MDEV-36234: Add innodb_linux_aio

This controls which linux implementation to use for
innodb_use_native_aio=ON.

innodb_linux_aio=auto is equivalent to innodb_linux_aio=io_uring when
it is available, and falling back to innodb_linux_aio=aio when not.

Debian packaging is no longer aio exclusive or uring, so
for those older Debian or Ubuntu releases, its a remove_uring directive.
For more recent releases, add mandatory liburing for consistent packaging.

WITH_LIBAIO is now an independent option from WITH_URING.

is_linux_native_aio_supported(): Remove. This had originally been added in
mysql/mysql-server@0da310b69d in 2012
to fix an issue where io_submit() on CentOS 5.5 would return EINVAL
for a /tmp/#sql*.ibd file associated with CREATE TEMPORARY TABLE.
But, starting with commit 2e814d4702d71a04388386a9f591d14a35980bfe InnoDB
temporary tables will be written to innodb_temp_data_file_path.
The 2012 commit said that the error could occur on "old kernels".
Any GNU/Linux distribution that we currently support should be based
on a newer Linux kernel; for example, Red Hat Enterprise Linux 7
was released in 2014.

This is joint work with Daniel Black and Vladislav Vaintroub.

debian/autobake-deb.sh

@@ -64,11 +64,10 @@ add_lsb_base_depends()
   sed -e 's#lsof #lsb-base (>= 3.0-10),\n         lsof #' -i debian/control
 }
 
-replace_uring_with_aio()
+remove_uring()
 {
-  sed 's/liburing-dev/libaio-dev/g' -i debian/control
+  sed -e '/liburing-dev/d' -i debian/control
-  sed -e '/-DIGNORE_AIO_CHECK=ON/d' \
+  sed -e '/-DWITH_URING=ON/d' -i debian/rules
-      -e '/-DWITH_URING=ON/d' -i debian/rules
 }
 
 disable_libfmt()
@@ -116,7 +115,7 @@ in
   # Debian
   "buster")
     disable_libfmt
-    replace_uring_with_aio
+    remove_uring
     ;&
   "bullseye")
     add_lsb_base_depends
@@ -127,7 +126,7 @@ in
     # so no removal is necessary.
     if [[ ! "$architecture" =~ amd64|arm64|armel|armhf|i386|mips64el|mipsel|ppc64el|s390x ]]
     then
-      replace_uring_with_aio
+      remove_uring
     fi
     ;&
   "trixie"|"sid")
@@ -136,8 +135,8 @@ in
     ;;
   # Ubuntu
   "focal")
-    replace_uring_with_aio
     disable_libfmt
+    remove_uring
     ;&
   "jammy"|"kinetic")
     add_lsb_base_depends

debian/rules

@@ -87,9 +87,6 @@ endif
 	# quality standards in Debian. Also building it requires an extra 4 GB of disk
 	# space which makes native Debian builds fail as the total disk space needed
 	# for MariaDB becomes over 10 GB. Only build CS via autobake-deb.sh.
-	#
-	# Note: Don't use '-DWITH_URING=ON' as some Buildbot builders are missing it
-	# and would fail permanently.
 	PATH=$${MYSQL_BUILD_PATH:-"/usr/lib/ccache:/usr/local/bin:/usr/bin:/bin"} \
 	    dh_auto_configure --builddirectory=$(BUILDDIR) -- \
 	    -DCMAKE_BUILD_TYPE=RelWithDebInfo \
@@ -103,6 +100,8 @@ endif
 	    -DPLUGIN_AWS_KEY_MANAGEMENT=NO \
 	    -DPLUGIN_COLUMNSTORE=NO \
 	    -DIGNORE_AIO_CHECK=ON \
+	    -DWITH_URING=ON \
+	    -DWITH_LIBAIO=ON \
 	    -DDEB=$(DEB_VENDOR)
 
 # This is needed, otherwise 'make test' will run before binaries have been built

extra/mariabackup/xtrabackup.cc

@@ -378,6 +378,10 @@ extern const char *innodb_checksum_algorithm_names[];
 extern TYPELIB innodb_checksum_algorithm_typelib;
 extern const char *innodb_flush_method_names[];
 extern TYPELIB innodb_flush_method_typelib;
+#ifdef __linux__
+extern const char *innodb_linux_aio_names[];
+extern TYPELIB innodb_linux_aio_typelib;
+#endif
 
