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If you try to enable NOHZ_FULL on a guest today, you'll get the following error when the guest tries to deactivate the scheduler tick: WARNING: CPU: 3 PID: 2182 at kernel/time/tick-sched.c:192 can_stop_full_tick+0xb9/0x290() NO_HZ FULL will not work with unstable sched clock CPU: 3 PID: 2182 Comm: kworker/3:1 Not tainted 4.0.0-10545-gb9bb6fb #204 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Workqueue: events flush_to_ldisc ffffffff8162a0c7 ffff88011f583e88 ffffffff814e6ba0 0000000000000002 ffff88011f583ed8 ffff88011f583ec8 ffffffff8104d095 ffff88011f583eb8 0000000000000000 0000000000000003 0000000000000001 0000000000000001 Call Trace: <IRQ> [<ffffffff814e6ba0>] dump_stack+0x4f/0x7b [<ffffffff8104d095>] warn_slowpath_common+0x85/0xc0 [<ffffffff8104d146>] warn_slowpath_fmt+0x46/0x50 [<ffffffff810bd2a9>] can_stop_full_tick+0xb9/0x290 [<ffffffff810bd9ed>] tick_nohz_irq_exit+0x8d/0xb0 [<ffffffff810511c5>] irq_exit+0xc5/0x130 [<ffffffff814f180a>] smp_apic_timer_interrupt+0x4a/0x60 [<ffffffff814eff5e>] apic_timer_interrupt+0x6e/0x80 <EOI> [<ffffffff814ee5d1>] ? _raw_spin_unlock_irqrestore+0x31/0x60 [<ffffffff8108bbc8>] __wake_up+0x48/0x60 [<ffffffff8134836c>] n_tty_receive_buf_common+0x49c/0xba0 [<ffffffff8134a6bf>] ? tty_ldisc_ref+0x1f/0x70 [<ffffffff81348a84>] n_tty_receive_buf2+0x14/0x20 [<ffffffff8134b390>] flush_to_ldisc+0xe0/0x120 [<ffffffff81064d05>] process_one_work+0x1d5/0x540 [<ffffffff81064c81>] ? process_one_work+0x151/0x540 [<ffffffff81065191>] worker_thread+0x121/0x470 [<ffffffff81065070>] ? process_one_work+0x540/0x540 [<ffffffff8106b4df>] kthread+0xef/0x110 [<ffffffff8106b3f0>] ? __kthread_parkme+0xa0/0xa0 [<ffffffff814ef4f2>] ret_from_fork+0x42/0x70 [<ffffffff8106b3f0>] ? __kthread_parkme+0xa0/0xa0 ---[ end trace 06e3507544a38866 ]--- However, it turns out that kvmclock does provide a stable sched_clock callback. So, let the scheduler know this which in turn makes NOHZ_FULL work in the guest. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| .. | ||
| boot | ||
| configs | ||
| crypto | ||
| ia32 | ||
| include | ||
| kernel | ||
| kvm | ||
| lguest | ||
| lib | ||
| math-emu | ||
| mm | ||
| net | ||
| oprofile | ||
| pci | ||
| platform | ||
| power | ||
| purgatory | ||
| realmode | ||
| syscalls | ||
| tools | ||
| um | ||
| vdso | ||
| video | ||
| xen | ||
| .gitignore | ||
| Kbuild | ||
| Kconfig | ||
| Kconfig.cpu | ||
| Kconfig.debug | ||
| Makefile | ||
| Makefile_32.cpu | ||
| Makefile.um | ||