From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: KVM: guest: only batch user pte updates
Date: Wed, 11 Feb 2009 08:57:42 -0800
Message-ID: <49930386.7070509@goop.org>
References: <20090210214532.GA4082@amt.cnet> <4991FD0D.1070108@goop.org> <20090210224141.GA4471@amt.cnet> <49920A68.5030408@goop.org> <4992BCD4.7040505@redhat.com>
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Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	kvm-devel <kvm@vger.kernel.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Zachary Amsden <zach@vmware.com>
To: Avi Kivity <avi@redhat.com>
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Avi Kivity wrote:
> Jeremy Fitzhardinge wrote:
>>>
>>> Yes. It seems however that only set_pte_at/pte_update/_defer are
>>> used under significatly long lazy mmu sections (long as in number of
>>> updates). Is it worthwhile to bother (and risk) batching kernel pte 
>>> updates ?
>>>   
>>
>> Well, that depends on how expensive each update is.  For something 
>> like kunmap atomic, I think combining the clear+tlb flush probably is 
>> worthwhile.
>
> I agree, kmap_atomic() is fairly common.

(Not that we're actually batching it at present; we need to work out 
proper semantics for nesting batches...)

    J