and performance. The framework is planned to support two types of dynamic optimizations: startup time optimization and runtime optimization. Currently, startup time optimization has been implemented based on the oeAware online tuning framework. Startup time optimization: During application running, sampling and feedback-directed optimization are automatically performed. Once optimization is complete, the optimized version is automatically used in the next startup without requiring any user intervention. After a restart, the application is automatically launched with the optimized version. Runtime optimization: During application running, sampling and feedback-directed optimization are automatically performed. No user intervention is required. The optimized version can be enabled after minimal interruptions.

Software Architecture Description

The framework consists of the following modules:

Sampling data processing based on libkperf
sysboost-based startup handover and binary optimization
Binary feedback optimization based on llvm-bolt
Implementation of the oeAware tuning plugin dfot_tuner_sysboost

Dependency Items

OS requirements: Currently, openEuler 22.03 LTS SP4 and openEuler 25.03 are supported. The following dependent components can be installed using yum.

Component	Code Repository	Description
oeAware-manager	https://gitee.com/openeuler/oeAware-manager	Online transparent service tuning framework
libkperf	https://gitee.com/openeuler/libkperf	Lightweight in-memory collection tool
sysboost	https://gitee.com/openeuler/sysboost	Microarchitecture tuning tool
llvm-bolt	https://gitee.com/src-openeuler/llvm-bolt	Binary optimizer

Procedure

Prerequisites for Applications to Be Optimized

The binary to be optimized must contain relocation information. For self-compiled software, the -Wl,-q linker option must be added during compilation. For example, for MySQL, add cmake .. -DCMAKE_INSTALL_PREFIX=/usr/local/mysql -DBUILD_CONFIG=mysql_release -DWITH_BOOST=../boost -DCMAKE_C_LINK_FLAGS="-Wl,-q" -DCMAKE_CXX_LINK_FLAGS="-Wl,-q". For openEuler software packages, the relocation package of the corresponding application will be provided and can be directly installed.
Check whether the target binary contains relocation information: When the -Wl,-q linker option is effective, the binary will include RELA sections. You can check this using readelf -SW /path/to/bin. For example, in MySQL, before adding the option, only the .rela.dyn and .rela.plt sections exist. After option addition, more than 10 RELA sections appear, including .rela.text and .rela.eh_frame. If -Wl,-q is not effective, when manual perf sampling and perf2bolt are performed or llvm-bolt is used to perform optimization (with or without sysboost), the alarm BOLT-WARNING: non-relocation mode for AArch64 is not fully supported is reported.

D-FOT Preparations

Install D-FOT using yum or build it from the source code using the following commands. (If libkperf or oeAware-manager is also built from the source code, you need to specify the library and include path when running cmake.)

shell

cd D-FOT
mkdir build && cd build
cmake ../ -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_SKIP_RPATH=TRUE
make -j`nproc`

cp build/libdfot.so /lib64/oeAware-plugin/
chmod 440 /lib64/oeAware-plugin/libdfot.so
mkdir -p /etc/dfot/
cp configs/dfot.ini /etc/dfot/

Configuration Modification

Modify /etc/dfot/dfot/ini. The configuration items can be set according to the following description. Public configuration: [general]

Configuration Item	Value Range	Available	Description
LOG_LEVEL	`<FATAL, ERROR, WARN, INFO, DEBUG>`	Yes	Log level for the optimization service. Lower levels produce more log output.
COLLECTOR_SAMPLING_STRATEGY	`<0>`	No	Sampling policy. `0` indicates that low-frequency sampling is continuously performed after the plugin is enabled. `1` indicates that the monitoring thread is started when the plugin is enabled. Sampling is performed only when the load reaches the threshold. Currently, the sampling process is controlled by oeAware, and only `0` is supported.
COLLECTOR_HIGH_LOAD_THRESHOLD	`[0, cpus*100]`	No	Application CPU usage threshold (`HIGH_LOAD_THRESHOLD`) for triggering sampling. This parameter is available only when sampling policy is set to `1`. Currently, this parameter is not supported.
COLLECTOR_DATA_AGING_TIME	Determined based on actual requirements	Yes	Aging time of sampling data, in milliseconds. When the time difference between the current data and the earliest data reaches the threshold, the accumulated sampling data is discarded.
TUNER_TOOL	`["sysboost"]`	No	Binary optimizer. Currently, only sysboost is supported.
TUNER_CHECK_PERIOD	`[10, max]`	Yes	Interval for optimization plugin check, in milliseconds. Sampling plugin data is collected at a specified interval to determine whether to perform optimization.
TUNER_PROFILE_DIR	Determined based on actual requirements	Yes	Location where the sampling data is stored. The profile file is named in format `[app_name]_[full_path_hash]_[threshold].profile`.
TUNER_OPTIMIZING_STRATEGY	`[0, 1]`	Yes	Optimization policy. `0` indicates that the optimization is performed only once, and `1` indicates that the optimization can be performed for multiple times as long as the sampling information is updated.
TUNER_OPTIMIZING_CONDITION	`[0, 2]`	No	Condition for triggering optimization. `0` indicates that the optimization starts immediately after the application exits. `1` indicates that the optimization is performed when the load is low. `2` indicates that the optimization is performed when the application exits and the load is low. Currently, only `0` is supported.

Application configuration: [app]

Configuration Item	Value Range	Available	Description
FULL_PATH	Determined based on actual requirements	Yes	Absolute path of the application binary file.
DEFAULT_PROFILE	Determined based on actual requirements	Yes	Default profile file of the application, which is used to enable binary optimization during cold start. If there is no such file, leave it empty.
COLLECTOR_DUMP_DATA_THRESHOLD	`[10000, max]`	Yes	Row count threshold for exporting sampling data to the profile. A larger value indicates more samples to be collected before the export occurs.
BOLT_DIR	N/A	No	BOLT tool path. If this parameter is left empty, the default value `/usr/bin` is used. `$\{BOLT_DIR}/perf2bolt` and `$\{BOLT_DIR}/llvm-bolt` are invoked internally. This parameter is determined by sysboost.
BOLT_OPTIONS	Determined based on actual requirements	Yes	BOLT optimization option. This option can be configured to override the built-in default option for specific optimization.
UPDATE_DEBUG_INFO	`[0, 1]`	Yes	Whether to update the debugging information synchronously during optimization. `1` indicates that the debugging information is updated, and `0` indicates that the debugging information is not updated. Note that updating the debugging information will take extra time.

Plugin Usage

See oeAware-manager.

Constraints

This feature can be used in container-based deployment scenarios. Optimization components such as D-FOT must be deployed outside the container.
The target application to be optimized must include relocation information.
When D-FOT is used as the oeAware tuning plugin, the fixed sampling frequency of the oeAware collection plugin pmu_sampling_collector is 100. This may cause a long sampling time. (For reference, the default sampling frequency of perf is 4000.)

Future Plans

[ ] Virtualization scenario improvement
[ ] Runtime optimization support
[ ] Enhanced binary optimization

D-FOT User Guide ​

Overview ​

Software Architecture Description ​

Dependency Items ​

Procedure ​

Prerequisites for Applications to Be Optimized ​

D-FOT Preparations ​

Configuration Modification ​

Plugin Usage ​

Constraints ​

Future Plans ​