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>

diff --git a/mm/Kconfig b/mm/Kconfig
index 9c4bddd..03ff770 100644 (file)
--- 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 e7ebd17..e669f02 100644 (file)
--- 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 (file)
index 0000000..5c8e2ab
--- /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 e49eca1..7f45806 100644 (file)
--- 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 (file)
index 0000000..36df551
--- /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;
+}