qemu/main-loop.c
Michael Roth d34e8f6e9d main-loop: For tools, initialize timers as part of qemu_init_main_loop()
In some cases initializing the alarm timers can lead to non-negligable
overhead from programs that link against qemu-tool.o. At least,
setting a max-resolution WinMM alarm timer via mm_start_timer() (the
current default for Windows) can increase the "tick rate" on Windows
OSs and affect frequency scaling, and in the case of tools that run
in guest OSs such has qemu-ga, the impact can be fairly dramatic
(+20%/20% user/sys time on a core 2 processor was observed from an idle
Windows XP guest).

This patch doesn't address the issue directly (not sure what a good
solution would be for Windows, or what other situations it might be
noticeable), but it at least limits the scope of the issue to programs
that "opt-in" to using the main-loop.c functions by only enabling alarm
timers when qemu_init_main_loop() is called, which is already required
to make use of those facilities, so existing users shouldn't be
affected.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2012-02-01 14:45:02 -06:00

477 lines
12 KiB
C

/*
* QEMU System Emulator
*
* Copyright (c) 2003-2008 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu-common.h"
#include "qemu-timer.h"
#include "slirp/slirp.h"
#include "main-loop.h"
#ifndef _WIN32
#include "compatfd.h"
static int io_thread_fd = -1;
void qemu_notify_event(void)
{
/* Write 8 bytes to be compatible with eventfd. */
static const uint64_t val = 1;
ssize_t ret;
if (io_thread_fd == -1) {
return;
}
do {
ret = write(io_thread_fd, &val, sizeof(val));
} while (ret < 0 && errno == EINTR);
/* EAGAIN is fine, a read must be pending. */
if (ret < 0 && errno != EAGAIN) {
fprintf(stderr, "qemu_notify_event: write() failed: %s\n",
strerror(errno));
exit(1);
}
}
static void qemu_event_read(void *opaque)
{
int fd = (intptr_t)opaque;
ssize_t len;
char buffer[512];
/* Drain the notify pipe. For eventfd, only 8 bytes will be read. */
do {
len = read(fd, buffer, sizeof(buffer));
} while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
}
static int qemu_event_init(void)
{
int err;
int fds[2];
err = qemu_eventfd(fds);
if (err == -1) {
return -errno;
}
err = fcntl_setfl(fds[0], O_NONBLOCK);
if (err < 0) {
goto fail;
}
err = fcntl_setfl(fds[1], O_NONBLOCK);
if (err < 0) {
goto fail;
}
qemu_set_fd_handler2(fds[0], NULL, qemu_event_read, NULL,
(void *)(intptr_t)fds[0]);
io_thread_fd = fds[1];
return 0;
fail:
close(fds[0]);
close(fds[1]);
return err;
}
/* If we have signalfd, we mask out the signals we want to handle and then
* use signalfd to listen for them. We rely on whatever the current signal
* handler is to dispatch the signals when we receive them.
*/
static void sigfd_handler(void *opaque)
{
int fd = (intptr_t)opaque;
struct qemu_signalfd_siginfo info;
struct sigaction action;
ssize_t len;
while (1) {
do {
len = read(fd, &info, sizeof(info));
} while (len == -1 && errno == EINTR);
if (len == -1 && errno == EAGAIN) {
break;
}
if (len != sizeof(info)) {
printf("read from sigfd returned %zd: %m\n", len);
return;
}
sigaction(info.ssi_signo, NULL, &action);
if ((action.sa_flags & SA_SIGINFO) && action.sa_sigaction) {
action.sa_sigaction(info.ssi_signo,
(siginfo_t *)&info, NULL);
} else if (action.sa_handler) {
action.sa_handler(info.ssi_signo);
}
}
}
static int qemu_signal_init(void)
{
int sigfd;
sigset_t set;
/*
* 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
* not catch it reliably.
