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qemu-e2k
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main: force enabling of I/O thread 

Enabling the I/O thread by default seems like an important part of declaring
1.0.  Besides allowing true SMP support with KVM, the I/O thread means that the
TCG VCPU doesn't have to multiplex itself with the I/O dispatch routines which
currently requires a (racey) signal based alarm system.

I know there have been concerns about performance.  I think so far the ones that
have come up (virtio-net) are most likely due to secondary reasons like
decreased batching.

I think we ought to force enabling I/O thread early in 1.0 development and
commit to resolving any lingering issues.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Anthony Liguori 2011-08-22 08:24:58 -05:00
parent d9cd446b4f
commit 12d4536f7d
6 changed files with 1 additions and 232 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
configure vendored
View File

@ -165,7 +165,6 @@ darwin_user="no"
bsd_user="no"
guest_base=""
uname_release=""
io_thread="no"
mixemu="no"
aix="no"
blobs="yes"
@ -723,8 +722,6 @@ for opt do
;;
--enable-attr) attr="yes"
;;
--enable-io-thread) io_thread="yes"
;;
--disable-blobs) blobs="no"
;;
--with-pkgversion=*) pkgversion=" ($optarg)"
@ -2158,12 +2155,6 @@ EOF
if compile_prog "" "" ; then
signalfd=yes
elif test "$kvm" = "yes" -a "$io_thread" != "yes"; then
echo
echo "ERROR: Host kernel lacks signalfd() support,"
echo "but KVM depends on it when the IO thread is disabled."
echo
exit 1
fi
# check if eventfd is supported
@ -2710,7 +2701,6 @@ echo "NPTL support $nptl"
echo "GUEST_BASE $guest_base"
echo "PIE user targets $user_pie"
echo "vde support $vde"
echo "IO thread $io_thread"
echo "Linux AIO support $linux_aio"
echo "ATTR/XATTR support $attr"
echo "Install blobs $blobs"
@ -2968,9 +2958,6 @@ if test "$xen" = "yes" ; then
echo "CONFIG_XEN_BACKEND=y" >> $config_host_mak
echo "CONFIG_XEN_CTRL_INTERFACE_VERSION=$xen_ctrl_version" >> $config_host_mak
fi
if test "$io_thread" = "yes" ; then
echo "CONFIG_IOTHREAD=y" >> $config_host_mak
fi
if test "$linux_aio" = "yes" ; then
echo "CONFIG_LINUX_AIO=y" >> $config_host_mak
fi

