mm: add infrastructure for get_user_pages_fast() benchmarking

Performance of get_user_pages_fast() is critical for some workloads, but
it's tricky to test it directly.

This patch provides /sys/kernel/debug/gup_benchmark that helps with
testing performance of it.

See tools/testing/selftests/vm/gup_benchmark.c for userspace
counterpart.

Link: http://lkml.kernel.org/r/20170908215603.9189-2-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 92 insertions, 0 deletions

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index e49eca1915f8..7f45806bd863 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -18,6 +18,7 @@ TEST_GEN_FILES += transhuge-stress
 TEST_GEN_FILES += userfaultfd
 TEST_GEN_FILES += mlock-random-test
 TEST_GEN_FILES += virtual_address_range
+TEST_GEN_FILES += gup_benchmark
 
 TEST_PROGS := run_vmtests
 
diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c
new file mode 100644
index 000000000000..36df55132036
--- /dev/null
+++ b/tools/testing/selftests/vm/gup_benchmark.c
@@ -0,0 +1,91 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <linux/types.h>
+
+#define MB (1UL << 20)
+#define PAGE_SIZE sysconf(_SC_PAGESIZE)
+
+#define GUP_FAST_BENCHMARK      _IOWR('g', 1, struct gup_benchmark)
+
+struct gup_benchmark {
+        __u64 delta_usec;
+        __u64 addr;
+        __u64 size;
+        __u32 nr_pages_per_call;
+        __u32 flags;
+};
+
+int main(int argc, char **argv)
+{
+        struct gup_benchmark gup;
+        unsigned long size = 128 * MB;
+        int i, fd, opt, nr_pages = 1, thp = -1, repeats = 1, write = 0;
+        char *p;
+
+        while ((opt = getopt(argc, argv, "m:r:n:tT")) != -1) {
+                switch (opt) {
+                case 'm':
+                        size = atoi(optarg) * MB;
+                        break;
+                case 'r':
+                        repeats = atoi(optarg);
+                        break;
+                case 'n':
+                        nr_pages = atoi(optarg);
+                        break;
+                case 't':
+                        thp = 1;
+                        break;
+                case 'T':
+                        thp = 0;
+                        break;
+                case 'w':
+                        write = 1;
+                default:
+                        return -1;
+                }
+        }
+
+        gup.nr_pages_per_call = nr_pages;
+        gup.flags = write;
+
+        fd = open("/sys/kernel/debug/gup_benchmark", O_RDWR);
+        if (fd == -1)
+                perror("open"), exit(1);
+
+        p = mmap(NULL, size, PROT_READ | PROT_WRITE,
+                        MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+        if (p == MAP_FAILED)
+                perror("mmap"), exit(1);
+        gup.addr = (unsigned long)p;
+
+        if (thp == 1)
+                madvise(p, size, MADV_HUGEPAGE);
+        else if (thp == 0)
+                madvise(p, size, MADV_NOHUGEPAGE);
+
+        for (; (unsigned long)p < gup.addr + size; p += PAGE_SIZE)
+                p[0] = 0;
+
+        for (i = 0; i < repeats; i++) {
+                gup.size = size;
+                if (ioctl(fd, GUP_FAST_BENCHMARK, &gup))
+                        perror("ioctl"), exit(1);
+
+                printf("Time: %lld us", gup.delta_usec);
+                if (gup.size != size)
+                        printf(", truncated (size: %lld)", gup.size);
+                printf("\n");
+        }
+
+        return 0;
+}