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diff --git a/ACE/apps/soreduce/README b/ACE/apps/soreduce/README new file mode 100644 index 00000000000..5e0264bdab2 --- /dev/null +++ b/ACE/apps/soreduce/README @@ -0,0 +1,163 @@ +Shared Library Reduction Tool +----------------------------- + +The motivation for this tool was the understanding that the ACE & TAO +libraries were to be linked with the VxWorks kernel to allow multiple +applications to be run simultaniously with a minimum of footprint +consumed. Ordinarily a choice is made between static linking +applications, where each application gets only the object modules +needed, and shared object linkage, where multiple applications share +access to full libraries. Frequently a shared library will contain +code and data which is not used by any of the applications in a +particular configuration. The Shared Library Reduction Tool builds +libraries that include only the modules needed to support a specified +set of applications. + +The analysis is performed very late in the application implementation, +allowing the system implementors the freedom to use whatever TAO & ACE +components are needed. Once an application is built and running, its +shared object need may be evaluated. The evaluation is straight +forward. Run the soreduce program, passing the path to all of the +applications that will share the libraries. The soreduce program uses +the following steps to generate its results. + +1. A list of undefined symbols and shared libraries is built by + invoking the ldd and nm commands on each application. For now, + soreduce assumes the GNU variant of these tools. + +2. For each shared library, soreduce tries to invoke nm on each of the + intermediate object files used to build the library. It is + important that target library directory has a current .shobj + subdirectory. + +3. The list of undefined symbols is traversed. For each entry in the list, the + modules loaded from step 2 are examined to look for a matching + symbol. When one is found, the target symbol, and any others + satisfied by the module are removed from the list, and any + undefined symbols in the module are added to the list. This + process is repeated until the entire list of undefined symbols is + traversed without change. + +4. MPC files are generated. Rather than invoking the linker directly, an mpc + file is generated that may be used to build the libs. With these + mpc files, the actual library will be named (orig)_subset. + +Analysis Artifacts +------------------ + +Development of the shared library reduction tool also provided a +secondary benefit. It is able to output usage metrics for the various +modules, which may be useful for directing further hand-crafted +reduction efforts. Using the GNU nm with more verbose output, it is +possible to determine the first function using a given undefined +symbol. While it is not (yet) possible to automate the refactoring of +code based on this analysis, this information can provide a road map +for breaking a single module into two or a few that will result in +fewer incidental dependancies overall. However this speculation has +not been tested. + +Test results +------------ + +Running soreduce providing itself as the sole client. The soreduce +application is built on top of ACE, using just a few of ACE's +features. Here is the output: + +bash$ ./soreduce soreduce +discovering libraries +loading object modules +Libs subject to analysis: + ACE +Starting analysis +pass 0, undef count = 69 +pass 1, undef count = 207 +pass 2, undef count = 278 +pass 3, undef count = 271 +pass 4, undef count = 245 +pass 5, undef count = 235 +Writing results +Making directory /opt/wustl/ACE_wrappers/build/native/ace/usage_metrics +ACE: 61 out of 210 modules required +writing file /opt/wustl/ACE_wrappers/build/native/ace/ACE_subset.mpc +Done. + +The size of libACE.so before rebuilding: + +bash$ size libACE.so + text data bss dec hex filename +2361958 498760 12516 2873234 2bd792 libACE.so + +and after: + +bash$ size libACE_subset.so + text data bss dec hex filename + 987167 207452 7580 1202199 125817 libACE_subset.so + + +2873234 - 1202199 = 1671035 bytes eliminated, a 58.2% reduction + +Here is another example, using the Naming Service, and its simple test +client. Note that the orbsvcs results are bogus, the libraries are +already fairly well factored so that the additional subsetting by +soreduce is not effective. Also, due to the layout of the orbsvcs +library source directory, the tool may not generate valid mpc files. + +bash$ $ACE_ROOT/apps/soreduce/soreduce Naming_Service/Naming_Service tests/Simple_Naming/client +discovering libraries +loading object modules +Libs subject to analysis: + TAO_CosNaming + TAO_Svc_Utils + TAO_IORTable + TAO_PortableServer + TAO + ACE +Starting analysis +pass 0, undef count = 339 +pass 1, undef count = 580 +pass 2, undef count = 438 +pass 3, undef count = 278 +pass 4, undef count = 244 +pass 5, undef count = 246 +pass 6, undef count = 242 +Writing results +Making directory /opt/wustl/ACE_wrappers/build/native/TAO/orbsvcs/orbsvcs/usage_metrics +TAO_CosNaming: 11 out of 256 modules required +writing file /opt/wustl/ACE_wrappers/build/native/TAO/orbsvcs/orbsvcs/TAO_CosNaming_subset.mpc +Making directory /opt/wustl/ACE_wrappers/build/native/TAO/orbsvcs/orbsvcs/usage_metrics +TAO_Svc_Utils: 8 out of 256 modules required +writing file /opt/wustl/ACE_wrappers/build/native/TAO/orbsvcs/orbsvcs/TAO_Svc_Utils_subset.mpc +Making directory /opt/wustl/ACE_wrappers/build/native/TAO/tao/IORTable/usage_metrics +TAO_IORTable: 4 out of 4 modules required +writing file /opt/wustl/ACE_wrappers/build/native/TAO/tao/IORTable/TAO_IORTable_subset.mpc +Making directory /opt/wustl/ACE_wrappers/build/native/TAO/tao/PortableServer/usage_metrics +TAO_PortableServer: 26 out of 29 modules required +writing file /opt/wustl/ACE_wrappers/build/native/TAO/tao/PortableServer/TAO_PortableServer_subset.mpc +Making directory /opt/wustl/ACE_wrappers/build/native/TAO/tao/usage_metrics +TAO: 160 out of 191 modules required +writing file /opt/wustl/ACE_wrappers/build/native/TAO/tao/TAO_subset.mpc +Making directory /opt/wustl/ACE_wrappers/build/native/ace/usage_metrics +ACE: 75 out of 210 modules required +writing file /opt/wustl/ACE_wrappers/build/native/ace/ACE_subset.mpc +Done. + +Size before & after: + text data bss dec hex filename +2361958 498760 12516 2873234 2bd792 libACE.so +3432206 704188 30992 4167386 3f96da libTAO.so +1931145 326632 7528 2265305 2290d9 libTAO_PortableServer.so + 76561 12504 364 89429 15d55 libTAO_IORTable.so + + +Sum: 9395354 + + + text data bss dec hex filename +1340017 275440 8140 1623597 18c62d libACE_subset.so +3131226 643816 27984 3803026 3a0792 libTAO_subset.so +1845515 308812 6896 2161223 20fa47 libTAO_PortableServer_subset.so + 76603 12508 364 89475 15d83 libTAO_IORTable_subset.so + +Sum: 7677321 + +Savings: 1718033 or 18.3% |