Linux recently added a new io_uring(7) optimization API that QEMU
doesn't take advantage of yet. The liburing library that QEMU uses
has added a corresponding new API calling io_uring_register_ring_fd().
When this API is called after creating the ring, the io_uring_submit()
library function passes a flag to the io_uring_enter(2) syscall
allowing it to skip the ring file descriptor fdget()/fdput()
operations. This saves some CPU cycles.
Signed-off-by: Sam Li <faithilikerun@gmail.com>
Message-id:
20220531105011.111082-1-faithilikerun@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
#include "qapi/error.h"
#include "trace.h"
+
/* io_uring ring size */
#define MAX_ENTRIES 128
}
ioq_init(&s->io_q);
- return s;
+#ifdef CONFIG_LIBURING_REGISTER_RING_FD
+ if (io_uring_register_ring_fd(&s->ring) < 0) {
+ /*
+ * Only warn about this error: we will fallback to the non-optimized
+ * io_uring operations.
+ */
+ warn_report("failed to register linux io_uring ring file descriptor");
+ }
+#endif
+ return s;
}
void luring_cleanup(LuringState *s)
config_host_data.set('CONFIG_LIBSSH', libssh.found())
config_host_data.set('CONFIG_LINUX_AIO', libaio.found())
config_host_data.set('CONFIG_LINUX_IO_URING', linux_io_uring.found())
+config_host_data.set('CONFIG_LIBURING_REGISTER_RING_FD', cc.has_function('io_uring_register_ring_fd', prefix: '#include <liburing.h>', dependencies:linux_io_uring))
config_host_data.set('CONFIG_LIBPMEM', libpmem.found())
config_host_data.set('CONFIG_NUMA', numa.found())
config_host_data.set('CONFIG_OPENGL', opengl.found())