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From: Marcelo Tosatti <mtosatti@redhat.com>
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Avi Kivity <avi.kivity@gmail.com>, Gleb Natapov <gleb@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 06/12] KVM: MMU: introduce a static table to map guest access to spte access
Date: Mon, 28 Jan 2013 23:07:58 -0200	[thread overview]
Message-ID: <20130129010758.GA12132@amt.cnet> (raw)
In-Reply-To: <20130129000715.GA10814@amt.cnet>

On Mon, Jan 28, 2013 at 10:07:15PM -0200, Marcelo Tosatti wrote:
> On Fri, Jan 25, 2013 at 10:46:31AM +0800, Xiao Guangrong wrote:
> > On 01/25/2013 08:15 AM, Marcelo Tosatti wrote:
> > > On Wed, Jan 23, 2013 at 06:07:20PM +0800, Xiao Guangrong wrote:
> > >> It makes set_spte more clean and reduces branch prediction
> > >>
> > >> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> > >> ---
> > >>  arch/x86/kvm/mmu.c |   37 ++++++++++++++++++++++++++-----------
> > >>  1 files changed, 26 insertions(+), 11 deletions(-)
> > > 
> > > Don't see set_spte as being a performance problem?
> > > IMO the current code is quite simple.
> > 
> > Yes, this is not a performance problem.
> > 
> > I just dislike this many continuous "if"-s in the function:
> > 
> > if (xxx)
> > 	xxx
> > if (xxx)
> > 	xxx
> > ....
> > 
> > Totally, it has 7 "if"-s before this patch.
> > 
> > Okay, if you think this is unnecessary, i will drop this patch. :)
> 
> Yes, please (unless you can show set_spte is a performance problem).

Same thing for spte fast drop: is it a performance problem? 

Please try to group changes into smaller, less controversial sets with 
a clear goal:

- Debated performance improvement.
- Cleanups (eg mmu_set_spte argument removal).
- Bug fixes.
- Performance improvements.

Thanks.


  reply	other threads:[~2013-01-29 11:14 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-23 10:04 [PATCH v2 01/12] KVM: MMU: lazily drop large spte Xiao Guangrong
2013-01-23 10:04 ` [PATCH v2 02/12] KVM: MMU: cleanup mapping-level Xiao Guangrong
2013-01-23 10:05 ` [PATCH v2 03/12] KVM: MMU: simplify mmu_set_spte Xiao Guangrong
2013-01-29  0:21   ` Marcelo Tosatti
2013-01-29  2:55     ` Xiao Guangrong
2013-01-29 21:53       ` Marcelo Tosatti
2013-01-30  3:22         ` Xiao Guangrong
2013-01-23 10:06 ` [PATCH v2 04/12] KVM: MMU: simplify set_spte Xiao Guangrong
2013-01-23 10:06 ` [PATCH v2 05/12] KVM: MMU: introduce vcpu_adjust_access Xiao Guangrong
2013-01-24 10:36   ` Gleb Natapov
2013-01-24 11:33     ` Xiao Guangrong
2013-01-23 10:07 ` [PATCH v2 06/12] KVM: MMU: introduce a static table to map guest access to spte access Xiao Guangrong
2013-01-25  0:15   ` Marcelo Tosatti
2013-01-25  2:46     ` Xiao Guangrong
2013-01-29  0:07       ` Marcelo Tosatti
2013-01-29  1:07         ` Marcelo Tosatti [this message]
2013-01-29 13:16           ` Gleb Natapov
2013-01-30  3:53           ` Xiao Guangrong
2013-01-23 10:07 ` [PATCH v2 07/12] KVM: MMU: remove pt_access in mmu_set_spte Xiao Guangrong
2013-01-23 10:08 ` [PATCH v2 08/12] KVM: MMU: cleanup __direct_map Xiao Guangrong
2013-01-23 10:09 ` [PATCH v2 09/12] KVM: MMU: introduce mmu_spte_establish Xiao Guangrong
2013-01-23 10:09 ` [PATCH v2 10/12] KVM: MMU: unify the code of walking pte list Xiao Guangrong
2013-01-27 13:28   ` Gleb Natapov
2013-01-29  3:01     ` Xiao Guangrong
2013-01-23 10:10 ` [PATCH v2 11/12] KVM: MMU: fix spte assertion Xiao Guangrong
2013-01-23 10:10 ` [PATCH v2 12/12] KVM: MMU: fast drop all spte on the pte_list Xiao Guangrong
2013-01-27 12:06 ` [PATCH v2 01/12] KVM: MMU: lazily drop large spte Gleb Natapov
2013-01-29  2:57   ` Xiao Guangrong

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