 static const char *binlog_info_values[] = {"off", "lockless", "on", "auto",
 					   NullS};
@@ -1334,6 +1338,9 @@ enum options_xtrabackup
   OPT_INNODB_READ_IO_THREADS,
   OPT_INNODB_WRITE_IO_THREADS,
   OPT_INNODB_USE_NATIVE_AIO,
+#ifdef __linux__
+  OPT_INNODB_LINUX_AIO,
+#endif
   OPT_INNODB_PAGE_SIZE,
   OPT_INNODB_BUFFER_POOL_FILENAME,
   OPT_INNODB_LOCK_WAIT_TIMEOUT,
@@ -1934,6 +1941,14 @@ struct my_option xb_server_options[] =
    (G_PTR*) &srv_use_native_aio,
    (G_PTR*) &srv_use_native_aio, 0, GET_BOOL, NO_ARG,
    TRUE, 0, 0, 0, 0, 0},
+#ifdef __linux__
+  {"innodb_linux_aio", OPT_INNODB_LINUX_AIO,
+   "Which linux AIO implementation to use, auto (io_uring, failing to aio) or explicit",
+   (G_PTR*) &srv_linux_aio_method,
+   (G_PTR*) &srv_linux_aio_method,
+   &innodb_linux_aio_typelib, GET_ENUM, REQUIRED_ARG,
+   SRV_LINUX_AIO_AUTO, 0, 0, 0, 0, 0},
+#endif
   {"innodb_page_size", OPT_INNODB_PAGE_SIZE,
    "The universal page size of the database.",
    (G_PTR*) &innobase_page_size, (G_PTR*) &innobase_page_size, 0,
@@ -2529,19 +2544,8 @@ static bool innodb_init_param()
 
 	ut_ad(DATA_MYSQL_BINARY_CHARSET_COLL == my_charset_bin.number);
 
-#ifdef _WIN32
+#if defined(_WIN32) || defined(LINUX_NATIVE_AIO) || defined(HAVE_URING)
 	srv_use_native_aio = TRUE;
-
-#elif defined(LINUX_NATIVE_AIO)
-
-	if (srv_use_native_aio) {
-		msg("InnoDB: Using Linux native AIO");
-	}
-#elif defined(HAVE_URING)
-
-	if (srv_use_native_aio) {
-		msg("InnoDB: Using liburing");
-	}
 #else
 	/* Currently native AIO is supported only on windows and linux
 	and that also when the support is compiled in. In all other
@@ -5473,7 +5477,6 @@ fail:
 	xb_fil_io_init();
 
 	if (os_aio_init()) {
-		msg("Error: cannot initialize AIO subsystem");
 		goto fail;
 	}
 

mysql-test/mariadb-test-run.pl

@@ -4548,7 +4548,7 @@ sub extract_warning_lines ($$) {
      qr|InnoDB: io_setup\(\) attempt|,
      qr|InnoDB: io_setup\(\) failed with EAGAIN|,
      qr|io_uring_queue_init\(\) failed with|,
-     qr|InnoDB: liburing disabled|,
+     qr|InnoDB: io_uring failed: falling back to libaio|,
      qr/InnoDB: Failed to set O_DIRECT on file/,
      qr|setrlimit could not change the size of core files to 'infinity';|,
      qr|failed to retrieve the MAC address|,

mysql-test/suite/sys_vars/r/innodb_linux_aio_basic.result

@@ -0,0 +1,21 @@
+select @@global.innodb_linux_aio;
+@@global.innodb_linux_aio
+auto
+select @@session.innodb_linux_aio;
+ERROR HY000: Variable 'innodb_linux_aio' is a GLOBAL variable
+show global variables like 'innodb_linux_aio';
+Variable_name	Value
+innodb_linux_aio	auto
+show session variables like 'innodb_linux_aio';
+Variable_name	Value
+innodb_linux_aio	auto
+select * from information_schema.global_variables where variable_name='innodb_linux_aio';
+VARIABLE_NAME	VARIABLE_VALUE
+INNODB_LINUX_AIO	auto
+select * from information_schema.session_variables where variable_name='innodb_linux_aio';
+VARIABLE_NAME	VARIABLE_VALUE
+INNODB_LINUX_AIO	auto
+set global innodb_linux_aio='auto';
+ERROR HY000: Variable 'innodb_linux_aio' is a read only variable
+set session innodb_linux_aio='aio';
+ERROR HY000: Variable 'innodb_linux_aio' is a read only variable

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -5,6 +5,7 @@ variable_name not in (
 'innodb_evict_tables_on_commit_debug', # one may want to override this
 'innodb_use_native_aio',            # default value depends on OS
 'innodb_log_file_buffering',        # only available on Linux and Windows
+'innodb_linux_aio',                 # existence depends on OS
 'innodb_buffer_pool_load_pages_abort')            # debug build only, and is only for testing
 order by variable_name;
 VARIABLE_NAME	INNODB_ADAPTIVE_FLUSHING

mysql-test/suite/sys_vars/t/innodb_linux_aio_basic.test

@@ -0,0 +1,23 @@
+--source include/have_innodb.inc
+--source include/linux.inc
+# enum readonly
+
+#
+# show values;
+#
+select @@global.innodb_linux_aio;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+select @@session.innodb_linux_aio;
+show global variables like 'innodb_linux_aio';
+show session variables like 'innodb_linux_aio';
+select * from information_schema.global_variables where variable_name='innodb_linux_aio';
+select * from information_schema.session_variables where variable_name='innodb_linux_aio';
+
+#
+# show that it's read-only
+#
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+set global innodb_linux_aio='auto';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+set session innodb_linux_aio='aio';
+

