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https://issues.apache.org/jira/browse/CASSANDRA-7882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14122706#comment-14122706
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Jay Patel edited comment on CASSANDRA-7882 at 9/5/14 9:12 AM:
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Is this overhead from using jemalloc allocator, or this happens with native gcc
as well? BTW, I've opened a related ticket CASSANDRA-7883 to allow plugging
jemalloc. And, CASSANDRA-7884 to make the region size configurable. May be I
should take care of all by one tix.
I think logarithmically scaling from 1K to 1 MB option can also work. But,
should we keep the start & end region-size configurable? Usually, this will be
advanced option to tune but very helpful. By default, we can keep 1 MB region
size as most use cases will not need to pack many tables.
Let me know the best way to handle this, and also you can assign it to me to
have it in 2.1.1. We're actually quite dependent on this as currently 1 MB is
putting a upper limit on number of tables in the cluster & having multiple
under-utilized clusters to support high # of tables is not cost-effective.
was (Author: pateljay3001):
Is this overhead from using jemalloc allocator, or this happens with native gcc
as well? BTW, I've opened a related ticket CASSANDRA-7883 to allow plugging
jemalloc. And, CASSANDRA-7884 to make the region size configurable.
I think logarithmically scaling from 1K to 1 MB option can also work. But,
should we keep the start & end region-size configurable? Usually, this will be
advanced option to tune but very helpful. By default, we can keep 1 MB region
size as most use cases will not need to pack many tables.
Let me know the best way to handle this, and also you can assign it to me to
have it in 2.1.1. We're actually quite dependent on this as currently 1 MB is
putting a upper limit on number of tables in the cluster & having multiple
under-utilized clusters to support high # of tables is not cost-effective.
> Allow disabling slab allocation for off-heap memtables
> ------------------------------------------------------
>
> Key: CASSANDRA-7882
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7882
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jay Patel
> Fix For: 2.1.1
>
>
> CASSANDRA-5935 allows option to disable region-based allocation for on-heap
> memtables but there is no option to disable it for off-heap memtables
> (memtable_allocation_type: offheap_objects).
> Disabling region-based allocation will allow us to pack more tables in the
> schema since minimum of 1MB region won't be allocated per table. Downside can
> be more fragmentation which should be controllable by using better allocator
> like JEMalloc.
> How about below option in yaml?:
> memtable_allocation_type: unslabbed_offheap_objects
> Thanks.
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