On 2011-08-22 15:24, Anthony Liguori wrote: > 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.
iothread enabled without [1] gives unacceptable performance for ARM emulation (Musicpal board) here. With that series applied, the host CPU load is measurably higher, but no longer excessively. As that series demonstrates, a major issue for TCG is that the iothread and the VCPU thread run in lock-step, almost nothing is parallelized. At least so far. Paolo and Peter (and to some degree /me) discussed some better TCG treading last Thursday. Jan [1] http://thread.gmane.org/gmane.comp.emulators.qemu/99658 > > 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 <aligu...@us.ibm.com> > --- > configure | 13 ----- > cpus.c | 143 > ---------------------------------------------------------- > hw/qxl.c | 4 -- > kvm-all.c | 2 +- > qemu-timer.c | 53 --------------------- > vl.c | 17 ------- > 6 files changed, 1 insertions(+), 231 deletions(-) > > diff --git a/configure b/configure > index 234a4c5..ef8d7ae 100755 > --- a/configure > +++ b/configure > @@ -165,7 +165,6 @@ darwin_user="no" > bsd_user="no" > guest_base="" > uname_release="" > -io_thread="no" > mixemu="no" > aix="no" > blobs="yes" > @@ -722,8 +721,6 @@ for opt do > ;; > --enable-attr) attr="yes" > ;; > - --enable-io-thread) io_thread="yes" > - ;; > --disable-blobs) blobs="no" > ;; > --with-pkgversion=*) pkgversion=" ($optarg)" > @@ -2159,12 +2156,6 @@ EOF > > if compile_prog "" "" ; then > signalfd=yes > -elif test "$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 > @@ -2711,7 +2702,6 @@ 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 $blobs" > @@ -2969,9 +2959,6 @@ if test "$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 > diff --git a/cpus.c b/cpus.c > index c996ac5..fe18a60 100644 > --- a/cpus.c > +++ b/cpus.c > @@ -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; > @@ -1036,8 +900,6 @@ void vm_stop(int reason) > do_vm_stop(reason); > } > > -#endif > - > static int tcg_cpu_exec(CPUState *env) > { > int ret; > @@ -1092,11 +954,6 @@ 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); > diff --git a/hw/qxl.c b/hw/qxl.c > index bab60a5..c3a3e97 100644 > --- a/hw/qxl.c > +++ b/hw/qxl.c > @@ -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()); > > diff --git a/kvm-all.c b/kvm-all.c > index 0ae2e26..fbb9ff3 100644 > --- a/kvm-all.c > +++ b/kvm-all.c > @@ -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++) { > diff --git a/qemu-timer.c b/qemu-timer.c > index 19313d3..46dd483 100644 > --- a/qemu-timer.c > +++ b/qemu-timer.c > @@ -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 > } > > diff --git a/vl.c b/vl.c > index d661e8e..11f5669 100644 > --- a/vl.c > +++ b/vl.c > @@ -1438,17 +1438,6 @@ void main_loop_wait(int nonblocking) > > } > > -#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) > @@ -1462,12 +1451,6 @@ static void main_loop(void) > qemu_main_loop_start(); > > for (;;) { > -#ifndef CONFIG_IOTHREAD > - nonblocking = cpu_exec_all(); > - if (vm_request_pending()) { > - nonblocking = true; > - } > -#endif > #ifdef CONFIG_PROFILER > ti = profile_getclock(); > #endif -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
