From: Glauber Costa <glommer@redhat.com>
To: Zachary Amsden <zamsden@redhat.com>
Cc: kvm@vger.kernel.org, Avi Kivity <avi@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
John Stultz <johnstul@us.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [KVM timekeeping 12/35] Robust TSC compensation
Date: Fri, 20 Aug 2010 14:40:44 -0300 [thread overview]
Message-ID: <20100820174044.GG2937@mothafucka.localdomain> (raw)
In-Reply-To: <1282291669-25709-13-git-send-email-zamsden@redhat.com>
On Thu, Aug 19, 2010 at 10:07:26PM -1000, Zachary Amsden wrote:
> Make the match of TSC find TSC writes that are close to each other
> instead of perfectly identical; this allows the compensator to also
> work in migration / suspend scenarios.
>
> Signed-off-by: Zachary Amsden <zamsden@redhat.com>
> ---
> arch/x86/kvm/x86.c | 14 ++++++++++----
> 1 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 52680f6..0f3e5fb 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -928,21 +928,27 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
> struct kvm *kvm = vcpu->kvm;
> u64 offset, ns, elapsed;
> unsigned long flags;
> + s64 sdiff;
>
> spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
> offset = data - native_read_tsc();
> ns = get_kernel_ns();
> elapsed = ns - kvm->arch.last_tsc_nsec;
> + sdiff = data - kvm->arch.last_tsc_write;
> + if (sdiff < 0)
> + sdiff = -sdiff;
>
> /*
> - * Special case: identical write to TSC within 5 seconds of
> + * Special case: close write to TSC within 5 seconds of
> * another CPU is interpreted as an attempt to synchronize
> - * (the 5 seconds is to accomodate host load / swapping).
> + * The 5 seconds is to accomodate host load / swapping as
> + * well as any reset of TSC during the boot process.
> *
> * In that case, for a reliable TSC, we can match TSC offsets,
> - * or make a best guest using kernel_ns value.
> + * or make a best guest using elapsed value.
> */
> - if (data == kvm->arch.last_tsc_write && elapsed < 5ULL * NSEC_PER_SEC) {
> + if (sdiff < nsec_to_cycles(5ULL * NSEC_PER_SEC) &&
> + elapsed < 5ULL * NSEC_PER_SEC) {
> if (!check_tsc_unstable()) {
Isn't 5 way too long for this case?
next prev parent reply other threads:[~2010-08-20 17:40 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-20 8:07 KVM timekeeping and TSC virtualization Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 01/35] Drop vm_init_tsc Zachary Amsden
2010-08-20 16:54 ` Glauber Costa
2010-08-20 8:07 ` [KVM timekeeping 02/35] Convert TSC writes to TSC offset writes Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 03/35] Move TSC offset writes to common code Zachary Amsden
2010-08-20 17:06 ` Glauber Costa
2010-08-24 0:51 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 04/35] Fix SVM VMCB reset Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 05/35] Move TSC reset out of vmcb_init Zachary Amsden
2010-08-20 17:08 ` Glauber Costa
2010-08-24 0:52 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 06/35] TSC reset compensation Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 07/35] Make cpu_tsc_khz updates use local CPU Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 08/35] Warn about unstable TSC Zachary Amsden
2010-08-20 17:28 ` Glauber Costa
2010-08-24 0:56 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 09/35] Unify TSC logic Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 10/35] Fix deep C-state TSC desynchronization Zachary Amsden
2010-08-20 17:30 ` Glauber Costa
2010-09-14 9:10 ` Jan Kiszka
2010-09-14 9:27 ` Avi Kivity
2010-09-14 10:40 ` Jan Kiszka
2010-09-14 10:47 ` Avi Kivity
2010-09-14 19:32 ` Zachary Amsden
2010-09-14 22:26 ` Jan Kiszka
2010-09-14 23:40 ` Zachary Amsden
2010-09-15 5:34 ` Jan Kiszka
2010-09-15 7:55 ` Avi Kivity
2010-09-15 8:04 ` Jan Kiszka
2010-09-15 12:29 ` Glauber Costa
2010-09-15 4:07 ` Zachary Amsden
2010-09-15 8:09 ` Jan Kiszka
2010-09-15 12:32 ` Glauber Costa