mysql-test/suite/sys_vars/t/sysvars_innodb.test

@@ -16,5 +16,6 @@ select VARIABLE_NAME, SESSION_VALUE, DEFAULT_VALUE, VARIABLE_SCOPE, VARIABLE_TYP
     'innodb_evict_tables_on_commit_debug', # one may want to override this
     'innodb_use_native_aio',            # default value depends on OS
     'innodb_log_file_buffering',        # only available on Linux and Windows
+    'innodb_linux_aio',                 # existence depends on OS
     'innodb_buffer_pool_load_pages_abort')            # debug build only, and is only for testing
   order by variable_name;

storage/innobase/handler/ha_innodb.cc

@@ -315,6 +315,25 @@ static TYPELIB innodb_stats_method_typelib = {
 	NULL
 };
 
+/** Possible values for system variable "innodb_linux_aio" */
+#ifdef __linux__
+const char* innodb_linux_aio_names[] = {
+	"auto",     /* SRV_LINUX_AIO_AUTO */
+	"io_uring", /* SRV_LINUX_AIO_IO_URING */
+	"aio",      /* SRV_LINUX_AIO_LIBAIO */
+	NullS
+};
+
+/** Used to define an enumerate type of the system variable
+innodb_linux_aio. Used by mariadb-backup too. */
+TYPELIB innodb_linux_aio_typelib = {
+	array_elements(innodb_linux_aio_names) - 1,
+	"innodb_linux_aio_typelib",
+	innodb_linux_aio_names,
+	NULL
+};
+#endif
+
 /** Possible values of the parameter innodb_checksum_algorithm */
 const char* innodb_checksum_algorithm_names[] = {
 	"crc32",
@@ -19664,6 +19683,15 @@ static MYSQL_SYSVAR_BOOL(use_native_aio, srv_use_native_aio,
   "Use native AIO if supported on this platform.",
   NULL, NULL, TRUE);
 
+#ifdef __linux__
+static MYSQL_SYSVAR_ENUM(linux_aio, srv_linux_aio_method,
+  PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
+  "Specifies which Linux AIO implementation should be used."
+  " Possible value are \"auto\" (default) to select io_uring"
+  " and fallback to aio, or explicit \"io_uring\" or \"aio\"",
+  nullptr, nullptr, SRV_LINUX_AIO_AUTO, &innodb_linux_aio_typelib);
+#endif
+
 #ifdef HAVE_LIBNUMA
 static MYSQL_SYSVAR_BOOL(numa_interleave, srv_numa_interleave,
   PLUGIN_VAR_NOCMDARG | PLUGIN_VAR_READONLY,
@@ -20059,6 +20087,9 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(tmpdir),
   MYSQL_SYSVAR(autoinc_lock_mode),
   MYSQL_SYSVAR(use_native_aio),
+#ifdef __linux__
+  MYSQL_SYSVAR(linux_aio),
+#endif
 #ifdef HAVE_LIBNUMA
   MYSQL_SYSVAR(numa_interleave),
 #endif /* HAVE_LIBNUMA */

storage/innobase/include/fil0fil.h

@@ -77,6 +77,19 @@ enum srv_flush_t
 #endif
 };
 
+/** Possible values of innodb_linux_aio */
+#ifdef __linux__
+enum srv_linux_aio_t
+{
+  /** auto, io_uring first and then aio */
+  SRV_LINUX_AIO_AUTO,
+  /** io_uring */
+  SRV_LINUX_AIO_IO_URING,
+  /** aio (libaio interface) */
+  SRV_LINUX_AIO_LIBAIO
+};
+#endif
+
 /** innodb_flush_method */
 extern ulong srv_file_flush_method;
 

storage/innobase/include/srv0srv.h

@@ -178,6 +178,12 @@ OS (provided we compiled Innobase with it in), otherwise we will
 use simulated aio.
 Currently we support native aio on windows and linux */
 extern my_bool	srv_use_native_aio;
+
+#ifdef __linux__
+/* This enum is defined which linux native io method to use */
+extern ulong	srv_linux_aio_method;
+#endif
+
 extern my_bool	srv_numa_interleave;
 
 /* Use atomic writes i.e disable doublewrite buffer */

storage/innobase/os/os0file.cc

@@ -52,10 +52,6 @@ Created 10/21/1995 Heikki Tuuri
 
 #include <tpool_structs.h>
 
-#ifdef LINUX_NATIVE_AIO
-#include <libaio.h>
-#endif /* LINUX_NATIVE_AIO */
-
 #ifdef HAVE_FALLOC_PUNCH_HOLE_AND_KEEP_SIZE
 # include <fcntl.h>
 # include <linux/falloc.h>
@@ -3084,132 +3080,6 @@ static void write_io_callback(void *c)
   write_slots->release(cb);
 }
 
