Use sleep-aware monotonic clock if available

cmake/AwsFeatureTests.cmake

@@ -131,6 +131,64 @@ if(MSVC)
     }" AWS_HAVE_MSVC_INTRINSICS_X64)
 endif()
 
+if(NOT CMAKE_CROSSCOMPILING)
+    check_c_source_runs("
+        #include <stdint.h>
+        #include <time.h>
+
+        static const uint64_t NS_PER_SEC = 1000000000;
+
+        bool get_time(uint64_t *current_time) {
+            struct timespec ts;
+            if (clock_gettime(CLOCK_BOOTTIME, &ts)) {
+                return false;
+            }
+
+            uint64_t secs = (uint64_t)ts.tv_sec;
+            uint64_t n_secs = (uint64_t)ts.tv_nsec;
+            *current_time = (secs * NS_PER_SEC) + n_secs;
+
+            return true;
+        }
+
+        int main() {
+            uint64_t start_timestap = 0;
+            if (!get_time(&start_timestap)) {
+                return -1;
+            }
+
+            return 0;
+        }" AWS_HAS_POSIX_BOOT_CLOCK)
+else()
+    check_c_source_compiles("
+        #include <stdint.h>
+        #include <time.h>
+
+        static const uint64_t NS_PER_SEC = 1000000000;
+    
+        bool get_time(uint64_t *current_time) {
+            struct timespec ts;
+            if (clock_gettime(CLOCK_BOOTTIME, &ts)) {
+                return false;
+            }
+
+            uint64_t secs = (uint64_t)ts.tv_sec;
+            uint64_t n_secs = (uint64_t)ts.tv_nsec;
+            *current_time = (secs * NS_PER_SEC) + n_secs;
+
+            return true;
+        }
+
+        int main() {
+            uint64_t start_timestap = 0;
+            if (!get_time(&start_timestap)) {
+                return -1;
+            }
+
+            return 0;
+        }" AWS_HAS_POSIX_BOOT_CLOCK)
+endif()
+
 # This does a lot to detect when intrinsics are available and has to set cflags to do so.
 # leave it in its own file for ease of managing it.
 include(AwsSIMD)

include/aws/common/config.h.in

@@ -29,5 +29,6 @@
 #cmakedefine AWS_ARCH_INTEL
 #cmakedefine AWS_ARCH_INTEL_X64
 #cmakedefine AWS_USE_CPU_EXTENSIONS
+#cmakedefine AWS_HAS_POSIX_BOOT_CLOCK
 
 #endif

source/posix/clock.c

@@ -9,7 +9,9 @@
 
 static const uint64_t NS_PER_SEC = 1000000000;
 
-#if defined(CLOCK_MONOTONIC_RAW)
+#if defined(AWS_HAS_POSIX_BOOT_CLOCK)
+#    define HIGH_RES_CLOCK CLOCK_BOOTTIME
+#elif defined(CLOCK_MONOTONIC_RAW)
 #    define HIGH_RES_CLOCK CLOCK_MONOTONIC_RAW
 #else
 #    define HIGH_RES_CLOCK CLOCK_MONOTONIC