2010-09-15 18:27 ` Jan Kiszka
2010-09-17 22:09 ` Zachary Amsden
2010-09-17 22:31 ` Zachary Amsden
2010-09-18 23:53 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 11/35] Add helper functions for time computation Zachary Amsden
2010-08-20 17:34 ` Glauber Costa
2010-08-24 0:58 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 12/35] Robust TSC compensation Zachary Amsden
2010-08-20 17:40 ` Glauber Costa [this message]
2010-08-24 1:01 ` Zachary Amsden
2010-08-24 21:33 ` Daniel Verkamp
2010-08-20 8:07 ` [KVM timekeeping 13/35] Perform hardware_enable in CPU_STARTING callback Zachary Amsden
2010-08-27 16:32 ` Jan Kiszka
2010-08-27 23:43 ` Zachary Amsden
2010-08-30 9:10 ` Jan Kiszka
2010-08-20 8:07 ` [KVM timekeeping 14/35] Add clock sync request to hardware enable Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 15/35] Move scale_delta into common header Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 16/35] Fix a possible backwards warp of kvmclock Zachary Amsden
2011-09-02 18:34 ` Philipp Hahn
2011-09-05 14:06 ` [BUG, PATCH-2.6.32] " Philipp Hahn
2011-09-12 11:32 ` Marcelo Tosatti
2010-08-20 8:07 ` [KVM timekeeping 17/35] Implement getnsboottime kernel API Zachary Amsden
2010-08-20 18:39 ` john stultz
2010-08-20 23:37 ` Zachary Amsden
2010-08-21 0:02 ` john stultz
2010-08-21 0:52 ` Zachary Amsden
2010-08-21 1:04 ` john stultz
2010-08-21 1:22 ` Zachary Amsden
2010-08-27 18:05 ` Jan Kiszka
2010-08-27 23:48 ` Zachary Amsden
2010-08-30 18:07 ` Jan Kiszka
2010-08-20 8:07 ` [KVM timekeeping 18/35] Use getnsboottime in KVM Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 19/35] Add timekeeping documentation Zachary Amsden
2010-08-20 17:50 ` Glauber Costa
2010-08-20 8:07 ` [KVM timekeeping 20/35] Make math work for other scales Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 21/35] Track max tsc_khz Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 22/35] Track tsc last write in vcpu Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 23/35] Set initial TSC rate conversion factors Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 24/35] Timer request function renaming Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 25/35] Add clock catchup mode Zachary Amsden
2010-08-25 17:27 ` Marcelo Tosatti
2010-08-25 20:48 ` Zachary Amsden
2010-08-25 22:01 ` Marcelo Tosatti
2010-08-25 23:38 ` Glauber Costa
2010-08-26 0:17 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 26/35] Catchup slower TSC to guest rate Zachary Amsden
2010-09-07 3:44 ` Dong, Eddie
2010-09-07 22:14 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 27/35] Add TSC trapping Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 28/35] Unstable TSC write compensation Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 29/35] TSC overrun protection Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 30/35] IOCTL for setting TSC rate Zachary Amsden
2010-08-20 17:56 ` Glauber Costa
2010-08-21 16:11 ` Arnd Bergmann
2010-08-20 8:07 ` [KVM timekeeping 31/35] Exit conditions for TSC trapping Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 32/35] Entry " Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 33/35] Indicate reliable TSC in kvmclock Zachary Amsden
2010-08-20 17:45 ` Glauber Costa
2010-08-24 1:14 ` Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 34/35] Remove dead code Zachary Amsden
2010-08-20 8:07 ` [KVM timekeeping 35/35] Add some debug stuff Zachary Amsden
2010-08-20 13:26 ` KVM timekeeping and TSC virtualization David S. Ahern
2010-08-20 23:24 ` Zachary Amsden
2010-08-22 1:32 ` David S. Ahern
2010-08-24 1:44 ` Zachary Amsden
2010-08-24 3:04 ` David S. Ahern
2010-08-24 5:47 ` Zachary Amsden
2010-08-24 13:32 ` David S. Ahern
2010-08-24 23:01 ` Zachary Amsden
2010-08-25 16:55 ` Marcelo Tosatti
2010-08-25 20:32 ` Zachary Amsden
2010-08-24 22:13 ` Marcelo Tosatti
2010-08-25 4:04 ` Zachary Amsden
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