Hello Thomas, thanks for looking at this,
On 5/25/20 10:44 AM, Thomas Huth wrote: > On 22/05/2020 19.10, Claudio Fontana wrote: >> move the vcpu throttling functionality into its own module. >> >> This functionality is not specific to any accelerator, >> and it is used currently by migration to slow down guests to try to >> have migrations converge, and by the cocoa MacOS UI to throttle speed. >> >> cpu-throttle contains the controls to adjust and inspect throttle >> settings, start (set) and stop vcpu throttling, and the throttling >> function itself that is run periodically on vcpus to make them take a nap. >> >> Execution of the throttling function on all vcpus is triggered by a timer, >> registered at module initialization. >> >> No functionality change. > > Thanks for the update, sounds better now! > >> Signed-off-by: Claudio Fontana <cfont...@suse.de> >> --- >> MAINTAINERS | 1 + >> Makefile.target | 8 ++- >> cpu-throttle.c | 122 >> ++++++++++++++++++++++++++++++++++++++++++ >> cpus.c | 95 +++----------------------------- >> include/hw/core/cpu.h | 37 ------------- >> include/qemu/main-loop.h | 5 ++ >> include/sysemu/cpu-throttle.h | 50 +++++++++++++++++ >> migration/migration.c | 1 + >> migration/ram.c | 1 + >> 9 files changed, 195 insertions(+), 125 deletions(-) >> create mode 100644 cpu-throttle.c >> create mode 100644 include/sysemu/cpu-throttle.h >> >> diff --git a/MAINTAINERS b/MAINTAINERS >> index 3690f313c3..95be18c0b5 100644 >> --- a/MAINTAINERS >> +++ b/MAINTAINERS >> @@ -2148,6 +2148,7 @@ Main loop >> M: Paolo Bonzini <pbonz...@redhat.com> >> S: Maintained >> F: cpus.c >> +F: cpu-throttle.c >> F: include/qemu/main-loop.h >> F: include/sysemu/runstate.h >> F: util/main-loop.c >> diff --git a/Makefile.target b/Makefile.target >> index 8ed1eba95b..60cfa2a78b 100644 >> --- a/Makefile.target >> +++ b/Makefile.target >> @@ -152,7 +152,13 @@ endif #CONFIG_BSD_USER >> ######################################################### >> # System emulator target >> ifdef CONFIG_SOFTMMU >> -obj-y += arch_init.o cpus.o gdbstub.o balloon.o ioport.o >> +obj-y += arch_init.o >> +obj-y += cpus.o >> +obj-y += cpu-throttle.o > > Hmm, maybe the new files should rather be created in the softmmu/ folder > (now that we've got it)? And cpus.c could finally be moved there, too... > well, it's just an idea, I've got no strong opinion about this. Absolutely, yes. Initially I thought to do it in a later phase, but if the consensus is to start already to put stuff in place, I would be happy to do it. It would make things easier to understand, currently it is confusing to remember whether a component is user-mode only, softmmu, tcg-only, ... > >> +obj-y += gdbstub.o >> +obj-y += balloon.o >> +obj-y += ioport.o >> + >> obj-y += qtest.o >> obj-y += dump/ >> obj-y += hw/ >> diff --git a/cpu-throttle.c b/cpu-throttle.c >> new file mode 100644 >> index 0000000000..4e6b2818ca >> --- /dev/null >> +++ b/cpu-throttle.c >> @@ -0,0 +1,122 @@ >> +/* >> + * 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/osdep.h" >> +#include "qemu-common.h" >> +#include "qemu/thread.h" >> +#include "hw/core/cpu.h" >> +#include "qemu/main-loop.h" >> +#include "sysemu/cpus.h" >> +#include "sysemu/cpu-throttle.h" >> + >> +/* vcpu throttling controls */ >> +static QEMUTimer *throttle_timer; >> +static unsigned int throttle_percentage; >> + >> +#define CPU_THROTTLE_PCT_MIN 1 >> +#define CPU_THROTTLE_PCT_MAX 99 >> +#define CPU_THROTTLE_TIMESLICE_NS 10000000 >> + >> +static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque) >> +{ >> + double pct; >> + double throttle_ratio; >> + int64_t sleeptime_ns, endtime_ns; >> + >> + if (!cpu_throttle_get_percentage()) { >> + return; >> + } >> + >> + pct = (double)cpu_throttle_get_percentage() / 100; >> + throttle_ratio = pct / (1 - pct); >> + /* Add 1ns to fix double's rounding error (like 0.9999999...) */ >> + sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + >> 1); >> + endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns; >> + while (sleeptime_ns > 0 && !cpu->stop) { >> + if (sleeptime_ns > SCALE_MS) { >> + qemu_cond_timedwait_iothread(cpu->halt_cond, >> + sleeptime_ns / SCALE_MS); >> + } else { >> + qemu_mutex_unlock_iothread(); >> + g_usleep(sleeptime_ns / SCALE_US); >> + qemu_mutex_lock_iothread(); >> + } >> + sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME); >> + } >> + atomic_set(&cpu->throttle_thread_scheduled, 0); >> +} >> + >> +static void cpu_throttle_timer_tick(void *opaque) >> +{ >> + CPUState *cpu; >> + double pct; >> + >> + /* Stop the timer if needed */ >> + if (!cpu_throttle_get_percentage()) { >> + return; >> + } >> + CPU_FOREACH(cpu) { >> + if (!atomic_xchg(&cpu->throttle_thread_scheduled, 1)) { >> + async_run_on_cpu(cpu, cpu_throttle_thread, >> + RUN_ON_CPU_NULL); >> + } >> + } >> + >> + pct = (double)cpu_throttle_get_percentage() / 100; >> + timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) + >> + CPU_THROTTLE_TIMESLICE_NS / (1 - pct)); >> +} >> + >> +void cpu_throttle_set(int new_throttle_pct) >> +{ >> + /* Ensure throttle percentage is within valid range */ >> + new_throttle_pct = MIN(new_throttle_pct, CPU_THROTTLE_PCT_MAX); >> + new_throttle_pct = MAX(new_throttle_pct, CPU_THROTTLE_PCT_MIN); >> + >> + atomic_set(&throttle_percentage, new_throttle_pct); >> + >> + timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) + >> + CPU_THROTTLE_TIMESLICE_NS); >> +} >> + >> +void cpu_throttle_stop(void) >> +{ >> + atomic_set(&throttle_percentage, 0); >> +} >> + >> +bool cpu_throttle_active(void) >> +{ >> + return (cpu_throttle_get_percentage() != 0); >> +} >> + >> +int cpu_throttle_get_percentage(void) >> +{ >> + return atomic_read(&throttle_percentage); >> +} >> + >> +void cpu_throttle_init(void) >> +{ >> + throttle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL_RT, >> + cpu_throttle_timer_tick, NULL); >> +} >> diff --git a/cpus.c b/cpus.c >> index 5670c96bcf..3a46a4fc2b 100644 >> --- a/cpus.c >> +++ b/cpus.c > [...] >> >> +void qemu_cond_timedwait_iothread(QemuCond *cond, int ms) >> +{ >> + qemu_cond_timedwait(cond, &qemu_global_mutex, ms); >> +} > > So the new function is in cpus.c ... Yes, it is just below the very similar function it is derived from (the non-timed variant). > >> diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h >> index a6d20b0719..2fa3d90ad6 100644 >> --- a/include/qemu/main-loop.h >> +++ b/include/qemu/main-loop.h >> @@ -263,6 +263,11 @@ int qemu_add_child_watch(pid_t pid); >> */ >> bool qemu_mutex_iothread_locked(void); >> >> +/* >> + * qemu_cond_timedwait_iothread: like the previous, but with timeout >> + */ >> +void qemu_cond_timedwait_iothread(QemuCond *cond, int ms); > > ... but it's prototype is in main-loop.h ? That's a little bit > confusing... I'd rather expect it in include/sysemu/cpus.h instead? Or > should the new function rather be moved to softmmu/vl.c ? Here I tried to stay close to the existing code/convention for qemu_cond_wait_iothread, which together with other similar prototypes is in main_loop.h and implemented in cpus.c I agree that the current include files are not streamlined, but it would be surprising to find qemu_cond_wait_iothread and qemu_cond_timedwait_iothread in separate places. I noticed however that while the implementation is close to its sister function, I put the prototype in a non-obvious place, I think I should move it just below qemu_cond_wait_iothread. > > Thomas > Thanks! Claudio