Add a kunit test to benchmark an xarray containing 256MiB of data getting decanted into 256-page BVEC iterators that get copied from - modelling bufferage being drawn from the pagecache and batched up for I/O.
Signed-off-by: David Howells dhowells@redhat.com 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: 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-fsdevel@vger.kernel.org cc: linux-mm@kvack.org --- lib/kunit_iov_iter.c | 87 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+)
diff --git a/lib/kunit_iov_iter.c b/lib/kunit_iov_iter.c index 1a43e9518a63..2fbe6f2afb26 100644 --- a/lib/kunit_iov_iter.c +++ b/lib/kunit_iov_iter.c @@ -1509,6 +1509,92 @@ static void __init iov_kunit_benchmark_xarray(struct kunit *test) KUNIT_SUCCEED(); }
+/* + * Time copying 256MiB through an ITER_XARRAY, decanting it to ITER_BVECs. + */ +static void __init iov_kunit_benchmark_xarray_to_bvec(struct kunit *test) +{ + struct iov_iter xiter; + struct xarray *xarray; + struct page *page; + 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; + + /* Allocate a page and tile it repeatedly in the buffer. */ + page = alloc_page(GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, page); + kunit_add_action_or_reset(test, iov_kunit_free_page, page); + + xarray = iov_kunit_create_xarray(test); + + for (i = 0; i < npages; i++) { + void *x = xa_store(xarray, i, page, GFP_KERNEL); + + KUNIT_ASSERT_FALSE(test, xa_is_err(x)); + } + + /* 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 BVECs decanted from an XARRAY:\n"); + for (i = 0; i < IOV_KUNIT_NR_SAMPLES; i++) { + size = 256 * 1024 * 1024; + iov_iter_xarray(&xiter, ITER_SOURCE, xarray, 0, size); + a = ktime_get_real(); + + do { + struct iov_iter biter; + struct bio_vec *bvec; + struct page **pages; + size_t req, part, offset0, got; + int j; + + npages = 256; + req = min_t(size_t, size, npages * PAGE_SIZE); + bvec = kunit_kmalloc_array(test, npages, sizeof(bvec[0]), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, bvec); + + pages = (void *)bvec + array_size(npages, sizeof(bvec[0])) - + array_size(npages, sizeof(*pages)); + + part = iov_iter_extract_pages(&xiter, &pages, req, + npages, 0, &offset0); + KUNIT_EXPECT_NE(test, part, 0); + KUNIT_EXPECT_GT(test, part, 0); + + j = 0; + got = part; + do { + size_t chunk = min_t(size_t, got, PAGE_SIZE - offset0); + + bvec_set_page(&bvec[j++], page, chunk, offset0); + offset0 = 0; + got -= chunk; + } while (got > 0); + + iov_iter_bvec(&biter, ITER_SOURCE, bvec, j, part); + copied = copy_from_iter(scratch, part, &biter); + KUNIT_EXPECT_EQ(test, copied, part); + size -= copied; + if (test->status == KUNIT_FAILURE) + break; + } while (size > 0); + + b = ktime_get_real(); + samples[i] = ktime_to_us(ktime_sub(b, a)); + if (test->status == KUNIT_FAILURE) + break; + } + + iov_kunit_benchmark_print_stats(test, samples); + KUNIT_SUCCEED(); +} + static struct kunit_case __refdata iov_kunit_cases[] = { KUNIT_CASE(iov_kunit_copy_to_ubuf), KUNIT_CASE(iov_kunit_copy_from_ubuf), @@ -1529,6 +1615,7 @@ static struct kunit_case __refdata iov_kunit_cases[] = { KUNIT_CASE(iov_kunit_benchmark_bvec), KUNIT_CASE(iov_kunit_benchmark_bvec_split), KUNIT_CASE(iov_kunit_benchmark_xarray), + KUNIT_CASE(iov_kunit_benchmark_xarray_to_bvec), {} };