*/
sigemptyset(&set);
sigaddset(&set, SIG_IPI);
sigaddset(&set, SIGIO);
sigaddset(&set, SIGALRM);
sigaddset(&set, SIGBUS);
pthread_sigmask(SIG_BLOCK, &set, NULL);
sigdelset(&set, SIG_IPI);
sigfd = qemu_signalfd(&set);
if (sigfd == -1) {
fprintf(stderr, "failed to create signalfd\n");
return -errno;
}
fcntl_setfl(sigfd, O_NONBLOCK);
qemu_set_fd_handler2(sigfd, NULL, sigfd_handler, NULL,
(void *)(intptr_t)sigfd);
return 0;
}
#else /* _WIN32 */
HANDLE qemu_event_handle = NULL;
static void dummy_event_handler(void *opaque)
{
}
static int qemu_event_init(void)
{
qemu_event_handle = CreateEvent(NULL, FALSE, FALSE, NULL);
if (!qemu_event_handle) {
fprintf(stderr, "Failed CreateEvent: %ld\n", GetLastError());
return -1;
}
qemu_add_wait_object(qemu_event_handle, dummy_event_handler, NULL);
return 0;
}
void qemu_notify_event(void)
{
if (!qemu_event_handle) {
return;
}
if (!SetEvent(qemu_event_handle)) {
fprintf(stderr, "qemu_notify_event: SetEvent failed: %ld\n",
GetLastError());
exit(1);
}
}
static int qemu_signal_init(void)
{
return 0;
}
#endif
int main_loop_init(void)
{
int ret;
qemu_mutex_lock_iothread();
ret = qemu_signal_init();
if (ret) {
return ret;
}
/* Note eventfd must be drained before signalfd handlers run */
ret = qemu_event_init();
if (ret) {
return ret;
}
return 0;
}
static GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
static int n_poll_fds;
static int max_priority;
static void glib_select_fill(int *max_fd, fd_set *rfds, fd_set *wfds,
fd_set *xfds, struct timeval *tv)
{
GMainContext *context = g_main_context_default();
int i;
int timeout = 0, cur_timeout;
g_main_context_prepare(context, &max_priority);
n_poll_fds = g_main_context_query(context, max_priority, &timeout,
poll_fds, ARRAY_SIZE(poll_fds));
g_assert(n_poll_fds <= ARRAY_SIZE(poll_fds));
for (i = 0; i < n_poll_fds; i++) {
GPollFD *p = &poll_fds[i];
if ((p->events & G_IO_IN)) {
FD_SET(p->fd, rfds);
*max_fd = MAX(*max_fd, p->fd);
}
if ((p->events & G_IO_OUT)) {
FD_SET(p->fd, wfds);
*max_fd = MAX(*max_fd, p->fd);
}
if ((p->events & G_IO_ERR)) {
FD_SET(p->fd, xfds);
*max_fd = MAX(*max_fd, p->fd);
}
}
cur_timeout = (tv->tv_sec * 1000) + ((tv->tv_usec + 500) / 1000);
if (timeout >= 0 && timeout < cur_timeout) {
tv->tv_sec = timeout / 1000;
tv->tv_usec = (timeout % 1000) * 1000;
}
}
static void glib_select_poll(fd_set *rfds, fd_set *wfds, fd_set *xfds,
bool err)
{
GMainContext *context = g_main_context_default();
if (!err) {
int i;
for (i = 0; i < n_poll_fds; i++) {
GPollFD *p = &poll_fds[i];
if ((p->events & G_IO_IN) && FD_ISSET(p->fd, rfds)) {
p->revents |= G_IO_IN;
}
if ((p->events & G_IO_OUT) && FD_ISSET(p->fd, wfds)) {
p->revents |= G_IO_OUT;
}
if ((p->events & G_IO_ERR) && FD_ISSET(p->fd, xfds)) {
p->revents |= G_IO_ERR;
}
}
}
if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
g_main_context_dispatch(context);
}
}
#ifdef _WIN32
/***********************************************************/
/* Polling handling */
typedef struct PollingEntry {
PollingFunc *func;
void *opaque;
struct PollingEntry *next;
} PollingEntry;
static PollingEntry *first_polling_entry;
int qemu_add_polling_cb(PollingFunc *func, void *opaque)
{
PollingEntry **ppe, *pe;
pe = g_malloc0(sizeof(PollingEntry));
pe->func = func;
pe->opaque = opaque;
for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next);
*ppe = pe;
return 0;
}
void qemu_del_polling_cb(PollingFunc *func, void *opaque)
