From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Gleb Natapov <gleb@kernel.org>,
Raghavendra KT <raghavendra.kt@linux.vnet.ibm.com>,
Vinod Chegu <chegu_vinod@hp.com>, Hui-Zhi <hui-zhi.zhao@hp.com>
Subject: Re: [PATCH 9/9] KVM: VMX: automatic PLE window maximum
Date: Wed, 20 Aug 2014 14:41:12 +0200 [thread overview]
Message-ID: <20140820124112.GC28873@potion.brq.redhat.com> (raw)
In-Reply-To: <53F44B40.6060806@redhat.com>
2014-08-20 09:16+0200, Paolo Bonzini:
> Il 19/08/2014 22:35, Radim Krčmář ha scritto:
> > Every increase of ple_window_grow creates potential overflows.
> > They are not serious, because we clamp ple_window and userspace is
> > expected to fix ple_window_max within a second.
> > ---
> I think avoiding overflows is better. In fact, I think you should call
> this function for ple_window_max too.
(Ack, I just wanted to avoid the worst userspace error, which is why
PW_max hasn't changed when PW_grow got smaller and we could overflow.)
> You could keep the ple_window_max variable to the user-set value.
> Whenever ple_window_grow or ple_window_max are changed, you can set an
> internal variable (let's call it ple_window_actual_max, but I'm not wed
> to this name) to the computed value, and then do:
>
> if (ple_window_grow < 1 || ple_window_actual_max < ple_window)
> new = ple_window;
> else if (ple_window_grow < ple_window)
> new = max(ple_window_actual_max, old) * ple_window_grow;
> else
> new = max(ple_window_actual_max, old) + ple_window_grow;
Oh, I like that this can get rid of all overflows, ple_window_actual_max
(PW_effective_max?) is going to be set to
"ple_window_max [/-] ple_window_grow" in v2.
> (I think the || in the first "if" can be eliminated with some creativity
> in clamp_ple_window_max).
To do it, we'll want to intercept changes to ple_window as well.
(I disliked this patch a lot even before :)
next prev parent reply other threads:[~2014-08-20 12:41 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-19 20:35 [PATCH 0/9] Dynamic Pause Loop Exiting window Radim Krčmář
2014-08-19 20:35 ` [PATCH 1/9] KVM: add kvm_arch_sched_in Radim Krčmář
2014-08-20 7:47 ` Christian Borntraeger
2014-08-20 12:56 ` Radim Krčmář
2014-08-19 20:35 ` [PATCH 2/9] KVM: x86: introduce sched_in to kvm_x86_ops Radim Krčmář
2014-08-19 20:35 ` [PATCH 3/9] KVM: VMX: make PLE window per-vcpu Radim Krčmář
2014-08-20 7:13 ` Paolo Bonzini
2014-08-20 12:26 ` Radim Krčmář
2014-08-19 20:35 ` [PATCH 4/9] KVM: VMX: dynamise PLE window Radim Krčmář
2014-08-19 20:35 ` [PATCH 5/9] KVM: VMX: clamp " Radim Krčmář
2014-08-20 7:18 ` Paolo Bonzini
2014-08-20 12:46 ` Radim Krčmář
2014-08-19 20:35 ` [PATCH 6/9] KVM: trace kvm_ple_window grow/shrink Radim Krčmář
2014-08-19 20:35 ` [PATCH 7/9] KVM: VMX: abstract ple_window modifiers Radim Krčmář
2014-08-20 7:02 ` Paolo Bonzini
2014-08-20 12:25 ` Radim Krčmář
2014-08-19 20:35 ` [PATCH 8/9] KVM: VMX: runtime knobs for dynamic PLE window Radim Krčmář
2014-08-19 20:35 ` [PATCH 9/9] KVM: VMX: automatic PLE window maximum Radim Krčmář
2014-08-20 7:16 ` Paolo Bonzini
2014-08-20 7:18 ` Paolo Bonzini
2014-08-20 12:41 ` Radim Krčmář [this message]
2014-08-20 13:15 ` Paolo Bonzini
2014-08-20 15:31 ` Radim Krčmář
2014-08-20 15:34 ` Paolo Bonzini
2014-08-20 16:01 ` Radim Krčmář
2014-08-20 16:03 ` Paolo Bonzini
2014-08-20 16:26 ` Radim Krčmář
2014-08-21 6:48 ` [PATCH 0/9] Dynamic Pause Loop Exiting window Zhao, Hui-Zhi (Steven, HPservers-Core-OE-PSC)
2014-08-21 6:48 ` Zhao, Hui-Zhi (Steven, HPservers-Core-OE-PSC)
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