Fast memory test on Redis crash.

1 files changed, 31 insertions, 0 deletions

diff --git a/src/memtest.c b/src/memtest.c
index 56162ff4f..82da27c8b 100644
--- a/src/memtest.c
+++ b/src/memtest.c
@@ -35,6 +35,7 @@
 #include <errno.h>
 #include <termios.h>
 #include <sys/ioctl.h>
+#include "config.h"
 
 #if (ULONG_MAX == 4294967295UL)
 #define MEMTEST_32BIT
@@ -240,6 +241,36 @@ void memtest_test(size_t megabytes, int passes) {
     }
 }
 
+/* This is a fast O(N) best effort memory test, only ZERO-ONE tests and
+ * checkerboard tests are performed, without pauses between setting and
+ * reading the value, so this can only detect a subclass of permanent errors.
+ *
+ * However the function does not destroy the content of the memory tested that
+ * is left unmodified.
+ *
+ * If a memory error is detected, 1 is returned. Otherwise 0 is returned. */
+int memtest_non_destructive(void *addr, size_t size) {
+    volatile unsigned long *p = addr;
+    unsigned long val;
+    size_t j;
+
+    size /= sizeof(unsigned long);
+    for (j = 0; j < size; j++) {
+        val = p[j];
+
+        p[j] = 0; if (p[j] != 0) goto err;
+        p[j] = (unsigned long)-1; if (p[j] != (unsigned long)-1) goto err;
+        p[j] = ULONG_ONEZERO; if (p[j] != ULONG_ONEZERO) goto err;
+        p[j] = ULONG_ZEROONE; if (p[j] != ULONG_ZEROONE) goto err;
+        p[j] = val; /* restore the original value. */
+    }
+    return 0;
+
+err: /* memory error detected. */
+    p[j] = val;
+    return 1;
+}
+
 void memtest(size_t megabytes, int passes) {
     if (ioctl(1, TIOCGWINSZ, &ws) == -1) {
         ws.ws_col = 80;