diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index 51f7ce9..8c1e7ec 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -62,6 +62,28 @@
 __BIONIC_WEAK_VARIABLE_FOR_NATIVE_BRIDGE
 const char* __progname;
 
+#if defined(__i386__) || defined(__x86_64__)
+// Default sizes based on the old hard-coded values for Atom/Silvermont (x86) and Core 2 (x86-64)...
+size_t __x86_data_cache_size = 24 * 1024;
+size_t __x86_data_cache_size_half = __x86_data_cache_size / 2;
+size_t __x86_shared_cache_size = sizeof(long) == 8 ? 4096 * 1024 : 1024 * 1024;
+size_t __x86_shared_cache_size_half = __x86_shared_cache_size / 2;
+// ...overwritten at runtime based on the cpu's reported cache sizes.
+static void __libc_init_x86_cache_info() {
+  // Handle the case where during early boot /sys fs may not yet be ready,
+  // resulting in sysconf() returning 0, leading to crashes.
+  // In that case (basically just init), we keep the defaults.
+  if (sysconf(_SC_LEVEL1_DCACHE_SIZE) != 0) {
+    __x86_data_cache_size = sysconf(_SC_LEVEL1_DCACHE_SIZE);
+    __x86_data_cache_size_half = __x86_data_cache_size / 2;
+  }
+  if (sysconf(_SC_LEVEL2_CACHE_SIZE) != 0) {
+    __x86_shared_cache_size = sysconf(_SC_LEVEL2_CACHE_SIZE);
+    __x86_shared_cache_size_half = __x86_shared_cache_size / 2;
+  }
+}
+#endif
+
 void __libc_init_globals() {
   // Initialize libc globals that are needed in both the linker and in libc.
   // In dynamic binaries, this is run at least twice for different copies of the
@@ -171,6 +193,10 @@
   __system_properties_init(); // Requires 'environ'.
   __libc_init_fdsan(); // Requires system properties (for debug.fdsan).
   __libc_init_fdtrack();
+
+#if defined(__i386__) || defined(__x86_64__)
+  __libc_init_x86_cache_info();
+#endif
 }
 
 void __libc_init_fork_handler() {