Baohe Zhang created SPARK-32350:
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             Summary: Add batch write support on LevelDB to improve performance 
of HybridStore
                 Key: SPARK-32350
                 URL: https://issues.apache.org/jira/browse/SPARK-32350
             Project: Spark
          Issue Type: Improvement
          Components: Web UI
    Affects Versions: 3.0.1, 3.1.0
            Reporter: Baohe Zhang


The idea is to improve the performance of HybridStore by adding batch write 
support to LevelDB. https://issues.apache.org/jira/browse/SPARK-31608 
introduces HybridStore. HybridStore will write data to InMemoryStore at first 
and use a background thread to dump data to LevelDB once the writing to 
InMemoryStore is completed. In the comments section of 
[https://github.com/apache/spark/pull/28412], Mridul Muralidharan mentioned 
using batch writing can improve the performance of this dumping process and he 
wrote the code of writeAll().

I did the comparison of the HybridStore switching time between one-by-one write 
and batch write on an HDD disk. When the disk is free, the batch-write has 
around 25% improvement, and when the disk is 100% busy, the batch-write has 7x 
- 10x improvement.

when the disk is at 0% utilization:

 
||log size, jobs and tasks per job||original switching time, with 
write()||switching time with writeAll()||
|133m, 400 jobs, 100 tasks per job|16s|13s|
|265m, 400 jobs, 200 tasks per job|30s|23s|
|1.3g, 1000 jobs, 400 tasks per job|136s|108s|

 

when the disk is at 100% utilization:
||log size, jobs and tasks per job||original switching time, with 
write()||switching time with writeAll()||
|133m, 400 jobs, 100 tasks per job|116s|17s|
|265m, 400 jobs, 200 tasks per job|251s|26s|

I also ran some write related benchmarking tests on LevelDBBenchmark.java and 
measured the total time of writing 1024 objects. The test was conducted when 
disk at 0% utilization.
||Benchmark test||with write(), ms||with writeAll(), ms||
|randomUpdatesIndexed|230.386|180.817|
|randomUpdatesNoIndex|58.935|50.113|
|randomWritesIndexed|315.241|254.400|
|randomWritesNoIndex|96.709|41.164|
|sequentialUpdatesIndexed|89.971|70.387|
|sequentialUpdatesNoIndex|72.021|53.769|
|sequentialWritesIndexed|103.052|67.358|
|sequentialWritesNoIndex|76.194|99.037|



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