8b2c2a596d
Summary: Add support for C++17 over-aligned allocation: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0035r4.html Supporting all 10 operators means we avoid thunking thru libstdc++-v3/libsupc++ and just call jemalloc directly. It's also worth noting that there is now an aligned *and sized* operator delete: ``` void operator delete(void* ptr, std::size_t size, std::align_val_t al) noexcept; ``` If JeMalloc did not provide this, the default implementation would ignore the size parameter entirely: https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/libsupc%2B%2B/del_opsa.cc#L30-L33 (I must also update ax_cxx_compile_stdcxx.m4 to a newer version with C++17 support.) Test Plan: Wrote a simple test that allocates and then deletes an over-aligned type: ``` struct alignas(32) Foo {}; Foo *f; int main() { f = new Foo; delete f; } ``` Before this change, both new and delete go thru PLT, and we end up calling regular old free: ``` (gdb) disassemble Dump of assembler code for function main(): ... 0x00000000004029b7 <+55>: call 0x4022d0 <_ZnwmSt11align_val_t@plt> ... 0x00000000004029d5 <+85>: call 0x4022e0 <_ZdlPvmSt11align_val_t@plt> ... (gdb) s free (ptr=0x7ffff6408020) at /home/engshare/third-party2/jemalloc/master/src/jemalloc.git-trunk/src/jemalloc.c:2842 2842 if (!free_fastpath(ptr, 0, false)) { ``` After this change, we directly call new/delete and ultimately call sdallocx: ``` (gdb) disassemble Dump of assembler code for function main(): ... 0x0000000000402b77 <+55>: call 0x496ca0 <operator new(unsigned long, std::align_val_t)> ... 0x0000000000402b95 <+85>: call 0x496e60 <operator delete(void*, unsigned long, std::align_val_t)> ... (gdb) s 116 je_sdallocx_noflags(ptr, size); ``` |
||
|---|---|---|
| bin | ||
| build-aux | ||
| doc | ||
| include | ||
| m4 | ||
| msvc | ||
| scripts | ||
| src | ||
| test | ||
| .appveyor.yml | ||
| .autom4te.cfg | ||
| .cirrus.yml | ||
| .gitattributes | ||
| .gitignore | ||
| .travis.yml | ||
| autogen.sh | ||
| ChangeLog | ||
| config.stamp.in | ||
| configure.ac | ||
| COPYING | ||
| INSTALL.md | ||
| jemalloc.pc.in | ||
| Makefile.in | ||
| README | ||
| run_tests.sh | ||
| TUNING.md | ||
jemalloc is a general purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support. jemalloc first came into use as the FreeBSD libc allocator in 2005, and since then it has found its way into numerous applications that rely on its predictable behavior. In 2010 jemalloc development efforts broadened to include developer support features such as heap profiling and extensive monitoring/tuning hooks. Modern jemalloc releases continue to be integrated back into FreeBSD, and therefore versatility remains critical. Ongoing development efforts trend toward making jemalloc among the best allocators for a broad range of demanding applications, and eliminating/mitigating weaknesses that have practical repercussions for real world applications. The COPYING file contains copyright and licensing information. The INSTALL file contains information on how to configure, build, and install jemalloc. The ChangeLog file contains a brief summary of changes for each release. URL: http://jemalloc.net/