-#ifdef LINUX_NATIVE_AIO
-/** Checks if the system supports native linux aio. On some kernel
-versions where native aio is supported it won't work on tmpfs. In such
-cases we can't use native aio.
-
-@return: true if supported, false otherwise. */
-static bool is_linux_native_aio_supported()
-{
-	File		fd;
-	io_context_t	io_ctx;
-	std::string log_file_path = get_log_file_path();
-
-	memset(&io_ctx, 0, sizeof(io_ctx));
-	if (io_setup(1, &io_ctx)) {
-
-		/* The platform does not support native aio. */
-
-		return(false);
-
-	}
-	else if (!srv_read_only_mode) {
-
-		/* Now check if tmpdir supports native aio ops. */
-		fd = mysql_tmpfile("ib");
-
-		if (fd < 0) {
-			ib::warn()
-				<< "Unable to create temp file to check"
-				" native AIO support.";
-
-			int ret = io_destroy(io_ctx);
-			ut_a(ret != -EINVAL);
-			ut_ad(ret != -EFAULT);
-
-			return(false);
-		}
-	}
-	else {
-		fd = my_open(log_file_path.c_str(), O_RDONLY | O_CLOEXEC,
-			     MYF(0));
-
-		if (fd == -1) {
-
-			ib::warn() << "Unable to open \"" << log_file_path
-				   << "\" to check native"
-				   << " AIO read support.";
-
-			int ret = io_destroy(io_ctx);
-			ut_a(ret != EINVAL);
-			ut_ad(ret != EFAULT);
-
-			return(false);
-		}
-	}
-
-	struct io_event	io_event;
-
-	memset(&io_event, 0x0, sizeof(io_event));
-
-	byte* ptr = static_cast<byte*>(aligned_malloc(srv_page_size,
-						      srv_page_size));
-
-	struct iocb	iocb;
-
-	/* Suppress valgrind warning. */
-	memset(ptr, 0, srv_page_size);
-	memset(&iocb, 0x0, sizeof(iocb));
-
-	struct iocb* p_iocb = &iocb;
-
-	if (!srv_read_only_mode) {
-
-		io_prep_pwrite(p_iocb, fd, ptr, srv_page_size, 0);
-
-	}
-	else {
-		ut_a(srv_page_size >= 512);
-		io_prep_pread(p_iocb, fd, ptr, 512, 0);
-	}
-
-	int	err = io_submit(io_ctx, 1, &p_iocb);
-
-	if (err >= 1) {
-		/* Now collect the submitted IO request. */
-		err = io_getevents(io_ctx, 1, 1, &io_event, NULL);
-	}
-
-	aligned_free(ptr);
-	my_close(fd, MYF(MY_WME));
-
-	switch (err) {
-	case 1:
-		{
-			int ret = io_destroy(io_ctx);
-			ut_a(ret != -EINVAL);
-			ut_ad(ret != -EFAULT);
-
-			return(true);
-		}
-
-	case -EINVAL:
-	case -ENOSYS:
-		ib::warn()
-			<< "Linux Native AIO not supported. You can either"
-			" move "
-			<< (srv_read_only_mode ? log_file_path : "tmpdir")
-			<< " to a file system that supports native"
-			" AIO or you can set innodb_use_native_aio to"
-			" FALSE to avoid this message.";
-
-		/* fall through. */
-	default:
-		ib::warn()
-			<< "Linux Native AIO check on "
-			<< (srv_read_only_mode ? log_file_path : "tmpdir")
-			<< "returned error[" << -err << "]";
-	}
-
-	int ret = io_destroy(io_ctx);
-	ut_a(ret != -EINVAL);
-	ut_ad(ret != -EFAULT);
-
-	return(false);
-}
-#endif
-
 int os_aio_init() noexcept
 {
   int max_write_events= int(srv_n_write_io_threads *
@@ -3217,41 +3087,56 @@ int os_aio_init() noexcept
   int max_read_events= int(srv_n_read_io_threads *
                            OS_AIO_N_PENDING_IOS_PER_THREAD);
   int max_events= max_read_events + max_write_events;
-  int ret;
+  int ret= 1;
-#if LINUX_NATIVE_AIO
-  if (srv_use_native_aio && !is_linux_native_aio_supported())
-    goto disable;
-#endif
 
