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 17:31:16 +0200 [thread overview]
Message-ID: <20140820153115.GA20453@potion.brq.redhat.com> (raw)
In-Reply-To: <53F49F80.1090408@redhat.com>
2014-08-20 15:15+0200, Paolo Bonzini:
> 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. :)
That code can't use PW directly, because PW_actual_max needs to be one
PW_grow below PW_max, so I'd rather enforce minimal PW_actual_max.
Btw. without extra code, we are still going to overflow on races when
changing PW_grow, should they be covered as well?
(+ There is a bug in this patch -- clamp_ple_window_max() should be
after param_set_int() ... damned unreviewed last-second changes.)
next prev parent reply other threads:[~2014-08-20 15:31 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
2014-08-20 13:15 ` Paolo Bonzini
2014-08-20 15:31 ` Radim Krčmář [this message]
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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