Am 19.09.2011 17:02, schrieb Paolo Bonzini:
> On 09/19/2011 04:37 PM, Frediano Ziglio wrote:
>> Now that iothread is always compiled sending a signal seems only an
>> additional step. This patch also avoid writing to two pipe (one from signal
>> and one in qemu_service_io).
>>
>> Work with kvm enabled or disabled. strace output is more readable (less
>> syscalls).
>>
>> Signed-off-by: Frediano Ziglio<fredd...@gmail.com>
>> ---
>> cpus.c | 5 -----
>> posix-aio-compat.c | 29 +++++++++--------------------
>> 2 files changed, 9 insertions(+), 25 deletions(-)
>>
>> diff --git a/cpus.c b/cpus.c
>> index 54c188c..d0cfe91 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -380,11 +380,6 @@ static int qemu_signal_init(void)
>> int sigfd;
>> sigset_t set;
>>
>> - /* SIGUSR2 used by posix-aio-compat.c */
>> - sigemptyset(&set);
>> - sigaddset(&set, SIGUSR2);
>> - pthread_sigmask(SIG_UNBLOCK,&set, NULL);
>> -
>> /*
>> * SIG_IPI must be blocked in the main thread and must not be caught
>> * by sigwait() in the signal thread. Otherwise, the cpu thread will
>> diff --git a/posix-aio-compat.c b/posix-aio-compat.c
>> index 3193dbf..185d5b2 100644
>> --- a/posix-aio-compat.c
>> +++ b/posix-aio-compat.c
>> @@ -42,7 +42,6 @@ struct qemu_paiocb {
>> int aio_niov;
>> size_t aio_nbytes;
>> #define aio_ioctl_cmd aio_nbytes /* for QEMU_AIO_IOCTL */
>> - int ev_signo;
>> off_t aio_offset;
>>
>> QTAILQ_ENTRY(qemu_paiocb) node;
>> @@ -309,6 +308,8 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
>> return nbytes;
>> }
>>
>> +static void posix_aio_notify_event(void);
>> +
>> static void *aio_thread(void *unused)
>> {
>> pid_t pid;
>> @@ -381,7 +382,7 @@ static void *aio_thread(void *unused)
>> aiocb->ret = ret;
>> mutex_unlock(&lock);
>>
>> - if (kill(pid, aiocb->ev_signo)) die("kill failed");
>> + posix_aio_notify_event();
>> }
>>
>> cur_threads--;
>> @@ -548,18 +549,14 @@ static int posix_aio_flush(void *opaque)
>>
>> static PosixAioState *posix_aio_state;
>>
>> -static void aio_signal_handler(int signum)
>> +static void posix_aio_notify_event(void)
>> {
>> - if (posix_aio_state) {
>> - char byte = 0;
>> - ssize_t ret;
>> -
>> - ret = write(posix_aio_state->wfd,&byte, sizeof(byte));
>> - if (ret< 0&& errno != EAGAIN)
>> - die("write()");
>> - }
>> + char byte = 0;
>> + ssize_t ret;
>>
>> - qemu_service_io();
>> + ret = write(posix_aio_state->wfd,&byte, sizeof(byte));
>> + if (ret< 0&& errno != EAGAIN)
>> + die("write()");
>> }
>>
>> static void paio_remove(struct qemu_paiocb *acb)
>> @@ -623,7 +620,6 @@ BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int
>> fd,
>> return NULL;
>> acb->aio_type = type;
>> acb->aio_fildes = fd;
>> - acb->ev_signo = SIGUSR2;
>>
>> if (qiov) {
>> acb->aio_iov = qiov->iov;
>> @@ -651,7 +647,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int
>> fd,
>> return NULL;
>> acb->aio_type = QEMU_AIO_IOCTL;
>> acb->aio_fildes = fd;
>> - acb->ev_signo = SIGUSR2;
>> acb->aio_offset = 0;
>> acb->aio_ioctl_buf = buf;
>> acb->aio_ioctl_cmd = req;
>> @@ -665,7 +660,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int
>> fd,
>>
>> int paio_init(void)
>> {
>> - struct sigaction act;
>> PosixAioState *s;
>> int fds[2];
>> int ret;
>> @@ -675,11 +669,6 @@ int paio_init(void)
>>
>> s = g_malloc(sizeof(PosixAioState));
>>
>> - sigfillset(&act.sa_mask);
>> - act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
>> - act.sa_handler = aio_signal_handler;
>> - sigaction(SIGUSR2,&act, NULL);
>> -
>> s->first_aio = NULL;
>> if (qemu_pipe(fds) == -1) {
>> fprintf(stderr, "failed to create pipe\n");
>
> I think it is possible to go a step further, turn
> posix_aio_process_queue into a bottom half and get rid of the pipe
> altogether. This in turn would remove the only real user of
> io_process_queue in qemu_aio_set_fd_handler. However, this is already a
> nice improvement.
But without the fd, wouldn't the I/O thread possibly wait for much
longer until its select() times out and it starts processing BHs?
Kevin
