linux-kernel - Re: [PATCH v2 4/6] KVM: VMX: dynamise PLE window

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Date:	Thu, 21 Aug 2014 13:54:05 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Gleb Natapov <gleb@...nel.org>,
	Raghavendra KT <raghavendra.kt@...ux.vnet.ibm.com>,
	Vinod Chegu <chegu_vinod@...com>,
	Hui-Zhi <hui-zhi.zhao@...com>,
	Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH v2 4/6] KVM: VMX: dynamise PLE window

2014-08-21 10:26+0200, Paolo Bonzini:
> Il 20/08/2014 22:53, Radim Krčmář ha scritto:
> > +static int __shrink_ple_window(int val, int shrinker, int minimum)
> 
> s/shrinker/factor/ or s/shrinker/param/ (shrinker has another meaning in
> the kernel).

True, thanks.

> > +{
> > +	if (shrinker < 1)
> > +		return ple_window;
> > +
> > +	if (shrinker < ple_window)
> > +		val /= shrinker;
> > +	else
> > +		val -= shrinker;
> > +
> > +	return max(val, minimum);
> 
> Any reason to use anything but ple_window as the minimum, even in
> update_ple_window_actual_max?

ple_window_actual_max needs to be one grow below the ple_window_max, so
it can be lower than ple_window.

> > +}
> > +
> > +static void modify_ple_window(struct kvm_vcpu *vcpu, int grow)
> > +{
> > +	struct vcpu_vmx *vmx = to_vmx(vcpu);
> > +	int new;
> > +
> > +	if (grow)
> > +		new = __grow_ple_window(vmx->ple_window);
> > +	else
> > +		new = __shrink_ple_window(vmx->ple_window, ple_window_shrink,
> > +		                          ple_window);
> > +
> > +	vmx->ple_window = max(new, ple_window);
> > +}
> > +#define grow_ple_window(vcpu)   modify_ple_window(vcpu, 1)
> > +#define shrink_ple_window(vcpu) modify_ple_window(vcpu, 0)
> 
> No macros please. :)

Guity as charged.
Using 0/1 or true/false in this context directly would be pretty bad ...
Is enum fine? (SHIRINK_PLE_WINDOW, GROW_PLE_WINDOW?)

(I can always make it into function pointers ;)
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