Ming LI created HAWQ-1030:
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Summary: User hang due to poor spin-lock/LWLock performance under
high concurrency
Key: HAWQ-1030
URL: https://issues.apache.org/jira/browse/HAWQ-1030
Project: Apache HAWQ
Issue Type: Bug
Components: Core
Reporter: Ming LI
Assignee: Lei Chang
Some clients have recently reported apparent hangs with their applications. In
all cases the symptoms were the same:
* All sessions appear to be hung in LWLockAcquire or Release, specifically
s_lock
* there is a high number of concurrent sessions (close to 100)
* System is not actually hung, normally processing resumes after some period of
time when all sessions have completed their locking work
The postgresql developer community has found several issues with performance
under high concurrency (> 32 sessions) in the spin-lock mechanism we've
inherited in HAWQ. This ultimately has been corrected in 9.5 with a replacement
to the spin-lock mechanism and appears to provide a significant boost to query
performance.
The actual fix is in commit: ab5194e6f617a9a9e7aadb3dd1cee948a42d0755
Only 1 line commit to s_lock.c could help address this and would be easy enough
to cherry-pick: b03d196be055450c7260749f17347c2d066b4254
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