Use much faster getcpu() via vDSO #424
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vDSO (virtual dynamic shared object) is exported by Linux kernel into every userspace program, designed to speed up this process for certain system calls. For Linux/x86_64, getcpu() can be called via vDSO, which makes getcpu() much faster. The faster getcpu() invocation is beneficial when retrieving NUMA node information. Benchmarking[1] on AMD Ryzen Threadripper 2990WX 32-Core Processor: getcpu: syscall: 103 nsec/call getcpu: vdso: 18 nsec/call We can not use dlsym to resolve the vDSO symbol "__vdso_getcpu" directly becase it would cause recursive malloc calls when MI_DEBUG_FULL is enabled. [1] https://github.com/nathanlynch/vdsotest Co-authored-by: Chin-Hao Lo <[email protected]> Signed-off-by: Jim Huang <[email protected]>
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@jserv noob question: why doesn't the default GLIBC getcpu() doesn't leverage vdso? |
In glibc development, |
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Thanks for your technical excellence :) |
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vDSO (virtual dynamic shared object) is exported by Linux kernel into every userspace program, designed to speed up this process for certain system calls. For Linux/x86_64, getcpu() can be called via vDSO, which
makes getcpu() much faster. The faster getcpu() invocation is beneficial when retrieving NUMA node information.
Benchmarking on AMD Ryzen Threadripper 2990WX 32-Core Processor: