processing optimizations Vasiliki (Vasia) Kalavri vkalavri@bu.edu ## Topics covered in this lecture • Costs of streaming operator execution • state, parallelism, selectivity • Dataflow optimizations • plan plan translation alternatives • Runtime optimizations • load management, scheduling, state management • Optimization semantics, correctness, profitability ## Revisiting the basics ## dataflow graph optimization be applied during runtime or does it have to be applied statically? ## Catalog of Optimizations ## Operator re-ordering ![Image](/uploads/documents/d/f/8/d/df8d9a883a0b9bacb2db614d10387ee7/p15_1

2022.3 Go 1.18 泛型落地 2022.8 Go 1.19 修订Go内存模型文档、支持Soft memory limit 2023.3 Go 1.20 引入Profile-Guided Optimizations Since Go 1.20… ’ alt=‘OCR图片’/> 提示 本Slide中的代码可以在https://go.dev/play/上体验 Go dev branch int https://github.com/golang/go/issues/59488 ’ alt=‘OCR图片’/> 第四部分 Compiler ’ alt=‘OCR图片’/> Profile-guided optimization默认开启 Go 1.21：默认-pgo=auto ’ alt=‘OCR图片’/> 第五部分 Tools ’ alt=‘OCR图片’/> Go version

The volatile qualifier is a vital tool for preventing compilers from performing certain harmful optimizations. ■ Unfortunately, many C++ programmers aren’t clear on exactly what protections volatile provides programmers apply the volatile qualifier incorrectly. ■ A misapplied volatile might: • prevent optimizations unnecessarily, or worse • fail to provide the expected protection, leading to subtle run-time operation. • Reading from a receive buffer may set or clear bits in a status register. ■ Compiler optimizations might change the number of register accesses. • Eliminating an access eliminates its side effects

compiler on Linux. GCC for openEuler inherits capabilities of the open source GCC. It also has optimizations on C, C++, and Fortran languages and delivers enhanced features such as automatic feedback-directed Concurrency and Ultimate Performance ## Feature 2: End-to-end FDO Major FDO technologies include profile-guided optimization (PGO) and AutoFDO, which work during compilation, along with BOLT, which works during

compiler (the :meta mechanism) ..... 1854 105.11 SubArrays ..... 1855 105.12 isbits Union Optimizations ..... 1859 105.13 System Image Building ..... 1860 105.14 Package Images ..... 1862 105 declare these fields as such using const as shown below. This enables some, but not all of the optimizations of immutable structs, and can be used to enforce invariants on the particular fields marked as if the compiler could not determine that the regex object was constant over all loops, certain optimizations might not be possible, making this version still less efficient than the more convenient literal

compiler (the :meta mechanism) ..... 1854 105.11 SubArrays ..... 1855 105.12 isbits Union Optimizations ..... 1859 105.13 System Image Building ..... 1860 105.14 Package Images ..... 1862 105 declare these fields as such using const as shown below. This enables some, but not all of the optimizations of immutable structs, and can be used to enforce invariants on the particular fields marked as if the compiler could not determine that the regex object was constant over all loops, certain optimizations might not be possible, making this version still less efficient than the more convenient literal

compiler (the :meta mechanism) ..... 1854 105.11 SubArrays ..... 1855 105.12 isbits Union Optimizations ..... 1859 105.13 System Image Building ..... 1860 105.14 Package Images ..... 1862 105 declare these fields as such using const as shown below. This enables some, but not all of the optimizations of immutable structs, and can be used to enforce invariants on the particular fields marked as if the compiler could not determine that the regex object was constant over all loops, certain optimizations might not be possible, making this version still less efficient than the more convenient literal

Talking to the compiler (the :meta mechanism) 1837 104.11 SubArrays 1838 104.12 isbits Union Optimizations 1842 104.13 System Image Building 1843 104.14 Package Images 1845 104.15 Custom LLVM Passes declare these fields as such using const as shown below. This enables some, but not all of the optimizations of immutable structs, and can be used to enforce invariants on the particular fields marked as if the compiler could not determine that the regex object was constant over all loops, certain optimizations might not be possible, making this version still less efficient than the more convenient literal

Talking to the compiler (the :meta mechanism) 1835 104.11 SubArrays 1836 104.12 isbits Union Optimizations 1840 104.13 System Image Building 1841 104.14 Package Images 1843 104.15 Custom LLVM Passes declare these fields as such using const as shown below. This enables some, but not all of the optimizations of immutable structs, and can be used to enforce invariants on the particular fields marked as if the compiler could not determine that the regex object was constant over all loops, certain optimizations might not be possible, making this version still less efficient than the more convenient literal

notes ..... 33 1.2.57 $OBJECTCHECKS : Check Object ..... 34 1.2.58 $OPTIMIZATION : Enable Optimizations ..... 34 1.2.59 $PACKENUM or $Z : Minimum enumeration type size ..... 36 1.2.60 $PACKRECORDS Select mode features ..... 50 1.3.23 $N : Numeric processing ..... 51 1.3.24 $O : Level 2 Optimizations ..... 51 1.3.25 $OBJECTPATH : Specify object path ..... 52 1.3.26 $P or $OPENSTRINGS : Use 10.2 Programming threads 123 10.3 Critical sections 126 10.4 The Thread Manager 127 11 Optimizations 129 11.1 Non processor specific 129 11.1.1 Constant folding 129 11.1.2 Constant merging