-  ret= srv_thread_pool->configure_aio(srv_use_native_aio, max_events);
+#if defined __linux__ && (defined HAVE_URING || defined LINUX_NATIVE_AIO)
-
+  if (srv_use_native_aio)
-#ifdef LINUX_NATIVE_AIO
-  if (ret)
   {
-    ut_ad(srv_use_native_aio);
+    switch (srv_linux_aio_method) {
-disable:
+    case SRV_LINUX_AIO_AUTO:
-    ib::warn() << "Linux Native AIO disabled.";
+    case SRV_LINUX_AIO_IO_URING:
-    srv_use_native_aio= false;
-    ret= srv_thread_pool->configure_aio(false, max_events);
-  }
-#endif
-
 # ifdef HAVE_URING
+      ret= srv_thread_pool->configure_aio(srv_use_native_aio, max_events,
+                                          tpool::OS_IO_URING);
+# endif
+# ifdef LINUX_NATIVE_AIO
+#  ifdef HAVE_URING
+      if (ret && srv_linux_aio_method == SRV_LINUX_AIO_AUTO)
+        sql_print_warning("InnoDB: io_uring failed: falling back to libaio");
+      else
+        break;
+      /* fallthough */
+#  endif /* HAVE_URING */
+    case SRV_LINUX_AIO_LIBAIO:
+      ret= srv_thread_pool->configure_aio(srv_use_native_aio, max_events,
+                                          tpool::OS_AIO);
+# endif
+    }
     if (ret)
     {
-    ut_ad(srv_use_native_aio);
-    ib::warn()
-	    << "liburing disabled: falling back to innodb_use_native_aio=OFF";
       srv_use_native_aio= false;
-    ret= srv_thread_pool->configure_aio(false, max_events);
+      sql_print_warning("InnoDB: native AIO failed: falling back to"
+                        " innodb_use_native_aio=OFF");
     }
-#endif
+    else
+      sql_print_information("InnoDB: Using %s", srv_thread_pool
+                            ->get_aio_implementation());
+  }
+#endif /* linux */
+
+  if (ret)
+    ret= srv_thread_pool->configure_aio(srv_use_native_aio,
+                                        max_events,
+                                        tpool::OS_DEFAULT);
 
   if (!ret)
   {
     read_slots= new io_slots(max_read_events, srv_n_read_io_threads);
     write_slots= new io_slots(max_write_events, srv_n_write_io_threads);
   }
+  else
+    sql_print_error("InnoDB: Cannot initialize AIO sub-system");
+
   return ret;
 }
 
@@ -3290,8 +3175,8 @@ int os_aio_resize(ulint n_reader_threads, ulint n_writer_threads) noexcept
   int max_write_events= int(n_writer_threads * OS_AIO_N_PENDING_IOS_PER_THREAD);
   int events= max_read_events + max_write_events;
 
-  /** Do the Linux AIO dance (this will try to create a new
+  /* Do the Linux AIO dance (this will try to create a new
-  io context with changed max_events ,etc*/
+  io context with changed max_events, etc.) */
 
   int ret= srv_thread_pool->reconfigure_aio(srv_use_native_aio, events);
 

storage/innobase/srv/srv0srv.cc

@@ -137,6 +137,10 @@ OS (provided we compiled Innobase with it in), otherwise we will
 use simulated aio we build below with threads.
 Currently we support native aio on windows and linux */
 my_bool	srv_use_native_aio;
+#ifdef __linux__
+/* This enum is defined which linux native io method to use */
+ulong	srv_linux_aio_method;
+#endif
 my_bool	srv_numa_interleave;
 /** copy of innodb_use_atomic_writes; @see innodb_init_params() */
 my_bool	srv_use_atomic_writes;

storage/innobase/srv/srv0start.cc

@@ -1287,22 +1287,9 @@ dberr_t srv_start(bool create_new_db)
 	}
 
 	if (os_aio_init()) {
-		ib::error() << "Cannot initialize AIO sub-system";
-
 		return(srv_init_abort(DB_ERROR));
 	}
 
-#ifdef LINUX_NATIVE_AIO
-	if (srv_use_native_aio) {
-		ib::info() << "Using Linux native AIO";
-	}
-#endif
-#ifdef HAVE_URING
-	if (srv_use_native_aio) {
-		ib::info() << "Using liburing";
-	}
-#endif
-
 	fil_system.create(srv_file_per_table ? 50000 : 5000);
 
