cds/os/linux/topology.h

   1 //$$CDS-header$$
   2
   3 #ifndef CDSLIB_OS_LINUX_TOPOLOGY_H
   4 #define CDSLIB_OS_LINUX_TOPOLOGY_H
   5
   6 #ifndef CDSLIB_OS_TOPOLOGY_H
   7 #   error "<cds/os/topology.h> must be included instead"
   8 #endif
   9
  10 #include <cds/details/defs.h>
  11 #include <cds/threading/model.h>
  12
  13 #include <sys/syscall.h>
  14 #include <sched.h>
  15
  16 namespace cds { namespace OS {
  17     /// Linux-specific wrappers
  18     CDS_CXX11_INLINE_NAMESPACE namespace Linux {
  19
  20         /// System topology
  21         /**
  22             The implementation assumes that processor IDs are in numerical order
  23             from 0 to N - 1, where N - count of processor in the system
  24         */
  25         struct topology {
  26         private:
  27             //@cond
  28             static unsigned int     s_nProcessorCount;
  29             //@endcond
  30         public:
  31
  32             /// Logical processor count for the system
  33             static unsigned int processor_count()
  34             {
  35                 return s_nProcessorCount;
  36             }
  37
  38             /// Get current processor number
  39             /**
  40                 Caveat: \p current_processor calls system \p sched_getcpu function
  41                 that may not be defined for target system (\p sched_getcpu is available since glibc 2.6).
  42                 If \p sched_getcpu is not defined the function emulates "current processor number" using
  43                 thread-specific data. You may manually disable the \p sched_getcpu usage compiling with
  44                 <tt>-DCDS_LINUX_NO_sched_getcpu</tt>.
  45             */
  46             static unsigned int current_processor()
  47             {
  48             // Compile libcds with -DCDS_LINUX_NO_sched_getcpu if your linux does not have sched_getcpu (glibc version less than 2.6)
  49 #           if !defined(CDS_LINUX_NO_sched_getcpu) && defined(SYS_getcpu)
  50                 int nProcessor = ::sched_getcpu();
  51                 return nProcessor == -1 ? 0 : (unsigned int) nProcessor;
  52 #           else
  53                 // Use fake "current processor number" assigned for current thread
  54                 return (unsigned int) threading::Manager::fake_current_processor();
  55
  56                 /*
  57                 Another way (for x86/amd64 only)
  58
  59                 Using cpuid and APIC ID (http://www.scss.tcd.ie/Jeremy.Jones/GetCurrentProcessorNumberXP.htm)
  60                 for x86 and amd64
  61                 {
  62                     _asm {mov eax, 1}
  63                     _asm {cpuid}
  64                     _asm {shr ebx, 24}
  65                     _asm {mov eax, ebx}
  66                 }
  67                 However:
  68                     - cpuid is full sync barrier
  69                     - it is only for x86/amd64 architecture
  70                 */
  71 #           endif
  72             }
  73
  74             /// Synonym for \ref current_processor
  75             static unsigned int native_current_processor()
  76             {
  77                 return current_processor();
  78             }
  79
  80             //@cond
  81             static void init();
  82             static void fini();
  83             //@endcond
  84         };
  85     }   // namespace Linux
  86
  87 #ifndef CDS_CXX11_INLINE_NAMESPACE_SUPPORT
  88     using Linux::topology;
  89 #endif
  90 }}  // namespace cds::OS
  91
  92 #endif  // #ifndef CDSLIB_OS_LINUX_TOPOLOGY_H