From: Izik Eidus <izik.eidus@ravellosystems.com>
To: Ni zhan Chen <nizhan.chen@gmail.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Petr Holasek <pholasek@redhat.com>,
Hugh Dickins <hughd@google.com>,
Chris Wright <chrisw@sous-sol.org>,
Rik van Riel <riel@redhat.com>
Subject: Re: ksm questions
Date: Wed, 24 Oct 2012 14:20:08 +0200 [thread overview]
Message-ID: <5087DCF8.6080205@ravellosystems.com> (raw)
In-Reply-To: <5087DC00.6070408@gmail.com>
On 10/24/2012 02:16 PM, Ni zhan Chen wrote:
> 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?
Talking from far memory, I remember it was easier/cleaner to only
support anonymous pages, until Andrea/Huge won`t remind us why I can`t
answer this
(Maybe later I will have some time to read a little bit the code again
and to remember what is going on in linux VM...)
>
>>
>>>
>>>>
>>>>>
>>>>> Thanks in advance. :-)
>>>>>
>>>>> Regards,
>>>>> Chen
>>>>>
>>>>
>>>>
>>>
>>
>>
>
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next prev parent reply other threads:[~2012-10-24 12:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-24 11:19 ksm questions Ni zhan Chen
2012-10-24 11:46 ` Izik Eidus
2012-10-24 11:59 ` Ni zhan Chen
2012-10-24 12:02 ` Izik Eidus
2012-10-24 12:16 ` Ni zhan Chen
2012-10-24 12:20 ` Izik Eidus [this message]
2012-10-24 12:35 ` Ni zhan Chen
2012-10-24 12:40 ` Ni zhan Chen
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