 	if (buf_pool.create()) {

tpool/CMakeLists.txt

@@ -3,16 +3,18 @@ IF(WIN32)
   SET(EXTRA_SOURCES tpool_win.cc aio_win.cc)
 ELSEIF(CMAKE_SYSTEM_NAME STREQUAL "Linux")
   OPTION(WITH_URING "Require that io_uring be used" OFF)
-  OPTION(WITH_LIBAIO "Require that libaio is used, unless uring is there" OFF)
+  OPTION(WITH_LIBAIO "Require that libaio is used" OFF)
   IF(WITH_URING)
     SET(URING_REQUIRED REQUIRED)
-  ELSEIF(WITH_LIBAIO)
+  ENDIF()
+  IF(WITH_LIBAIO)
     SET(LIBAIO_REQUIRED REQUIRED)
   ENDIF()
+  SET(EXTRA_SOURCES)
   FIND_PACKAGE(URING QUIET ${URING_REQUIRED})
   IF(URING_FOUND)
     SET(URING_FOUND ${URING_FOUND} PARENT_SCOPE)
-    SET(TPOOL_DEFINES "-DHAVE_URING" PARENT_SCOPE)
+    SET(TPOOL_DEFINES "-DHAVE_URING")
     ADD_DEFINITIONS(-DHAVE_URING)
     LINK_LIBRARIES(${URING_LIBRARIES})
     INCLUDE_DIRECTORIES(${URING_INCLUDE_DIRS})
@@ -27,16 +29,16 @@ ELSEIF(CMAKE_SYSTEM_NAME STREQUAL "Linux")
     IF(HAVE_IO_URING_MLOCK_SIZE)
       SET_SOURCE_FILES_PROPERTIES(aio_liburing.cc PROPERTIES COMPILE_FLAGS "-DHAVE_IO_URING_MLOCK_SIZE")
     ENDIF()
-  ELSE()
+  ENDIF()
   FIND_PACKAGE(LIBAIO QUIET ${LIBAIO_REQUIRED})
   IF(LIBAIO_FOUND)
-      SET(TPOOL_DEFINES "-DLINUX_NATIVE_AIO" PARENT_SCOPE)
+    SET(TPOOL_DEFINES ${TPOOL_DEFINES} "-DLINUX_NATIVE_AIO")
     ADD_DEFINITIONS(-DLINUX_NATIVE_AIO)
     INCLUDE_DIRECTORIES(${LIBAIO_INCLUDE_DIRS})
     LINK_LIBRARIES(${LIBAIO_LIBRARIES})
-      SET(EXTRA_SOURCES aio_linux.cc)
+    SET(EXTRA_SOURCES ${EXTRA_SOURCES} aio_linux.cc)
-    ENDIF()
   ENDIF()
+  SET(TPOOL_DEFINES ${TPOOL_DEFINES} PARENT_SCOPE)
 ENDIF()
 
 ADD_LIBRARY(tpool STATIC

tpool/aio_liburing.cc

@@ -79,8 +79,9 @@ public:
 
     thread_= std::thread(thread_routine, this);
   }
+  const char *get_implementation() const override { return "io_uring"; };
 
-  ~aio_uring() noexcept
+  ~aio_uring() noexcept override
   {
     {
       std::lock_guard<std::mutex> _(mutex_);
@@ -103,8 +104,8 @@ public:
 
   int submit_io(tpool::aiocb *cb) final
   {
-    cb->iov_base= cb->m_buffer;
+    cb->m_iovec.iov_base= cb->m_buffer;
-    cb->iov_len= cb->m_len;
+    cb->m_iovec.iov_len= cb->m_len;
 
     // The whole operation since io_uring_get_sqe() and till io_uring_submit()
     // must be atomical. This is because liburing provides thread-unsafe calls.
@@ -112,11 +113,9 @@ public:
 
     io_uring_sqe *sqe= io_uring_get_sqe(&uring_);
     if (cb->m_opcode == tpool::aio_opcode::AIO_PREAD)
-      io_uring_prep_readv(sqe, cb->m_fh, static_cast<struct iovec *>(cb), 1,
+      io_uring_prep_readv(sqe, cb->m_fh, &cb->m_iovec, 1, cb->m_offset);
-                          cb->m_offset);
     else
-      io_uring_prep_writev(sqe, cb->m_fh, static_cast<struct iovec *>(cb), 1,
+      io_uring_prep_writev(sqe, cb->m_fh, &cb->m_iovec, 1, cb->m_offset);
-                           cb->m_offset);
     io_uring_sqe_set_data(sqe, cb);
 
     return io_uring_submit(&uring_) == 1 ? 0 : -1;
@@ -203,11 +202,27 @@ private:
 namespace tpool
 {
 
-aio *create_linux_aio(thread_pool *pool, int max_aio)
+#ifdef LINUX_NATIVE_AIO
+aio *create_libaio(thread_pool* tp, int max_io);
+#endif
+
+aio *create_linux_aio(thread_pool *pool, int max_aio,
+                      aio_implementation implementation)
 {
+  switch (implementation) {
+  case OS_DEFAULT:
+  case OS_IO_URING:
     try {
       return new aio_uring(pool, max_aio);
-  } catch (std::runtime_error& error) {
+    } catch (std::runtime_error&) {
+      return nullptr;
+    }
+    break;
+#ifdef LINUX_NATIVE_AIO
+  case OS_AIO:
+    return create_libaio(pool, max_aio);
+#endif
+  default:
     return nullptr;
   }
 }

tpool/aio_linux.cc

@@ -13,13 +13,8 @@ You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111 - 1301 USA*/
 
