On 29/04/2015 03:47, Marcelo Tosatti wrote: > On Thu, Apr 23, 2015 at 05:12:42PM -0400, Luiz Capitulino wrote: >> 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@xxxxxxxxxx> >> Signed-off-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx> >> --- >> >> PS: Original author of this patch is Marcelo. I did most of the >> testing and backported it to an older real-time kernel tree. Works >> like a charm. >> >> arch/x86/kernel/kvmclock.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c >> index 42caaef..4e03921 100644 >> --- a/arch/x86/kernel/kvmclock.c >> +++ b/arch/x86/kernel/kvmclock.c >> @@ -24,6 +24,7 @@ >> #include <linux/percpu.h> >> #include <linux/hardirq.h> >> #include <linux/memblock.h> >> +#include <linux/sched.h> >> >> #include <asm/x86_init.h> >> #include <asm/reboot.h> >> @@ -265,6 +266,8 @@ void __init kvmclock_init(void) >> >> if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) >> pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); >> + >> + set_sched_clock_stable(); >> } >> >> int __init kvm_setup_vsyscall_timeinfo(void) >> -- >> 1.9.3 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > Ping? 6 days, half of them during the merge window is not such a terrible roundtrip. Anyhow I've applied the patch and will probably push to kvm/queue today. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
