linux-kernel - Re: [PATCH v2 5/7] KVM: Introduce PV kick in flush tlb

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Message-ID: <87r4stckv5.fsf@linux.vnet.ibm.com>
Date:	Tue, 03 Jul 2012 13:55:02 +0530
From:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	peterz@...radead.org, mingo@...e.hu, avi@...hat.com,
	raghukt@...ux.vnet.ibm.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org, jeremy@...p.org,
	vatsa@...ux.vnet.ibm.com, hpa@...or.com
Subject: Re: [PATCH v2 5/7] KVM: Introduce PV kick in flush tlb

On Tue, 3 Jul 2012 05:07:13 -0300, Marcelo Tosatti <mtosatti@...hat.com> wrote:
> On Mon, Jun 04, 2012 at 10:38:17AM +0530, Nikunj A. Dadhania wrote:
> > In place of looping continuously introduce a halt if we do not succeed
> > after some time.
> > 
> > For vcpus that were running an IPI is sent.  In case, it went to sleep
> > between this, we will be doing flush_on_enter(harmless). But as a
> > flush IPI was already sent, that will be processed in ipi handler,
> > this might result into something undesireable, i.e. It might clear the
> > flush_mask of a new request.
> > 
> > So after sending an IPI and waiting for a while, do a halt and wait
> > for a kick from the last vcpu.
> > 
> > Signed-off-by: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
> > Signed-off-by: Nikunj A. Dadhania <nikunj@...ux.vnet.ibm.com>
> 
> Again, was it determined that this is necessary from data of 
> benchmarking on the in-guest-mode/out-guest-mode patch?
> 
No, this is more of a fix wrt algo.

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