Adjust memory allocation functions to allow sibling calls Many modern compilers are able to optimize function calls to functions where the parameters of the called function match a leading subset of the calling function's parameters. If there are no instructions in the calling function after the function is called, then the compiler is free to avoid any stack frame setup and implement the function call as a "jmp" rather than a "call". This is called sibling call optimization.
Here we adjust the memory allocation functions in mcxt.c to allow this optimization. This requires moving some responsibility into the memory context implementations themselves. It's now the responsibility of the MemoryContext to check for malloc failures. This is good as it both allows the sibling call optimization, but also because most small and medium allocations won't call malloc and just allocate memory to an existing block. That can't fail, so checking for NULLs in that case isn't required. Also, traditionally it's been the responsibility of palloc and the other allocation functions in mcxt.c to check for invalid allocation size requests. Here we also move the responsibility of checking that into the MemoryContext. This isn't to allow the sibling call optimization, but more because most of our allocators handle large allocations separately and we can just add the size check when doing large allocations. We no longer check this for non-large allocations at all. To make checking the allocation request sizes and ERROR handling easier, add some helper functions to mcxt.c for the allocators to use. Author: Andres Freund Reviewed-by: David Rowley Discussion: https://postgr.es/m/20210719195950.gavgs6ujzmjfa...@alap3.anarazel.de Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/743112a2e9938b98d716384fa9374c41afe74e41 Modified Files -------------- src/backend/utils/mmgr/alignedalloc.c | 11 +- src/backend/utils/mmgr/aset.c | 22 ++-- src/backend/utils/mmgr/generation.c | 17 +-- src/backend/utils/mmgr/mcxt.c | 229 ++++++++++++++-------------------- src/backend/utils/mmgr/slab.c | 11 +- src/include/nodes/memnodes.h | 42 ++++++- src/include/utils/memutils_internal.h | 30 +++-- 7 files changed, 196 insertions(+), 166 deletions(-)
