[
https://issues.apache.org/jira/browse/CASSANDRA-5661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13693612#comment-13693612
]
Pavel Yaskevich commented on CASSANDRA-5661:
--------------------------------------------
It seems like we are trying to address different problems of what is in
description to the ticket and what Jeremia pointed out. Let me describe what
I'm trying to solve: When reading from multiple SSTables for a while and then
pattern changes and load is switched to the different subset of SSTables,
previous [C]RAR instances are returned to the appropriate queues and stuck
there until each SSTable is deallocated (by compaction) which creates memory
pressure on stale workloads or when compaction is running behind.
LRU could solve that problem when we have limit on total amount of memory that
we can use so it would start kicking in only after we reach that limit and
create a jitter in the queue and processing latencies.
What I propose adds minimal booking overhead per queue and expires items
quicker than LRU and more precise, also I'm not really worried about max number
of items in the queue per SSTable as it's organically limited to the number of
concurrent readers.
> Discard pooled readers for cold data
> ------------------------------------
>
> Key: CASSANDRA-5661
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5661
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 1.2.1
> Reporter: Jonathan Ellis
> Assignee: Pavel Yaskevich
> Fix For: 1.2.7
>
>
> Reader pooling was introduced in CASSANDRA-4942 but pooled
> RandomAccessReaders are never cleaned up until the SSTableReader is closed.
> So memory use is "the worst case simultaneous RAR we had open for this file,
> forever."
> We should introduce a global limit on how much memory to use for RAR, and
> evict old ones.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
