From mboxrd@z Thu Jan  1 00:00:00 1970
From: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Subject: Re: [PATCH 0/8] KVM: Reduce mmu_lock hold time when zapping mmu
 pages
Date: Wed, 23 Jan 2013 23:49:05 +0900
Message-ID: <20130123234905.a982e78b52160a8bdf3f35f1@gmail.com>
References: <20130123191231.d66489d2.yoshikawa_takuya_b1@lab.ntt.co.jp>
	<50FFBF24.3000203@linux.vnet.ibm.com>
	<20130123222846.05bfc05a91ee133bd25981d6@gmail.com>
	<50FFE973.30709@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Cc: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>,
	mtosatti@redhat.com, gleb@redhat.com, kvm@vger.kernel.org
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mail-da0-f46.google.com ([209.85.210.46]:64835 "EHLO
	mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752463Ab3AWOtJ (ORCPT <rfc822;kvm@vger.kernel.org>);
	Wed, 23 Jan 2013 09:49:09 -0500
Received: by mail-da0-f46.google.com with SMTP id p5so3827813dak.33
        for <kvm@vger.kernel.org>; Wed, 23 Jan 2013 06:49:09 -0800 (PST)
In-Reply-To: <50FFE973.30709@linux.vnet.ibm.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Wed, 23 Jan 2013 21:45:23 +0800
Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> wrote:

> > The current code which deletes the two link nodes in different functions
> > looks unnatural to me: traversing the sp->link nodes forces us to break
> > the loop and sp->hash_link nodes alone is allowed to continue ...
> > 
> > Making each function semantically clear should be more important than
> > other things.
> > 
> 
> The reason the code like this is, we have lockless shadow page walker.

But hash_link needs to be protected by mmu_lock anyway?

> > But maybe a matter of taste, so I'll wait for the maintainers' comments.
> > 
> >> http://www.linux-kvm.org/page/TODO: O(1) mmu invalidation using a generation number
> >>
> >> I am doing this work for some weeks and will post the patch out during these days.
> > 
> > I remember that Avi originally wrote the idea of introducing the
> > generation of mmu pages in his other work.
> > 
> 
> Whatever the original consideration is, the idea can speed up mmu invalidation a lot.
> (Actually, i mentioned this idea to you when discussion fast write protect long time ago.)

It's fine.  I just wanted to know if my memory was correct.

	Takuya