From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, "Liran Alon" <liran.alon@oracle.com>,
"Wanpeng Li" <wanpengli@tencent.com>
Subject: Re: [PATCH v3 4/9] KVM: lapic: Allow user to disable auto-tuning of timer advancement
Date: Wed, 17 Apr 2019 08:22:03 -0700 [thread overview]
Message-ID: <20190417152203.GC8567@linux.intel.com> (raw)
In-Reply-To: <771a1410-e290-b017-1c54-3abbe069d4a2@redhat.com>
On Wed, Apr 17, 2019 at 02:59:43PM +0200, Paolo Bonzini wrote:
> On 16/04/19 22:32, Sean Christopherson wrote:
> > +static bool __read_mostly lapic_timer_advance_autotune = true;
> > +module_param(lapic_timer_advance_autotune, bool, S_IRUGO | S_IWUSR);
> > +
>
> Could we just have lapic_timer_advance_ns = 0 mean "adaptive tuning,
> starting from a default of 1000" and anything else mean "no tuning, just
> use this value"?
Originally I implemented a variation of that, except I disabled autotuning
if lapic_timer_advance_ns was set to anything other than the default.
Liran requested a separate param since the behavior was admittedly a bit
sneaky, and I didn't have a strong opinion either way, so here we are.
I think 'lapic_timer_advance_ns = 0' should be used to disable the
advancement. What if we make the param a signed int and have '-1' select
the "adaptive tuning ..." option? That could also be the default. It
saves a param and is hopefully more intuitive than what I originally
proposed.
next prev parent reply other threads:[~2019-04-17 15:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 20:32 [PATCH v3 0/9] KVM: lapic: Fix a variety of timer adv issues Sean Christopherson
2019-04-16 20:32 ` [PATCH v3 1/9] KVM: lapic: Hard cap the auto-calculated timer advancement Sean Christopherson
2019-04-17 12:57 ` Paolo Bonzini
2019-04-17 14:34 ` Sean Christopherson
2019-04-17 15:00 ` Paolo Bonzini
2019-04-16 20:32 ` [PATCH v3 2/9] KVM: lapic: Convert guest TSC to host time domain when delaying Sean Christopherson
2019-04-17 12:56 ` Paolo Bonzini
2019-04-17 14:33 ` Sean Christopherson
2019-04-17 15:05 ` Paolo Bonzini
2019-04-16 20:32 ` [PATCH v3 3/9] KVM: lapic: Track lapic timer advance per vCPU Sean Christopherson
2019-04-16 20:32 ` [PATCH v3 4/9] KVM: lapic: Allow user to disable auto-tuning of timer advancement Sean Christopherson
2019-04-17 12:59 ` Paolo Bonzini
2019-04-17 15:22 ` Sean Christopherson [this message]
2019-04-16 20:32 ` [PATCH v3 5/9] KVM: lapic: Busy wait for timer to expire when using hv_timer Sean Christopherson
2019-04-16 20:32 ` [PATCH v3 6/9] KVM: lapic: Explicitly cancel the hv timer if it's pre-expired Sean Christopherson
2019-04-16 20:32 ` [PATCH v3 7/9] KVM: lapic: Refactor ->set_hv_timer to use an explicit expired param Sean Christopherson
2019-04-17 13:02 ` Paolo Bonzini
2019-04-16 20:32 ` [PATCH v3 8/9] KVM: lapic: Check for a pending timer intr prior to start_hv_timer() Sean Christopherson
2019-04-16 20:32 ` [PATCH v3 9/9] KVM: VMX: Skip delta_tsc shift-and-divide if the dividend is zero Sean Christopherson
2019-04-17 13:06 ` [PATCH v3 0/9] KVM: lapic: Fix a variety of timer adv issues Paolo Bonzini
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