{
PollingEntry **ppe, *pe;
for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next) {
pe = *ppe;
if (pe->func == func && pe->opaque == opaque) {
*ppe = pe->next;
g_free(pe);
break;
}
}
}
/***********************************************************/
/* Wait objects support */
typedef struct WaitObjects {
int num;
HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
WaitObjectFunc *func[MAXIMUM_WAIT_OBJECTS + 1];
void *opaque[MAXIMUM_WAIT_OBJECTS + 1];
} WaitObjects;
static WaitObjects wait_objects = {0};
int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
{
WaitObjects *w = &wait_objects;
if (w->num >= MAXIMUM_WAIT_OBJECTS) {
return -1;
}
w->events[w->num] = handle;
w->func[w->num] = func;
w->opaque[w->num] = opaque;
w->num++;
return 0;
}
void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
{
int i, found;
WaitObjects *w = &wait_objects;
found = 0;
for (i = 0; i < w->num; i++) {
if (w->events[i] == handle) {
found = 1;
}
if (found) {
w->events[i] = w->events[i + 1];
w->func[i] = w->func[i + 1];
w->opaque[i] = w->opaque[i + 1];
}
}
if (found) {
w->num--;
}
}
static void os_host_main_loop_wait(int *timeout)
{
int ret, ret2, i;
PollingEntry *pe;
/* XXX: need to suppress polling by better using win32 events */
ret = 0;
for (pe = first_polling_entry; pe != NULL; pe = pe->next) {
ret |= pe->func(pe->opaque);
}
if (ret == 0) {
int err;
WaitObjects *w = &wait_objects;
qemu_mutex_unlock_iothread();
ret = WaitForMultipleObjects(w->num, w->events, FALSE, *timeout);
qemu_mutex_lock_iothread();
if (WAIT_OBJECT_0 + 0 <= ret && ret <= WAIT_OBJECT_0 + w->num - 1) {
if (w->func[ret - WAIT_OBJECT_0]) {
w->func[ret - WAIT_OBJECT_0](w->opaque[ret - WAIT_OBJECT_0]);
}
/* Check for additional signaled events */
for (i = (ret - WAIT_OBJECT_0 + 1); i < w->num; i++) {
/* Check if event is signaled */
ret2 = WaitForSingleObject(w->events[i], 0);
if (ret2 == WAIT_OBJECT_0) {
if (w->func[i]) {
w->func[i](w->opaque[i]);
}
} else if (ret2 != WAIT_TIMEOUT) {
err = GetLastError();
fprintf(stderr, "WaitForSingleObject error %d %d\n", i, err);
}
}
} else if (ret != WAIT_TIMEOUT) {
err = GetLastError();
fprintf(stderr, "WaitForMultipleObjects error %d %d\n", ret, err);
}
}
*timeout = 0;
}
#else
static inline void os_host_main_loop_wait(int *timeout)
{
}
#endif
int main_loop_wait(int nonblocking)
{
fd_set rfds, wfds, xfds;
int ret, nfds;
struct timeval tv;
int timeout;
if (nonblocking) {
timeout = 0;
} else {
timeout = qemu_calculate_timeout();
qemu_bh_update_timeout(&timeout);
}
os_host_main_loop_wait(&timeout);
tv.tv_sec = timeout / 1000;
tv.tv_usec = (timeout % 1000) * 1000;
/* poll any events */
/* XXX: separate device handlers from system ones */
nfds = -1;
FD_ZERO(&rfds);
FD_ZERO(&wfds);
FD_ZERO(&xfds);
#ifdef CONFIG_SLIRP
slirp_select_fill(&nfds, &rfds, &wfds, &xfds);
#endif
qemu_iohandler_fill(&nfds, &rfds, &wfds, &xfds);
glib_select_fill(&nfds, &rfds, &wfds, &xfds, &tv);
if (timeout > 0) {
qemu_mutex_unlock_iothread();
}
ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv);
if (timeout > 0) {
qemu_mutex_lock_iothread();
}
glib_select_poll(&rfds, &wfds, &xfds, (ret < 0));
qemu_iohandler_poll(&rfds, &wfds, &xfds, ret);
#ifdef CONFIG_SLIRP
slirp_select_poll(&rfds, &wfds, &xfds, (ret < 0));
#endif
qemu_run_all_timers();
/* Check bottom-halves last in case any of the earlier events triggered
them. */
qemu_bh_poll();
return ret;
}