Test compaction of mlocked memory

Commit commit 5bbe3547aa3b ("mm: allow compaction of unevictable pages")
introduced a sysctl that allows userspace to enable scanning of locked
pages for compaction.  This patch introduces a new test which fragments
main memory and attempts to allocate a number of huge pages to exercise
this compaction logic.

Tested on machines with up to 32 GB RAM. With the patch a much larger
number of huge pages can be allocated than on the kernel without the
patch.

Example output:
On a machine with 16 GB RAM:
sudo make run_tests vm
...
-----------------------
running compaction_test
-----------------------
No of huge pages allocated = 3834
[PASS]
...

Signed-off-by: Sri Jayaramappa <sjayaram@akamai.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-api@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric B Munson <emunson@akamai.com>
Reviewed-by: Eric B Munson <emunson@akamai.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

3 files changed, 243 insertions, 1 deletions

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index a5ce9534eb15..231b9a031f6a 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -1,7 +1,12 @@
 # Makefile for vm selftests
 
 CFLAGS = -Wall
-BINARIES = hugepage-mmap hugepage-shm map_hugetlb thuge-gen hugetlbfstest
+BINARIES = compaction_test
+BINARIES += hugepage-mmap
+BINARIES += hugepage-shm
+BINARIES += hugetlbfstest
+BINARIES += map_hugetlb
+BINARIES += thuge-gen
 BINARIES += transhuge-stress
 