143
cpus.c
View File

@ -173,12 +173,9 @@ static void cpu_handle_guest_debug(CPUState *env)
{
gdb_set_stop_cpu(env);
qemu_system_debug_request();
#ifdef CONFIG_IOTHREAD
env->stopped = 1;
#endif
}
#ifdef CONFIG_IOTHREAD
static void cpu_signal(int sig)
{
if (cpu_single_env) {
@ -186,7 +183,6 @@ static void cpu_signal(int sig)
}
exit_request = 1;
}
#endif
#ifdef CONFIG_LINUX
static void sigbus_reraise(void)
@ -262,12 +258,6 @@ static void qemu_kvm_eat_signals(CPUState *env)
exit(1);
}
} while (sigismember(&chkset, SIG_IPI) || sigismember(&chkset, SIGBUS));
#ifndef CONFIG_IOTHREAD
if (sigismember(&chkset, SIGIO) || sigismember(&chkset, SIGALRM)) {
qemu_notify_event();
}
#endif
}
#else /* !CONFIG_LINUX */
@ -390,7 +380,6 @@ static int qemu_signal_init(void)
int sigfd;
sigset_t set;
#ifdef CONFIG_IOTHREAD
/* SIGUSR2 used by posix-aio-compat.c */
sigemptyset(&set);
sigaddset(&set, SIGUSR2);
@ -409,18 +398,6 @@ static int qemu_signal_init(void)
sigaddset(&set, SIGIO);
sigaddset(&set, SIGALRM);
sigaddset(&set, SIGBUS);
#else
sigemptyset(&set);
sigaddset(&set, SIGBUS);
if (kvm_enabled()) {
/*
* We need to process timer signals synchronously to avoid a race
* between exit_request check and KVM vcpu entry.
*/
sigaddset(&set, SIGIO);
sigaddset(&set, SIGALRM);
}
#endif
pthread_sigmask(SIG_BLOCK, &set, NULL);
sigfd = qemu_signalfd(&set);
@ -447,7 +424,6 @@ static void qemu_kvm_init_cpu_signals(CPUState *env)
sigact.sa_handler = dummy_signal;
sigaction(SIG_IPI, &sigact, NULL);
#ifdef CONFIG_IOTHREAD
pthread_sigmask(SIG_BLOCK, NULL, &set);
sigdelset(&set, SIG_IPI);
sigdelset(&set, SIGBUS);
@ -456,17 +432,7 @@ static void qemu_kvm_init_cpu_signals(CPUState *env)
fprintf(stderr, "kvm_set_signal_mask: %s\n", strerror(-r));
exit(1);
}
#else
sigemptyset(&set);
sigaddset(&set, SIG_IPI);
sigaddset(&set, SIGIO);
sigaddset(&set, SIGALRM);
pthread_sigmask(SIG_BLOCK, &set, NULL);
pthread_sigmask(SIG_BLOCK, NULL, &set);
sigdelset(&set, SIGIO);
sigdelset(&set, SIGALRM);
#endif
sigdelset(&set, SIG_IPI);
sigdelset(&set, SIGBUS);
r = kvm_set_signal_mask(env, &set);
@ -478,7 +444,6 @@ static void qemu_kvm_init_cpu_signals(CPUState *env)
static void qemu_tcg_init_cpu_signals(void)
{
#ifdef CONFIG_IOTHREAD
sigset_t set;
struct sigaction sigact;
@ -489,7 +454,6 @@ static void qemu_tcg_init_cpu_signals(void)
sigemptyset(&set);
sigaddset(&set, SIG_IPI);
pthread_sigmask(SIG_UNBLOCK, &set, NULL);
#endif
}
#else /* _WIN32 */
@ -535,106 +499,6 @@ static void qemu_tcg_init_cpu_signals(void)
}
#endif /* _WIN32 */
#ifndef CONFIG_IOTHREAD
int qemu_init_main_loop(void)
{
int ret;
ret = qemu_signal_init();
if (ret) {
return ret;
}
qemu_init_sigbus();
return qemu_event_init();
}
void qemu_main_loop_start(void)
{
}
void qemu_init_vcpu(void *_env)
{
CPUState *env = _env;
int r;
env->nr_cores = smp_cores;
env->nr_threads = smp_threads;
if (kvm_enabled()) {
r = kvm_init_vcpu(env);
if (r < 0) {
fprintf(stderr, "kvm_init_vcpu failed: %s\n", strerror(-r));
exit(1);
}
qemu_kvm_init_cpu_signals(env);
} else {
qemu_tcg_init_cpu_signals();
}
}
int qemu_cpu_is_self(void *env)
{
return 1;
}
void run_on_cpu(CPUState *env, void (*func)(void *data), void *data)
{
func(data);
}
void resume_all_vcpus(void)
{
}
void pause_all_vcpus(void)
{
}
void qemu_cpu_kick(void *env)
{
}
void qemu_cpu_kick_self(void)
{
#ifndef _WIN32
assert(cpu_single_env);
raise(SIG_IPI);
#else
abort();
#endif
}
void qemu_notify_event(void)
{
CPUState *env = cpu_single_env;
qemu_event_increment ();
if (env) {
cpu_exit(env);
}
if (next_cpu && env != next_cpu) {
cpu_exit(next_cpu);
}
exit_request = 1;
}
void qemu_mutex_lock_iothread(void) {}
void qemu_mutex_unlock_iothread(void) {}
void cpu_stop_current(void)
{
}
void vm_stop(int reason)
{
do_vm_stop(reason);
}
#else /* CONFIG_IOTHREAD */
QemuMutex qemu_global_mutex;
static QemuCond qemu_io_proceeded_cond;
static bool iothread_requesting_mutex;
@ -1028,8 +892,6 @@ void vm_stop(int reason)
do_vm_stop(reason);
}
#endif
static int tcg_cpu_exec(CPUState *env)
{
int ret;
@ -1084,11 +946,6 @@ bool cpu_exec_all(void)
qemu_clock_enable(vm_clock,
(env->singlestep_enabled & SSTEP_NOTIMER) == 0);
#ifndef CONFIG_IOTHREAD
if (qemu_alarm_pending()) {
break;
}
#endif
if (cpu_can_run(env)) {
if (kvm_enabled()) {
r = kvm_cpu_exec(env);