-#include "tpool_structs.h"
 #include "tpool.h"
-
 #include <thread>
-# include <atomic>
-# include <cstdio>
-# include <libaio.h>
 #include <sys/syscall.h>
 
 /**
@@ -58,6 +53,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111 - 1301 USA*/
   will make this version of io_getevents return EINVAL.
 */
 static int my_getevents(io_context_t ctx, long min_nr, long nr, io_event *ev)
+  noexcept
 {
   int saved_errno= errno;
   int ret= syscall(__NR_io_getevents, reinterpret_cast<long>(ctx),
@@ -81,8 +77,9 @@ static int my_getevents(io_context_t ctx, long min_nr, long nr, io_event *ev)
   with io_getevents() and forward io completion callback to
   the worker threadpool.
 */
-namespace tpool
+namespace
 {
+using namespace tpool;
 
 class aio_linux final : public aio
 {
@@ -120,7 +117,7 @@ class aio_linux final : public aio
         for (int i= 0; i < ret; i++)
         {
           const io_event &event= events[i];
-          aiocb *iocb= static_cast<aiocb*>(event.obj);
+          aiocb *iocb= reinterpret_cast<aiocb*>(event.obj);
           if (static_cast<int>(event.res) < 0)
           {
             iocb->m_err= -event.res;
@@ -160,11 +157,10 @@ public:
 
   int submit_io(aiocb *cb) override
   {
-    io_prep_pread(static_cast<iocb*>(cb), cb->m_fh, cb->m_buffer, cb->m_len,
+    io_prep_pread(&cb->m_iocb, cb->m_fh, cb->m_buffer, cb->m_len, cb->m_offset);
-                  cb->m_offset);
     if (cb->m_opcode != aio_opcode::AIO_PREAD)
-      cb->aio_lio_opcode= IO_CMD_PWRITE;
+      cb->m_iocb.aio_lio_opcode= IO_CMD_PWRITE;
-    iocb *icb= static_cast<iocb*>(cb);
+    iocb *icb= &cb->m_iocb;
     int ret= io_submit(m_io_ctx, 1, &icb);
     if (ret == 1)
       return 0;
@@ -174,11 +170,20 @@ public:
 
   int bind(native_file_handle&) override { return 0; }
   int unbind(const native_file_handle&) override { return 0; }
+  const char *get_implementation() const override { return "Linux native AIO"; };
 };
 
 std::atomic<bool> aio_linux::shutdown_in_progress;
+}
 
-aio *create_linux_aio(thread_pool *pool, int max_io)
+namespace tpool
+{
+
+#ifdef HAVE_URING
+aio *create_libaio(thread_pool *pool, int max_io)
+#else
+aio *create_linux_aio(thread_pool *pool, int max_io, aio_implementation)
+#endif
 {
   io_context_t ctx;
   memset(&ctx, 0, sizeof ctx);
@@ -187,6 +192,7 @@ aio *create_linux_aio(thread_pool *pool, int max_io)
     fprintf(stderr, "io_setup(%d) returned %d\n", max_io, ret);
     return nullptr;
   }
+
   return new aio_linux(ctx, pool);
 }
 }

tpool/aio_simulated.cc

@@ -154,6 +154,7 @@ public:
 
   int bind(native_file_handle &fd) override { return 0; }
   int unbind(const native_file_handle &fd) override { return 0; }
+  const char *get_implementation() const override { return "simulated"; }
 };
 
 aio *create_simulated_aio(thread_pool *tp)

tpool/aio_win.cc

@@ -131,6 +131,7 @@ public:
       : GetLastError();
   }
   int unbind(const native_file_handle& fd) override { return 0; }
+  const char *get_implementation() const override { return "completion ports"; }
 };
 
 aio* create_win_aio(thread_pool* pool, int max_io)

tpool/tpool.h

@@ -128,12 +128,21 @@ constexpr size_t MAX_AIO_USERDATA_LEN= 4 * sizeof(void*);
 struct aiocb
 #ifdef _WIN32
   :OVERLAPPED
-#elif defined LINUX_NATIVE_AIO
-  :iocb
-#elif defined HAVE_URING
-  :iovec
 #endif
 {
+#if defined LINUX_NATIVE_AIO || defined HAVE_URING
+  union {
+# ifdef LINUX_NATIVE_AIO
+    /** The context between io_submit() and io_getevents();
+    must be the first data member! */
+    iocb m_iocb;
+# endif
+# ifdef HAVE_URING
+    /** The context between io_uring_submit() and io_uring_wait_cqe() */
+    iovec m_iovec;
+# endif
+  };
+#endif
   native_file_handle m_fh;
   aio_opcode m_opcode;
   unsigned long long m_offset;
@@ -173,6 +182,7 @@ public:
   virtual int bind(native_file_handle &fd)= 0;
   /** "Unind" file to AIO handler (used on Windows only) */
   virtual int unbind(const native_file_handle &fd)= 0;
+  virtual const char *get_implementation() const=0;
   virtual ~aio(){};
 protected:
   static void synchronous(aiocb *cb);
@@ -202,12 +212,21 @@ class thread_pool;
 
 extern aio *create_simulated_aio(thread_pool *tp);
 
