Extend memory caching of umove* functions

* ucopy.c (cached_raddr): Double the size.
(get_next_unused_idx, lookup_cached_raddr_idx, set_cached_raddr_idx):
New functions.
(vm_read_mem): Use them.  When the data to be fetched resides in
up to 4 adjacent memory pages, fetch these pages and cache them.
* tests/umovestr_cached_adjacent.c: New file.
* tests/pure_executables.list: Add umovestr_cached_adjacent.
* tests/.gitignore: Likewise.
* tests/umovestr_cached.test: Handle the first argument.
* tests/gen_tests.in (umovestr_cached_adjacent): New test.

1 files changed, 48 insertions, 0 deletions

diff --git a/tests/umovestr_cached_adjacent.c b/tests/umovestr_cached_adjacent.c
new file mode 100644
index 000000000..53a573b3d
--- /dev/null
+++ b/tests/umovestr_cached_adjacent.c
@@ -0,0 +1,48 @@
+/*
+ * Check effectiveness of umovestr memory caching.
+ *
+ * Copyright (c) 2019-2020 Dmitry V. Levin <ldv@altlinux.org>
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "tests.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/uio.h>
+
+int
+main(void)
+{
+	const size_t size = get_page_size() + (DEFAULT_STRLEN - 1);
+	char *const buf = tail_alloc(size);
+	fill_memory_ex(buf, DEFAULT_STRLEN * 2, 'a', 'z' - 'a' + 1);
+
+	struct iovec *const io = tail_alloc(sizeof(*io) * DEFAULT_STRLEN);
+	for (unsigned int i = 0; i < DEFAULT_STRLEN; ++i) {
+		io[i].iov_base = buf + i;
+		io[i].iov_len = DEFAULT_STRLEN;
+	}
+
+	tprintf("%s", "");
+
+	int rc = writev(-1, io, DEFAULT_STRLEN);
+	const char *errstr = sprintrc(rc);
+
+	tprintf("writev(-1, [");
+	for (unsigned int i = 0; i < DEFAULT_STRLEN; ++i) {
+		if (i)
+			tprintf(", ");
+		tprintf("{iov_base=\"%.*s\", iov_len=%u}",
+			(int) io[i].iov_len,
+			(char *) io[i].iov_base,
+			(unsigned int) io[i].iov_len);
+	}
+	tprintf("], %u) = %s\n", DEFAULT_STRLEN, errstr);
+
+	tprintf("+++ exited with 0 +++\n");
+	return 0;
+}