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https://issues.apache.org/jira/browse/ARROW-1795?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16256403#comment-16256403
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ASF GitHub Bot commented on ARROW-1795:
---------------------------------------
robertnishihara 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-345132214
cc @luchy0120
With this PR, it should be possible to do the following.
First start a plasma store with the `-f` flag
```
plasma_store -m 800000000 -s /tmp/store1 -f
```
Then
```python
import pyarrow.plasma as plasma
import numpy as np
c = plasma.connect('/tmp/store1', '', 64)
def create_and_release(size):
obj_id = plasma.ObjectID(np.random.bytes(20))
c.create(obj_id, size)
c.seal(obj_id)
create_and_release(5 * 10 ** 8)
create_and_release(6 * 10 ** 8)
```
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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: Lu Qi
> Priority: Minor
> Labels: pull-request-available
>
> 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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