linux-kernel - Re: [PATCH 9/9] KVM: VMX: automatic PLE window maximum

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Date:	Wed, 20 Aug 2014 15:15:44 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krčmář <rkrcmar@...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>
Subject: Re: [PATCH 9/9] KVM: VMX: automatic PLE window maximum

Il 20/08/2014 14:41, Radim Krčmář ha scritto:
>> > 	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 :)

What about setting ple_window_actual_max to 0 if ple_window_grow is 0
(instead of just returning)?

Then the "if (ple_window_actual_max < ple_window)" will always fail and
you'll go through "new = ple_window".  But perhaps it's more gross and
worthless than creative. :)

Paolo
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