4
hw/qxl.c
View File

@ -1388,11 +1388,7 @@ static void init_pipe_signaling(PCIQXLDevice *d)
dprint(d, 1, "%s: pipe creation failed\n", __FUNCTION__);
return;
}
#ifdef CONFIG_IOTHREAD
fcntl(d->pipe[0], F_SETFL, O_NONBLOCK);
#else
fcntl(d->pipe[0], F_SETFL, O_NONBLOCK /* | O_ASYNC */);
#endif
fcntl(d->pipe[1], F_SETFL, O_NONBLOCK);
fcntl(d->pipe[0], F_SETOWN, getpid());

2
kvm-all.c
View File

@ -479,7 +479,7 @@ static int kvm_check_many_ioeventfds(void)
* Older kernels have a 6 device limit on the KVM io bus. Find out so we
* can avoid creating too many ioeventfds.
*/
#if defined(CONFIG_EVENTFD) && defined(CONFIG_IOTHREAD)
#if defined(CONFIG_EVENTFD)
int ioeventfds[7];
int i, ret = 0;
for (i = 0; i < ARRAY_SIZE(ioeventfds); i++) {

53
qemu-timer.c
View File

@ -101,22 +101,6 @@ static int64_t cpu_get_clock(void)
}
}
#ifndef CONFIG_IOTHREAD
static int64_t qemu_icount_delta(void)
{
if (!use_icount) {
return 5000 * (int64_t) 1000000;
} else if (use_icount == 1) {
/* When not using an adaptive execution frequency
we tend to get badly out of sync with real time,
so just delay for a reasonable amount of time. */
return 0;
} else {
return cpu_get_icount() - cpu_get_clock();
}
}
#endif
/* enable cpu_get_ticks() */
void cpu_enable_ticks(void)
{
@ -688,9 +672,7 @@ void configure_icount(const char *option)
if (!option)
return;
#ifdef CONFIG_IOTHREAD
vm_clock->warp_timer = qemu_new_timer_ns(rt_clock, icount_warp_rt, NULL);
#endif
if (strcmp(option, "auto") != 0) {
icount_time_shift = strtol(option, NULL, 0);
@ -1178,41 +1160,6 @@ void quit_timers(void)
int qemu_calculate_timeout(void)
{
#ifndef CONFIG_IOTHREAD
int timeout;
if (!vm_running)
timeout = 5000;
else {
/* XXX: use timeout computed from timers */
int64_t add;
int64_t delta;
/* Advance virtual time to the next event. */
delta = qemu_icount_delta();
if (delta > 0) {
/* If virtual time is ahead of real time then just
wait for IO. */
timeout = (delta + 999999) / 1000000;
} else {
/* Wait for either IO to occur or the next
timer event. */
add = qemu_next_icount_deadline();
/* We advance the timer before checking for IO.
Limit the amount we advance so that early IO
activity won't get the guest too far ahead. */
if (add > 10000000)
add = 10000000;
delta += add;
qemu_icount += qemu_icount_round (add);
timeout = delta / 1000000;
if (timeout < 0)
timeout = 0;
}
}
return timeout;
#else /* CONFIG_IOTHREAD */
return 1000;
#endif
}

18
vl.c
View File

@ -1445,17 +1445,6 @@ int main_loop_wait(int nonblocking)
return ret;
}
#ifndef CONFIG_IOTHREAD
static int vm_request_pending(void)
{
return powerdown_requested ||
reset_requested ||
shutdown_requested ||
debug_requested ||
vmstop_requested;
}
#endif
qemu_irq qemu_system_powerdown;
static void main_loop(void)
@ -1470,14 +1459,7 @@ static void main_loop(void)
qemu_main_loop_start();
for (;;) {
#ifdef CONFIG_IOTHREAD
nonblocking = !kvm_enabled() && last_io > 0;
#else
nonblocking = cpu_exec_all();
if (vm_request_pending()) {
nonblocking = true;
}
#endif
#ifdef CONFIG_PROFILER
ti = profile_getclock();
#endif