Replace posix-aio with custom thread pool

glibc implements posix-aio as a thread pool and imposes a number of limitations.

1) it limits one request per-file descriptor.  we hack around this by dup()'ing
file descriptors which is hideously ugly

2) it's impossible to add new interfaces and we need a vectored read/write
operation to properly support a zero-copy API.

What has been suggested to me by glibc folks, is to implement whatever new
interfaces we want and then it can eventually be proposed for standardization.
This requires that we implement our own posix-aio implementation though.

This patch implements posix-aio using pthreads.  It immediately eliminates the
need for fd pooling.

It performs at least as well as the current posix-aio code (in some
circumstances, even better).

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5996 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 56 insertions, 0 deletions

diff --git a/posix-aio-compat.h b/posix-aio-compat.h
new file mode 100644
index 0000000..5dddd71
--- /dev/null
+++ b/posix-aio-compat.h
@@ -0,0 +1,56 @@
+/*
+ * QEMU posix-aio emulation
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_POSIX_AIO_COMPAT_H
+#define QEMU_POSIX_AIO_COMPAT_H
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <signal.h>
+
+#include "sys-queue.h"
+
+#define QEMU_PAIO_CANCELED     0x01
+#define QEMU_PAIO_NOTCANCELED  0x02
+#define QEMU_PAIO_ALLDONE      0x03
+
+struct qemu_paiocb
+{
+    int aio_fildes;
+    void *aio_buf;
+    size_t aio_nbytes;
+    struct sigevent aio_sigevent;
+    off_t aio_offset;
+
+    /* private */
+    TAILQ_ENTRY(qemu_paiocb) node;
+    int is_write;
+    ssize_t ret;
+    int active;
+};
+
+struct qemu_paioinit
+{
+    unsigned int aio_threads;
+    unsigned int aio_num;
+    unsigned int aio_idle_time;
+};
+
+int qemu_paio_init(struct qemu_paioinit *aioinit);
+int qemu_paio_read(struct qemu_paiocb *aiocb);
+int qemu_paio_write(struct qemu_paiocb *aiocb);
+int qemu_paio_error(struct qemu_paiocb *aiocb);
+ssize_t qemu_paio_return(struct qemu_paiocb *aiocb);
+int qemu_paio_cancel(int fd, struct qemu_paiocb *aiocb);
+
+#endif