Merge pull request #10721 from p12tic:expose-fake-cpuinfo-cache

PiperOrigin-RevId: 660077238

pkg/cpuid/cpuid_amd64.go

@@ -308,7 +308,7 @@ func (fs FeatureSet) HasFeature(feature Feature) bool {
 
 // WriteCPUInfoTo is to generate a section of one cpu in /proc/cpuinfo. This is
 // a minimal /proc/cpuinfo, it is missing some fields like "microcode" that are
-// not always printed in Linux. The bogomips field is simply made up.
+// not always printed in Linux. Several fields are simply made up.
 func (fs FeatureSet) WriteCPUInfoTo(cpu, numCPU uint, w io.Writer) {
 	// Avoid many redundant calls here, since this can occasionally appear
 	// in the hot path. Read all basic information up front, see above.
@@ -322,6 +322,13 @@ func (fs FeatureSet) WriteCPUInfoTo(cpu, numCPU uint, w io.Writer) {
 	fmt.Fprintf(w, "model name\t: %s\n", "unknown") // Unknown for now.
 	fmt.Fprintf(w, "stepping\t: %s\n", "unknown")   // Unknown for now.
 	fmt.Fprintf(w, "cpu MHz\t\t: %.3f\n", cpuFreqMHz)
+	// Pretend the CPU has 8192 KB of cache. Note that real /proc/cpuinfo exposes total L3 cache
+	// size on Intel and per-core L2 cache size on AMD (as of Linux 6.1.0), so the value of this
+	// field is not really important in practice. Any value that is chosen here will be wrong
+	// by an order of magnitude on a significant chunk of x86 machines.
+	// 8192 KB is selected because it is a reasonable size that will be effectively usable on
+	// lightly loaded machines - most machines have 1-4MB of L3 cache per core.
+	fmt.Fprintf(w, "cache size\t: 8192 KB\n")
 	fmt.Fprintf(w, "physical id\t: 0\n") // Pretend all CPUs are in the same socket.
 	fmt.Fprintf(w, "siblings\t: %d\n", numCPU)
 	fmt.Fprintf(w, "core id\t\t: %d\n", cpu)

test/syscalls/linux/proc.cc

@@ -125,28 +125,14 @@ namespace {
 // fields that are printed conditionally, but are present on common
 // configurations (e.g. when CONFIG_SMP is set).
 static const char* required_fields[] = {
-    "processor",
-    "vendor_id",
-    "cpu family",
-    "model\t\t:",
-    "model name",
-    "stepping",
-    "cpu MHz",
-    "physical id",
-    "siblings",
-    "core id",
-    "cpu cores",
-    "apicid\t\t:",
-    "initial apicid",
-    "fpu\t\t:",
-    "fpu_exception",
-    "cpuid level",
-    "wp",
-    "bogomips",
-    "clflush size",
-    "cache_alignment",
-    "address sizes",
-    "power management",
+    "processor",     "vendor_id",        "cpu family",
+    "model\t\t:",    "model name",       "stepping",
+    "cpu MHz",       "cache size",       "physical id",
+    "siblings",      "core id",          "cpu cores",
+    "apicid\t\t:",   "initial apicid",   "fpu\t\t:",
+    "fpu_exception", "cpuid level",      "wp",
+    "bogomips",      "clflush size",     "cache_alignment",
+    "address sizes", "power management",
 };
 #elif defined(__aarch64__)
 // This list of "required" fields is taken from reading the file