erts: Add power saving cpu feature tests and use them

3 files changed, 69 insertions, 26 deletions

diff --git a/erts/emulator/sys/unix/sys_time.c b/erts/emulator/sys/unix/sys_time.c
index 9738a8c352..03d39c7ce6 100644
--- a/erts/emulator/sys/unix/sys_time.c
+++ b/erts/emulator/sys/unix/sys_time.c
@@ -971,18 +971,18 @@ static ErtsSysPerfCounter calculate_perf_counter_unit(void) {
 static int have_rdtscp(void)
 {
 #if defined(ETHR_X86_RUNTIME_CONF__)
-    /* On early x86 cpu's the tsc varies with
-       the current speed of the cpu, which means that the time per
-       tick vary depending on the current load of the cpu. We do not
-       want this as it would give very scewed numbers when the cpu is
-       mostly idle.
-       If we have the rdtscp feature it is a sign that the cpu is
-       relatively modern, and thus the tsc quite stable so we use it then.
+    /* On early x86 cpu's the tsc varies with the current speed of the cpu,
+       which means that the time per tick vary depending on the current
+       load of the cpu. We do not want this as it would give very scewed
+       numbers when the cpu is mostly idle.
+       The linux kernel seems to think that checking for constant and
+       reliable is enough to trust the counter so we do the same.
 
        If this test is not good enough, I don't know what we'll do.
        Maybe fallback on erts_sys_hrtime always, but that would be a shame as
        rdtsc is about 3 times faster than hrtime... */
-    return ETHR_X86_RUNTIME_CONF_HAVE_RDTSCP__;
+    return ETHR_X86_RUNTIME_CONF_HAVE_CONSTANT_TSC__ &&
+        ETHR_X86_RUNTIME_CONF_HAVE_TSC_RELIABLE__;
 #else
     return 0;
 #endif
diff --git a/erts/include/internal/ethread.h b/erts/include/internal/ethread.h
index 9956473057..e5c5cdfa33 100644
--- a/erts/include/internal/ethread.h
+++ b/erts/include/internal/ethread.h
@@ -274,18 +274,40 @@ ETHR_PROTO_NORETURN__ ethr_fatal_error__(const char *file,
      || (defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_AMD64))))
 #  define ETHR_X86_RUNTIME_CONF__
 
-#  define ETHR_X86_RUNTIME_CONF_HAVE_DW_CMPXCHG__ \
-  (__builtin_expect(ethr_runtime__.conf.have_dw_cmpxchg != 0, 1))
-#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_DW_CMPXCHG__ \
-  (__builtin_expect(ethr_runtime__.conf.have_dw_cmpxchg == 0, 0))
-#  define ETHR_X86_RUNTIME_CONF_HAVE_SSE2__ \
-  (__builtin_expect(ethr_runtime__.conf.have_sse2 != 0, 1))
-#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_SSE2__ \
-  (__builtin_expect(ethr_runtime__.conf.have_sse2 == 0, 0))
-#  define ETHR_X86_RUNTIME_CONF_HAVE_RDTSCP__ \
-  (__builtin_expect(ethr_runtime__.conf.have_rdtscp != 0, 1))
-#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_RDTSCP__ \
-  (__builtin_expect(ethr_runtime__.conf.have_rdtscp == 0, 0))
+#  define ETHR_X86_RUNTIME_CONF_HAVE_META(feature)              \
+    (__builtin_expect(ethr_runtime__.conf.have_##feature != 0, 1))
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_META(feature)           \
+    (__builtin_expect(ethr_runtime__.conf.have_##feature == 0, 0))
+
+#  define ETHR_X86_RUNTIME_CONF_HAVE_DW_CMPXCHG__       \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(dw_cmpxchg)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_DW_CMPXCHG__    \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(dw_cmpxchg)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_SSE2__     \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(sse2)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_SSE2__  \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(sse2)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_RDTSCP__   \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(rdtscp)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_RDTSCP__        \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(rdtscp)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_CONSTANT_TSC__     \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(constant_tsc)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_CONSTANT_TSC__   \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(nonstop_tsc)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NONSTOP_TSC__     \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(nonstop_tsc)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_NONSTOP_TSC__   \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(nonstop_tsc)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_TSC_RELIABLE__     \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(tsc_reliable)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_TSC_RELIABLE_TSC__   \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(tsc_reliable)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NONSTOP_TSC_S3__     \
+    ETHR_X86_RUNTIME_CONF_HAVE_META(nonstop_tsc_s3)
+#  define ETHR_X86_RUNTIME_CONF_HAVE_NO_NONSTOP_TSC_S3__        \
+    ETHR_X86_RUNTIME_CONF_HAVE_NO_META(nonstop_tsc_s3)
+
 #endif
 
 #if (defined(__GNUC__) \
@@ -305,6 +327,10 @@ typedef struct {
     int have_dw_cmpxchg;
     int have_sse2;
     int have_rdtscp;
+    int have_constant_tsc;
+    int have_tsc_reliable;
+    int have_nonstop_tsc;
+    int have_nonstop_tsc_s3;
 #endif
 #if defined(ETHR_PPC_RUNTIME_CONF__)
     int have_lwsync;
diff --git a/erts/lib_src/common/ethr_aux.c b/erts/lib_src/common/ethr_aux.c
index fbd870c2b5..3e7aad16c7 100644
--- a/erts/lib_src/common/ethr_aux.c
+++ b/erts/lib_src/common/ethr_aux.c
@@ -144,16 +144,33 @@ x86_init(void)
     eax = 0x80000000;
     ethr_x86_cpuid__(&eax, &ebx, &ecx, &edx);
 
-    if (eax >= 0x80000001) {
-        /* Get the extended feature set */
-        eax = 0x80000001;
+    if (eax < 0x80000001)
+        return;
+
+    if (eax >= 0x80000007) {
+        /* Advanced Power Management Information */
+        eax = 0x80000007;
 	ethr_x86_cpuid__(&eax, &ebx, &ecx, &edx);
-    } else {
-        eax = ebx = ecx = edx = 0;
+
+        /* I got the values below from:
+           http://lxr.free-electrons.com/source/arch/x86/include/asm/cpufeature.h
+           They can be gotten from the intel/amd manual as well.
+        */
+
+        ethr_runtime__.conf.have_constant_tsc  = (edx & (1 <<  8));
+        ethr_runtime__.conf.have_tsc_reliable   = (edx & (1 << 23));
+        ethr_runtime__.conf.have_nonstop_tsc    = (edx & (1 << 24));
+        ethr_runtime__.conf.have_nonstop_tsc_s3 = (edx & (1 << 30));
+
     }
-    
+
+    /* Extended Processor Info and Feature Bits */
+    eax = 0x80000001;
+    ethr_x86_cpuid__(&eax, &ebx, &ecx, &edx);
+
     /* bit 27 of edx is set if we have rdtscp */
     ethr_runtime__.conf.have_rdtscp = (edx & (1 << 27));
+
 }
 
 #endif /* ETHR_X86_RUNTIME_CONF__ */