 all: $(BINARIES)
diff --git a/tools/testing/selftests/vm/compaction_test.c b/tools/testing/selftests/vm/compaction_test.c
new file mode 100644
index 000000000000..932ff577ffc0
--- /dev/null
+++ b/tools/testing/selftests/vm/compaction_test.c
@@ -0,0 +1,225 @@
+/*
+ *
+ * A test for the patch "Allow compaction of unevictable pages".
+ * With this patch we should be able to allocate at least 1/4
+ * of RAM in huge pages. Without the patch much less is
+ * allocated.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+
+#define MAP_SIZE 1048576
+
+struct map_list {
+        void *map;
+        struct map_list *next;
+};
+
+int read_memory_info(unsigned long *memfree, unsigned long *hugepagesize)
+{
+        char  buffer[256] = {0};
+        char *cmd = "cat /proc/meminfo | grep -i memfree | grep -o '[0-9]*'";
+        FILE *cmdfile = popen(cmd, "r");
+
+        if (!(fgets(buffer, sizeof(buffer), cmdfile))) {
+                perror("Failed to read meminfo\n");
+                return -1;
+        }
+
+        pclose(cmdfile);
+
+        *memfree = atoll(buffer);
+        cmd = "cat /proc/meminfo | grep -i hugepagesize | grep -o '[0-9]*'";
+        cmdfile = popen(cmd, "r");
+
+        if (!(fgets(buffer, sizeof(buffer), cmdfile))) {
+                perror("Failed to read meminfo\n");
+                return -1;
+        }
+
+        pclose(cmdfile);
+        *hugepagesize = atoll(buffer);
+
+        return 0;
+}
+
+int prereq(void)
+{
+        char allowed;
+        int fd;
+
+        fd = open("/proc/sys/vm/compact_unevictable_allowed",
+                  O_RDONLY | O_NONBLOCK);
+        if (fd < 0) {
+                perror("Failed to open\n"
+                       "/proc/sys/vm/compact_unevictable_allowed\n");
+                return -1;
+        }
+
+        if (read(fd, &allowed, sizeof(char)) != sizeof(char)) {
+                perror("Failed to read from\n"
+                       "/proc/sys/vm/compact_unevictable_allowed\n");
+                close(fd);
+                return -1;
+        }
+
+        close(fd);
+        if (allowed == '1')
+                return 0;
+
+        return -1;
+}
+
+int check_compaction(unsigned long mem_free, unsigned int hugepage_size)
+{
+        int fd;
+        int compaction_index = 0;
+        char initial_nr_hugepages[10] = {0};
+        char nr_hugepages[10] = {0};
+
+        /* We want to test with 80% of available memory. Else, OOM killer comes
+           in to play */
+        mem_free = mem_free * 0.8;
+
+        fd = open("/proc/sys/vm/nr_hugepages", O_RDWR | O_NONBLOCK);
+        if (fd < 0) {
+                perror("Failed to open /proc/sys/vm/nr_hugepages");
+                return -1;
+        }
+
+        if (read(fd, initial_nr_hugepages, sizeof(initial_nr_hugepages)) <= 0) {
+                perror("Failed to read from /proc/sys/vm/nr_hugepages");
+                goto close_fd;
+        }
+
+        /* Start with the initial condition of 0 huge pages*/
+        if (write(fd, "0", sizeof(char)) != sizeof(char)) {
+                perror("Failed to write to /proc/sys/vm/nr_hugepages\n");
+                goto close_fd;
+        }
+
+        lseek(fd, 0, SEEK_SET);
+
+        /* Request a large number of huge pages. The Kernel will allocate
+           as much as it can */
+        if (write(fd, "100000", (6*sizeof(char))) != (6*sizeof(char))) {
+                perror("Failed to write to /proc/sys/vm/nr_hugepages\n");
+                goto close_fd;
+        }
+
+        lseek(fd, 0, SEEK_SET);
+
+        if (read(fd, nr_hugepages, sizeof(nr_hugepages)) <= 0) {
+                perror("Failed to read from /proc/sys/vm/nr_hugepages\n");
+                goto close_fd;
+        }
+
+        /* We should have been able to request at least 1/3 rd of the memory in
+           huge pages */
+        compaction_index = mem_free/(atoi(nr_hugepages) * hugepage_size);
+
+        if (compaction_index > 3) {
+                printf("No of huge pages allocated = %d\n",
+                       (atoi(nr_hugepages)));
+                fprintf(stderr, "ERROR: Less that 1/%d of memory is available\n"
+                        "as huge pages\n", compaction_index);
+                goto close_fd;
+        }
+
+        printf("No of huge pages allocated = %d\n",
+               (atoi(nr_hugepages)));
+
+        if (write(fd, initial_nr_hugepages, sizeof(initial_nr_hugepages))
+            != strlen(initial_nr_hugepages)) {
+                perror("Failed to write to /proc/sys/vm/nr_hugepages\n");
+                goto close_fd;
+        }
+
+        close(fd);
+        return 0;
+
+ close_fd:
+        close(fd);
+        printf("Not OK. Compaction test failed.");
+        return -1;
+}
+
+
+int main(int argc, char **argv)
+{
+        struct rlimit lim;
+        struct map_list *list, *entry;
+        size_t page_size, i;
+        void *map = NULL;
+        unsigned long mem_free = 0;
+        unsigned long hugepage_size = 0;
+        unsigned long mem_fragmentable = 0;
+
+        if (prereq() != 0) {
+                printf("Either the sysctl compact_unevictable_allowed is not\n"
+                       "set to 1 or couldn't read the proc file.\n"
+                       "Skipping the test\n");
+                return 0;
+        }
+
+        lim.rlim_cur = RLIM_INFINITY;
+        lim.rlim_max = RLIM_INFINITY;
+        if (setrlimit(RLIMIT_MEMLOCK, &lim)) {
+                perror("Failed to set rlimit:\n");
+                return -1;
+        }
+
+        page_size = getpagesize();
+
+        list = NULL;
+
+        if (read_memory_info(&mem_free, &hugepage_size) != 0) {
+                printf("ERROR: Cannot read meminfo\n");
+                return -1;
+        }
+
+        mem_fragmentable = mem_free * 0.8 / 1024;
+
+        while (mem_fragmentable > 0) {
+                map = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
+                           MAP_ANONYMOUS | MAP_PRIVATE | MAP_LOCKED, -1, 0);
+                if (map == MAP_FAILED)
+                        break;
+
+                entry = malloc(sizeof(struct map_list));
+                if (!entry) {
+                        munmap(map, MAP_SIZE);
+                        break;
+                }
+                entry->map = map;
+                entry->next = list;
+                list = entry;
+
+                /* Write something (in this case the address of the map) to
+                 * ensure that KSM can't merge the mapped pages
+                 */
+                for (i = 0; i < MAP_SIZE; i += page_size)
+                        *(unsigned long *)(map + i) = (unsigned long)map + i;
+
+                mem_fragmentable--;
+        }
+
+        for (entry = list; entry != NULL; entry = entry->next) {
+                munmap(entry->map, MAP_SIZE);
+                if (!entry->next)
+                        break;
+                entry = entry->next;
+        }
+
+        if (check_compaction(mem_free, hugepage_size) == 0)
+                return 0;
+
+        return -1;
+}
diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index c87b6812300d..49ece11ff7fd 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -90,4 +90,16 @@ fi
 umount $mnt
 rm -rf $mnt
 echo $nr_hugepgs > /proc/sys/vm/nr_hugepages
+
+echo "-----------------------"
+echo "running compaction_test"
+echo "-----------------------"
+./compaction_test
+if [ $? -ne 0 ]; then
+        echo "[FAIL]"
+        exitcode=1
+else
+        echo "[PASS]"
+fi
+
 exit $exitcode