[ https://issues.apache.org/jira/browse/MAPREDUCE-1904?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Rajesh Balamohan updated MAPREDUCE-1904: ---------------------------------------- Attachment: MAPREDUCE-1904-trunk.patch Attaching the patch for trunk version. > Reducing locking contention in TaskTracker.MapOutputServlet's > LocalDirAllocator > ------------------------------------------------------------------------------- > > Key: MAPREDUCE-1904 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-1904 > Project: Hadoop Map/Reduce > Issue Type: Improvement > Components: tasktracker > Affects Versions: 0.20.1 > Reporter: Rajesh Balamohan > Attachments: MAPREDUCE-1904-RC10.patch, MAPREDUCE-1904-trunk.patch, > profiler output after applying the patch.jpg, TaskTracker- yourkit profiler > output .jpg, Thread profiler output showing contention.jpg > > > While profiling tasktracker with Sort benchmark, it was observed that threads > block on LocalDirAllocator.getLocalPathToRead() in order to get the index > file and temporary map output file. > As LocalDirAllocator is tied up with ServetContext, only one instance would > be available per tasktracker httpserver. Given the jobid & mapid, > LocalDirAllocator retrieves index file path and temporary map output file > path. getLocalPathToRead() is internally synchronized. > Introducing a LRUCache for this lookup reduces the contention heavily > (LRUCache with key =jobid +mapid and value=PATH to the file). Size of the > LRUCache can be varied based on the environment and I observed a throughput > improvement in the order of 4-7% with the introduction of LRUCache. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.