Abhinav's work on usemem_ksm_hugepages.c

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/usemem_ksm_hugepages.c b/usemem_ksm_hugepages.c
new file mode 100644
index 0000000..4a0a753
--- /dev/null
+++ b/usemem_ksm_hugepages.c
@@ -0,0 +1,78 @@
+/*
+ * usemem.c exercises the ksm.c file in the mm for hugepages
+ *
+ * It takes one argument 'size' and mmaps anonymous memory of 'size'
+ *
+ * into the process virtual address space. The allocated memory is made mergeable
+ *
+ * to make ksm scan it. The MADV_HUGEPAGE flag makes sure that the pages are hugepages
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#define SLEEP_TIME	60
+
+void usage(char *name)
+{
+	fprintf(stderr, "usage: %s SIZE\n", name);
+	exit(1);
+}
+
+/* calls madvise with the the specified flag */
+
+void call_madvise(unsigned char *pointer_to_address, unsigned long size, int advise)
+{
+	if ((madvise(pointer_to_address, size, advise)) == -1) {
+		fprintf(stderr, "madvise failed with error : %s\n", strerror(errno));
+		munmap(pointer_to_address, size);
+		exit(1);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	if (argc != 2) usage(argv[0]);
+
+	unsigned long size = atoi(argv[1]);
+
+	unsigned char *p;
+
+	char command[50];
+
+	p = mmap(NULL, size, PROT_READ|PROT_WRITE,
+		  MAP_POPULATE|MAP_ANON|MAP_PRIVATE, -1, 0);
+
+	if (p == MAP_FAILED) {
+		fprintf(stderr, "anon  mmap failed: %s\n", strerror(errno));
+		exit(1);
+	}
+
+	/* collapse the pages into hugepages */
+	call_madvise(p, size, MADV_HUGEPAGE);
+
+	/* wait for hugepages to be allocated */
+	sleep(30);
+
+	/* make pages mergeable advised */
+	call_madvise(p, size, MADV_MERGEABLE);
+
+	sleep(30);
+
+	/* Turn off ksm and unmerge shared memory */
+	sprintf(command, "echo 2 > /sys/kernel/mm/ksm/run");
+
+	system(command);
+
+	/* make pages unmergeable */
+	call_madvise(p, size, MADV_UNMERGEABLE);
+
+	/* unmap mapping */
+	munmap(p, size);
+	return 0;
+
+}