Re: [PATCH v3 07/15] KVM: MMU: introduce nulls desc

Xiao Guangrong
2013-11-28T08:32:22Z

On 11/27/2013 03:58 AM, Marcelo Tosatti wrote:
> On Tue, Nov 26, 2013 at 11:10:19AM +0800, Xiao Guangrong wrote:
>> On 11/25/2013 10:23 PM, Marcelo Tosatti wrote:
>>> On Mon, Nov 25, 2013 at 02:48:37PM +0200, Avi Kivity wrote:
>>>> On Mon, Nov 25, 2013 at 8:11 AM, Xiao Guangrong
>>>> <xiaoguangrong@linux.vnet.ibm.com> wrote:
>>>>>
>>>>> On Nov 23, 2013, at 3:14 AM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
>>>>
>>>> <snip complicated stuff about parent_pte>
>>>>
>>>> I'm not really following, but note that parent_pte predates EPT (and
>>>> the use of rcu in kvm), so all the complexity that is the result of
>>>> trying to pack as many list entries into a cache line can be dropped.
>>>> Most setups now would have exactly one list entry, which is handled
>>>> specially antyway.
>>>>
>>>> Alternatively, the trick of storing multiple entries in one list entry
>>>> can be moved to generic code, it may be useful to others.
>>>
>>> Yes, can the lockless list walking code be transformed into generic
>>> single-linked list walking? So the correctness can be verified
>>> independently, and KVM becomes a simple user of that interface.
>>
>> I'am afraid the signle-entry list is not so good as we expected. In my
>> experience, there're too many entries on rmap, more than 300 sometimes.
>> (consider a case that a lib shared by all processes).
>
> single linked list was about moving singly-linked lockless walking
> to generic code.
>
> http://www.spinics.net/lists/linux-usb/msg39643.html
> http://marc.info/?l=linux-kernel&m=103305635013575&w=3
>

Oh, i confused "single linked" and "single entry", sorry about that.