Date: Thu, 11 Jul 2013 13:56:31 +0300
From: Gleb Natapov <gleb@redhat.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Andrew Jones <drjones@redhat.com>, mingo@redhat.com, ouyang@cs.pitt.edu,
        habanero@linux.vnet.ibm.com, jeremy@goop.org, x86@kernel.org,
        konrad.wilk@oracle.com, hpa@zytor.com, pbonzini@redhat.com,
        linux-doc@vger.kernel.org, xen-devel@lists.xensource.com,
        peterz@infradead.org, mtosatti@redhat.com,
        stefano.stabellini@eu.citrix.com, andi@firstfloor.org,
        attilio.rao@citrix.com, gregkh@suse.de, agraf@suse.de,
        chegu_vinod@hp.com, torvalds@linux-foundation.org,
        avi.kivity@gmail.com, tglx@linutronix.de, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, riel@redhat.com,
        virtualization@lists.linux-foundation.org,
        srivatsa.vaddagiri@gmail.com
Subject: Re: [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks
Message-ID: <20130711105631.GH8575@redhat.com>
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 <20130710103325.GP24941@redhat.com>
 <51DE771F.7070805@linux.vnet.ibm.com>
 <20130711094833.GC8575@redhat.com>
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On Thu, Jul 11, 2013 at 04:23:58PM +0530, Raghavendra K T wrote:
> On 07/11/2013 03:41 PM, Gleb Natapov wrote:
> >On Thu, Jul 11, 2013 at 03:40:38PM +0530, Raghavendra K T wrote:
> >>>>>>Gleb,
> >>>>>>Can you elaborate little more on what you have in mind regarding per
> >>>>>>VM ple_window. (maintaining part of it as a per vm variable is clear
> >>>>>>to
> >>>>>>  me), but is it that we have to load that every time of guest entry?
> >>>>>>
> >>>>>Only when it changes, shouldn't be to often no?
> >>>>
> >>>>Ok. Thinking how to do. read the register and writeback if there need
> >>>>to be a change during guest entry?
> >>>>
> >>>Why not do it like in the patch you've linked? When value changes write it
> >>>to VMCS of the current vcpu.
> >>>
> >>
> >>Yes. can be done. So the running vcpu's ple_window gets updated only
> >>after next pl-exit. right?
> >I am not sure what you mean. You cannot change vcpu's ple_window while
> >vcpu is in a guest mode.
> >
> 
> I agree with that. Both of us are on the same page.
>  What I meant is,
> suppose the per VM ple_window changes when a vcpu x of that VM  was running,
> it will get its ple_window updated during next run.
Ah, I think "per VM" is what confuses me. Why do you want to have "per
VM" ple_windows and not "per vcpu" one? With per vcpu one ple_windows
cannot change while vcpu is running.

--
			Gleb.
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