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From "Chen Luo (Jira)" <j...@apache.org>
Subject [jira] [Created] (ASTERIXDB-2715) Dynamic Memory Component Architecture
Date Thu, 16 Apr 2020 00:57:00 GMT
Chen Luo created ASTERIXDB-2715:
-----------------------------------

             Summary: Dynamic Memory Component Architecture
                 Key: ASTERIXDB-2715
                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-2715
             Project: Apache AsterixDB
          Issue Type: Improvement
          Components: STO - Storage
            Reporter: Chen Luo
            Assignee: Chen Luo


AsterixDB uses a static memory component management architecture by dividing the write memory
budget evenly to the active datasets. This leads to low memory utilization and cannot support
a large number of active datasets efficiently. To address this problem, we introduce a dynamic
memory memory component architecture, which has the following design decisions:
* All write memory pages are managed via a global virtual buffer cache (global VBC). Each
memory component simply requests pages from this global VBC upon writes and return pages unpon
flushes. Thus, memory allocation is fully dynamic and on-demand and there is no need for pre-allocating
write memory.
* The global VBC keeps track of the list of the primary LSM-trees across all partitions. Whenever
the write memory is nearly full, it selects one primary LSM-tree and flushes it as well as
its secondary indexes to disk. Currently we only flush one LSM-tree partition at a time. By
doing so, the reclaimed memory can be used by other components and this in turns increases
the memory utilization. 
* For datasets with filters, using large memory components may hurt query performance. Thus,
we additionally introduce a parameter to control the maximum memory component size for filtered
datasets. 



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