folly::Getcpu Struct Reference

#include <CacheLocality.h>

Public Types
typedef int(*	Func) (unsigned *cpu, unsigned *node, void *unused)
	Function pointer to a function with the same signature as getcpu(2). More...

Static Public Member Functions
static Func	resolveVdsoFunc ()

Detailed Description

Knows how to derive a function pointer to the VDSO implementation of getcpu(2), if available

Definition at line 122 of file CacheLocality.h.

Member Typedef Documentation

typedef int(* folly::Getcpu::Func) (unsigned *cpu, unsigned *node, void *unused)

Function pointer to a function with the same signature as getcpu(2).

Definition at line 124 of file CacheLocality.h.

Member Function Documentation

Getcpu::Func folly::Getcpu::resolveVdsoFunc ( )

static

Returns a pointer to the VDSO implementation of getcpu(2), if available, or nullptr otherwise. This function may be quite expensive, be sure to cache the result.

Definition at line 208 of file CacheLocality.cpp.

References h.

Referenced by folly::AccessSpreader< Atom >::pickGetcpuFunc(), and TEST().

                                   {
#if !FOLLY_HAVE_LINUX_VDSO
  return nullptr;
#else
  void* h = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  if (h == nullptr) {
    return nullptr;
  }

  auto func = Getcpu::Func(dlsym(h, "__vdso_getcpu"));
  if (func == nullptr) {
    // technically a null result could either be a failure or a successful
    // lookup of a symbol with the null value, but the second can't actually
    // happen for this symbol.  No point holding the handle forever if
    // we don't need the code
    dlclose(h);
  }

  return func;
#endif
}

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The documentation for this struct was generated from the following files:

• proxygen/folly/folly/concurrency/CacheLocality.h
• proxygen/folly/folly/concurrency/CacheLocality.cpp