Re: ksm questions

[Ni zhan Chen <nizhan.chen@gmail.com>]

On 10/24/2012 08:02 PM, Izik Eidus wrote:
> On 10/24/2012 01:59 PM, Ni zhan Chen wrote:
>> On 10/24/2012 07:46 PM, Izik Eidus wrote:
>>> On 10/24/2012 01:19 PM, Ni zhan Chen wrote:
>>>> Hi all,
>>>>
>>>> I have some questions about ksm.
>>>>
>>>> 1) khugepaged default nice value is 19, but ksmd default nice value 
>>>> is 5, why this big different?
>>>> 2) why ksm doesn't support pagecache and tmpfs now? What's the 
>>>> bottleneck?
>>>> 3) ksm kernel doc said that "KSM only merges anonymous(private) 
>>>> pages, never pagecache(file) pages". But where judege it should be 
>>>> private?
>>>> 4) ksm kernel doc said that "To avoid the instability and the 
>>>> resulting false negatives to be permanent, KSM re-initializes the 
>>>> unstable tree root node to an empty tree, at every KSM pass." But I 
>>>> can't find where re-initializes the unstable tree, could you 
>>>> explain me?
>>>
>>>
>>> in scan_get_next_rmap_item(), if (slot == &ksm_mm_head) then we do 
>>> root_unstable_tree = RB_ROOT; this will result in root_unstable_tree 
>>> being empty.
>>
>> thanks Izik, what about the other three questions?
>
> Question number 2 is beacuse it is forced to work with anonymous 
> pages, about question 3 - I will have to remember why from the very 
> begining I wrote it to support only anonymous pages (few years have 
> been passed), maybe Andrea/Huge have it more hot in their heads?

The initialize goal of design ksm is for virtualization, but now it also 
can be used for other apps. So can it also support tmpfs or pagecache in 
the future?

>
>>
>>>
>>>>
>>>> Thanks in advance. :-)
>>>>
>>>> Regards,
>>>> Chen
>>>>
>>>
>>>
>>
>
>

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