Rajesh Balamohan created HIVE-24061:
---------------------------------------
Summary: Improve llap task scheduling for better cache hit rate
Key: HIVE-24061
URL: https://issues.apache.org/jira/browse/HIVE-24061
Project: Hive
Issue Type: Improvement
Reporter: Rajesh Balamohan
TaskInfo is initialized with the "requestTime and locality delay". When lots of
vertices are in the same level, "taskInfo" details would be available upfront.
By the time, it gets to scheduling, "requestTime + localityDelay" won't be
higher than current time. Due to this, it misses scheduling delay details and
ends up choosing random node. This ends up missing cache hits and reads data
from remote storage.
E.g Observed this pattern in Q75 of tpcds.
Related lines of interest in scheduler:
[https://github.com/apache/hive/blob/master/llap-tez/src/java/org/apache/hadoop/hive/llap/tezplugins/LlapTaskSchedulerService.java
|https://github.com/apache/hive/blob/master/llap-tez/src/java/org/apache/hadoop/hive/llap/tezplugins/LlapTaskSchedulerService.java]
{code:java}
boolean shouldDelayForLocality =
request.shouldDelayForLocality(schedulerAttemptTime);
..
..
boolean shouldDelayForLocality(long schedulerAttemptTime) {
return localityDelayTimeout > schedulerAttemptTime;
}
{code}
Ideally, "localityDelayTimeout" should be adjusted based on it's first
scheduling opportunity.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