+enum aio_implementation
+{
+  OS_DEFAULT
+#ifdef __linux__
+  , OS_IO_URING
+  , OS_AIO
+#endif
+};
+
 class thread_pool
 {
 protected:
   /* AIO handler */
-  std::unique_ptr<aio> m_aio;
+  std::unique_ptr<aio> m_aio{};
-  virtual aio *create_native_aio(int max_io)= 0;
+  virtual aio *create_native_aio(int max_io, aio_implementation)= 0;
 
 public:
   /**
@@ -217,10 +236,7 @@ public:
   void (*m_worker_init_callback)(void)= [] {};
   void (*m_worker_destroy_callback)(void)= [] {};
 
-  thread_pool()
+  thread_pool()= default;
-      : m_aio()
-  {
-  }
   virtual void submit_task(task *t)= 0;
   virtual timer* create_timer(callback_func func, void *data=nullptr) = 0;
   void set_thread_callbacks(void (*init)(), void (*destroy)())
@@ -230,10 +246,10 @@ public:
     m_worker_init_callback= init;
     m_worker_destroy_callback= destroy;
   }
-  int configure_aio(bool use_native_aio, int max_io)
+  int configure_aio(bool use_native_aio, int max_io, aio_implementation impl)
   {
     if (use_native_aio)
-      m_aio.reset(create_native_aio(max_io));
+      m_aio.reset(create_native_aio(max_io, impl));
     else
       m_aio.reset(create_simulated_aio(this));
     return !m_aio ? -1 : 0;
@@ -244,7 +260,12 @@ public:
     assert(m_aio);
     if (use_native_aio)
     {
-      auto new_aio = create_native_aio(max_io);
+      const aio_implementation impl=
+#ifdef LINUX_NATIVE_AIO
+        !strcmp(get_aio_implementation(), "Linux native AIO") ? OS_AIO :
+#endif
+        OS_DEFAULT;
+      auto new_aio= create_native_aio(max_io, impl);
       if (!new_aio)
         return -1;
       m_aio.reset(new_aio);
@@ -256,6 +277,10 @@ public:
   {
     m_aio.reset();
   }
+  const char *get_aio_implementation() const
+  {
+    return m_aio->get_implementation();
+  }
 
   /**
   Tweaks how fast worker threads are created, or how often they are signaled.

tpool/tpool_generic.cc

@@ -40,13 +40,13 @@ namespace tpool
 
 #ifdef __linux__
 # if defined(HAVE_URING) || defined(LINUX_NATIVE_AIO)
-  extern aio* create_linux_aio(thread_pool* tp, int max_io);
+  aio *create_linux_aio(thread_pool* tp, int max_io, aio_implementation);
 # else
-  aio *create_linux_aio(thread_pool *, int) { return nullptr; };
+  static aio *create_linux_aio(thread_pool *, int, aio_implementation)
+  { return nullptr; }
 # endif
-#endif
+#elif defined _WIN32
-#ifdef _WIN32
+  aio *create_win_aio(thread_pool* tp, int max_io);
-  extern aio* create_win_aio(thread_pool* tp, int max_io);
 #endif
 
   static const std::chrono::milliseconds LONG_TASK_DURATION = std::chrono::milliseconds(500);
@@ -299,16 +299,15 @@ public:
   void wait_begin() override;
   void wait_end() override;
   void submit_task(task *task) override;
-  aio *create_native_aio(int max_io) override
-  {
 #ifdef _WIN32
-    return create_win_aio(this, max_io);
+  aio *create_native_aio(int max_io, aio_implementation) override
-#elif defined(__linux__)
+  { return create_win_aio(this, max_io); }
-    return create_linux_aio(this,max_io);
+#elif defined __linux__
+  aio *create_native_aio(int max_io, aio_implementation impl) override
+  { return create_linux_aio(this, max_io, impl); }
 #else
-    return nullptr;
+  aio *create_native_aio(int, aio_implementation) override { return nullptr; }
 #endif
-  }
 
   class timer_generic : public thr_timer_t, public timer
   {

tpool/tpool_win.cc

@@ -206,6 +206,11 @@ class thread_pool_win : public thread_pool
         CloseThreadpoolIo(fd.m_ptp_io);
       return 0;
     }
+
+    /**
+     Expose implementation.
+    */
+    const char *get_implementation() const override { return "ThreadPool"; }
   };
 
   PTP_POOL m_ptp_pool;
@@ -268,7 +273,7 @@ public:
       abort();
   }
 
-  aio *create_native_aio(int max_io) override
+  aio *create_native_aio(int max_io, aio_implementation) override
   {
     return new native_aio(*this, max_io);
   }