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>

5 files changed, 202 insertions, 0 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 9c4bdddd80c2..03ff7703d322 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -756,3 +756,12 @@ config PERCPU_STATS
           This feature collects and exposes statistics via debugfs. The
           information includes global and per chunk statistics, which can
           be used to help understand percpu memory usage.
+
+config GUP_BENCHMARK
+        bool "Enable infrastructure for get_user_pages_fast() benchmarking"
+        default n
+        help
+          Provides /sys/kernel/debug/gup_benchmark that helps with testing
+          performance of get_user_pages_fast().
+
+          See tools/testing/selftests/vm/gup_benchmark.c
diff --git a/mm/Makefile b/mm/Makefile
index e7ebd176fb93..e669f02c5a54 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -80,6 +80,7 @@ obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
 obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
 obj-$(CONFIG_MEMCG_SWAP) += swap_cgroup.o
 obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
+obj-$(CONFIG_GUP_BENCHMARK) += gup_benchmark.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
 obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
 obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
new file mode 100644
index 000000000000..5c8e2abeaa15
--- /dev/null
+++ b/mm/gup_benchmark.c
@@ -0,0 +1,100 @@
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/ktime.h>
+#include <linux/debugfs.h>
+
+#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;
+};
+
+static int __gup_benchmark_ioctl(unsigned int cmd,
+                struct gup_benchmark *gup)
+{
+        ktime_t start_time, end_time;
+        unsigned long i, nr, nr_pages, addr, next;
+        struct page **pages;
+
+        nr_pages = gup->size / PAGE_SIZE;
+        pages = kvmalloc(sizeof(void *) * nr_pages, GFP_KERNEL);
+        if (!pages)
+                return -ENOMEM;
+
+        i = 0;
+        nr = gup->nr_pages_per_call;
+        start_time = ktime_get();
+        for (addr = gup->addr; addr < gup->addr + gup->size; addr = next) {
+                if (nr != gup->nr_pages_per_call)
+                        break;
+
+                next = addr + nr * PAGE_SIZE;
+                if (next > gup->addr + gup->size) {
+                        next = gup->addr + gup->size;
+                        nr = (next - addr) / PAGE_SIZE;
+                }
+
+                nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
+                i += nr;
+        }
+        end_time = ktime_get();
+
+        gup->delta_usec = ktime_us_delta(end_time, start_time);
+        gup->size = addr - gup->addr;
+
+        for (i = 0; i < nr_pages; i++) {
+                if (!pages[i])
+                        break;
+                put_page(pages[i]);
+        }
+
+        kvfree(pages);
+        return 0;
+}
+
+static long gup_benchmark_ioctl(struct file *filep, unsigned int cmd,
+                unsigned long arg)
+{
+        struct gup_benchmark gup;
+        int ret;
+
+        if (cmd != GUP_FAST_BENCHMARK)
+                return -EINVAL;
+
+        if (copy_from_user(&gup, (void __user *)arg, sizeof(gup)))
+                return -EFAULT;
+
+        ret = __gup_benchmark_ioctl(cmd, &gup);
+        if (ret)
+                return ret;
+
+        if (copy_to_user((void __user *)arg, &gup, sizeof(gup)))
+                return -EFAULT;
+
+        return 0;
+}
+
+static const struct file_operations gup_benchmark_fops = {
+        .open = nonseekable_open,
+        .unlocked_ioctl = gup_benchmark_ioctl,
+};
+
+static int gup_benchmark_init(void)
+{
+        void *ret;
+
+        ret = debugfs_create_file_unsafe("gup_benchmark", 0600, NULL, NULL,
+                        &gup_benchmark_fops);
+        if (!ret)
+                pr_warn("Failed to create gup_benchmark in debugfs");
+
+        return 0;
+}
+
+late_initcall(gup_benchmark_init);
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);
+