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https://issues.apache.org/jira/browse/ARROW-1795?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16256607#comment-16256607
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ASF GitHub Bot commented on ARROW-1795:
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pcmoritz commented on issue #1327: ARROW-1795: [Plasma] Create flag to make 
Plasma store use a single memory-mapped file.
URL: https://github.com/apache/arrow/pull/1327#issuecomment-345168882
 
 
   Yeah, there can be fragmentation, but the malloc implementation we use 
(written by doug lea) is designed to minimize fragmentation if possible, see 
http://g.oswego.edu/dl/html/malloc.html

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> [Plasma C++] change evict policy
> --------------------------------
>
>                 Key: ARROW-1795
>                 URL: https://issues.apache.org/jira/browse/ARROW-1795
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Plasma (C++)
>            Reporter: Lu Qi 
>            Assignee: Robert Nishihara
>            Priority: Minor
>              Labels: pull-request-available
>             Fix For: 0.8.0
>
>
> case 1.say, we have total free memory 8 G , we have input 5G data, then comes 
> another 6G data, 
> if we choose to evict space 6G , it will throw exception saying that
> no object can be free. This is because we didn't count the 3G remaining free
> space .If we count this remaining 3G , we need to ask only 3G,thus
> we can evict the 5G data and we are still alive . 
> case 2. another situation is :  if we have free memory 10G , we input 1.5G 
> data ,then comes another
> 9G data , if we use  10*20% = 2G data to evict ,then we will crash . In this 
> situation we need to 
> use 9+1.5-10 = 0.5G data to evict  



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