[
https://issues.apache.org/jira/browse/PIG-167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12581938#action_12581938
]
Pi Song commented on PIG-167:
-----------------------------
I've thought about this a bit more. There are two concerns here regarding
memory manager: reliability, and performance.
The purpose of experimenting this would be *to provide a more reliable
solution* (But don't degrade the performance) .
Any idea on how we can measure reliability?
> Experiment : A proper bag memory manager.
> -----------------------------------------
>
> Key: PIG-167
> URL: https://issues.apache.org/jira/browse/PIG-167
> Project: Pig
> Issue Type: Improvement
> Reporter: Pi Song
> Attachments: diagram.gif, MemManager0.patch
>
>
> According to PIG-164, I think we still have room for improvement:-
> 1) Alan said
> {quote}
> "It rests on the assumption that data bags generally live about the same
> amount of time, thus there won't be a long lived databag at the head of the
> list blocking the cleaning of many stale references later in the list."
> {quote}
> By looking at a line of code in SpillableMemoryManager
> {noformat}
> Collections.sort(spillables, new Comparator<WeakReference<Spillable>>() {
> {noformat}
> - Alan's assumption might be wrong after the memory manager tries to spill
> the list.
> - I don't understand why this has to be sorted and start spilling from the
> smallest bags first. Most file systems are not good at handling small files
> (specially ext2/ext3).
> 2) We use a linkedlist to maintain WeakReference. Normally a linkedlist
> consumes double as much memory that an array would consume(for pointers).
> Should it be better to change LinkedList to Array or ArrayList?
> 3) In SpillableMemoryManager, handleNotification which does a kind of I/O
> intensive job shares the same lock with registerSpillable. This doesn't seem
> to be efficient.
> 4) Sometimes I recognized that the bag currently in use got spilled and read
> back over and over again. Essentially, the memory manager should consider
> spilling bags currently not in use first.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
