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
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -756,3 +756,12 @@
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
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -80,6 +80,7 @@
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 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);