[OAK-1042] Segment node store caching

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.10
• Assignee: Thomas Mueller
• Reporter: Thomas Mueller
• Created: 25/Sep/13 12:58
• Updated: 09/Oct/13 15:29
• Resolved: 02/Oct/13 19:09

Description

Segment node stores caching seems to use quite a lot of CPU. According to my test, the oak-run SimpleSearchTest uses about 50% for Segment node store caching, when using the built-in profiler:

java -mx1g -Dwarmup=3 -Druntime=15 -jar target/oak-run-*.jar benchmark SimpleSearchTest Oak-Tar
packages:
48%: com.google.common.cache <== cache
16%: org.apache.jackrabbit.oak.plugins.segment
8%: org.apache.jackrabbit.oak.plugins.memory
4%: org.apache.jackrabbit.oak.util
3%: org.apache.jackrabbit.oak.core
2%: org.apache.jackrabbit.oak.benchmark
2%: com.google.common.base   <== cache
.
Oak-Tar                          308     310     313     324     344      48

The problem seems to be the cache in the FileStore. As far as I see, the cache limit is 1000 <UUID, Segment> entries (size based, not weight based).

I wonder if there is a simple way to reduce CPU usage. I will try with the LIRS cache.

I also wonder if this cache should really be size limited, and not weight limited (segments can have different sizes as far as I know)?