[PATCH v3 10/10] iov_iter: Add benchmarking kunit tests for UBUF/IOVEC

David Howells
2023-09-22T11:31:25Z

Add kunit tests to benchmark 256MiB copies to a UBUF iterator and an IOVEC
iterator. This attaches a userspace VM with a mapped file in it
temporarily to the test thread.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <brauner@kernel.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Matthew Wilcox <willy@infradead.org>
cc: David Hildenbrand <david@redhat.com>
cc: John Hubbard <jhubbard@nvidia.com>
cc: Brendan Higgins <brendanhiggins@google.com>
cc: David Gow <davidgow@google.com>
cc: linux-kselftest@vger.kernel.org
cc: kunit-dev@googlegroups.com
cc: linux-mm@kvack.org
cc: linux-fsdevel@vger.kernel.org
---
lib/kunit_iov_iter.c | 95 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 95 insertions(+)

diff --git a/lib/kunit_iov_iter.c b/lib/kunit_iov_iter.c
index 2fbe6f2afb26..d5b7517f4f47 100644
--- a/lib/kunit_iov_iter.c
+++ b/lib/kunit_iov_iter.c
@@ -1325,6 +1325,99 @@ static void *__init iov_kunit_create_source(struct kunit *test, size_t npages)
return scratch;
}

+/*
+ * Time copying 256MiB through an ITER_UBUF.
+ */
+static void __init iov_kunit_benchmark_ubuf(struct kunit *test)
+{
+ struct iov_iter iter;
+ unsigned int samples[IOV_KUNIT_NR_SAMPLES];
+ ktime_t a, b;
+ ssize_t copied;
+ size_t size = 256 * 1024 * 1024, npages = size / PAGE_SIZE;
+ void *scratch;
+ int i;
+ u8 __user *buffer;
+
+ /* Allocate a huge buffer and populate it with pages. */
+ buffer = iov_kunit_create_user_buf(test, npages, NULL);
+
+ /* Create a single large buffer to copy to/from. */
+ scratch = iov_kunit_create_source(test, npages);
+
+ /* Perform and time a bunch of copies. */
+ kunit_info(test, "Benchmarking copy_to_iter() over UBUF:\n");
+ for (i = 0; i < IOV_KUNIT_NR_SAMPLES; i++) {
+ size_t remain = size;
+
+ a = ktime_get_real();
+ do {
+ size_t part = min(remain, PAGE_SIZE);
+
+ iov_iter_ubuf(&iter, ITER_SOURCE, buffer, part);
+ copied = copy_from_iter(scratch, part, &iter);
+ KUNIT_EXPECT_EQ(test, copied, part);
+ remain -= part;
+ } while (remain > 0);
+ b = ktime_get_real();
+ samples[i] = ktime_to_us(ktime_sub(b, a));
+ }
+
+ iov_kunit_benchmark_print_stats(test, samples);
+ KUNIT_SUCCEED();
+}
+
+/*
+ * Time copying 256MiB through an ITER_IOVEC.
+ */
+static void __init iov_kunit_benchmark_iovec(struct kunit *test)
+{
+ struct iov_iter iter;
+ struct iovec *iov;
+ unsigned int samples[IOV_KUNIT_NR_SAMPLES];
+ ktime_t a, b;
+ ssize_t copied;
+ size_t size = 256 * 1024 * 1024, npages = size / PAGE_SIZE, part;
+ size_t ioc = size / PAGE_SIZE;
+ void *scratch;
+ int i;
+ u8 __user *buffer;
+
+ iov = kunit_kmalloc_array(test, ioc, sizeof(*iov), GFP_KERNEL);
+ KUNIT_ASSERT_NOT_NULL(test, iov);
+
+ /* Allocate a huge buffer and populate it with pages. */
+ buffer = iov_kunit_create_user_buf(test, npages, NULL);
+
+ /* Create a single large buffer to copy to/from. */
+ scratch = iov_kunit_create_source(test, npages);
+
+ /* Split the target over a number of iovecs */
+ copied = 0;
+ for (i = 0; i < ioc; i++) {
+ part = size / ioc;
+ iov[i].iov_base = buffer + copied;
+ iov[i].iov_len = part;
+ copied += part;
+ }
+ iov[i - 1].iov_len += size - part;
+
+ /* Perform and time a bunch of copies. */
+ kunit_info(test, "Benchmarking copy_to_iter() over IOVEC:\n");
+ for (i = 0; i < IOV_KUNIT_NR_SAMPLES; i++) {
+ iov_iter_init(&iter, ITER_SOURCE, iov, npages, size);
+
+ a = ktime_get_real();
+ copied = copy_from_iter(scratch, size, &iter);
+ b = ktime_get_real();
+ KUNIT_EXPECT_EQ(test, copied, size);
+ samples[i] = ktime_to_us(ktime_sub(b, a));
+ }
+
+ iov_kunit_benchmark_print_stats(test, samples);
+ KUNIT_SUCCEED();
+}
+
/*
* Time copying 256MiB through an ITER_KVEC.
*/
@@ -1611,6 +1704,8 @@ static struct kunit_case __refdata iov_kunit_cases[] = {
KUNIT_CASE(iov_kunit_extract_pages_kvec),
KUNIT_CASE(iov_kunit_extract_pages_bvec),
KUNIT_CASE(iov_kunit_extract_pages_xarray),
+ KUNIT_CASE(iov_kunit_benchmark_ubuf),
+ KUNIT_CASE(iov_kunit_benchmark_iovec),
KUNIT_CASE(iov_kunit_benchmark_kvec),
KUNIT_CASE(iov_kunit_benchmark_bvec),
KUNIT_CASE(iov_kunit_benchmark_bvec_split),