linux-kernel - Re: [RFC] calc_memmap_size() isn't accurate and one suggestion to improve

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Date:   Sun, 9 Apr 2017 09:44:57 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Wei Yang <richard.weiyang@...il.com>, mgorman@...hsingularity.net,
        jiang.liu@...ux.intel.com, akpm@...ux-foundation.org,
        tj@...nel.org, mingo@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] calc_memmap_size() isn't accurate and one suggestion to
 improve

On Mon, Apr 03, 2017 at 11:18:19AM +0200, Michal Hocko wrote:
>On Tue 28-03-17 09:11:37, Wei Yang wrote:
>> Hi, masters,
>> 
>> # What I found
>> 
>> I found the function calc_memmap_size() may not be that accurate to get the
>> pages for memmap.
>> 
>> The reason is:
>> 
>> > memmap is allocated on a node base,
>> > while the calculation is on a zone base
>> 
>> This applies both to SPARSEMEM and FLATMEM.
>> 
>> For example, on my laptop with 6G memory, all the memmap space is allocated
>> from ZONE_NORMAL.
>
>Please try to be more specific. Why is this a problem? Are you trying to
>fix some bad behavior or you want to make it more optimal?
>
>I am sorry I didn't look closer into your proposal but I am quite busy
>and other people are probably in a similar situation. If you want to get
>a proper feedback please try to state the problem and be explicit if it
>is user observable.

Michal

Glad to hear from you.

Sure, let me do more investigation on this and try some experiment to see
whether this change is observable.

Have a nice day~

>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me

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