JDK-6916330 : CMS/G1: gc pause latency/scalability concern for flushing deferred card marks single-threaded
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs17
  • Priority: P5
  • Status: Closed
  • Resolution: Won't Fix
  • OS: generic
  • CPU: generic
  • Submitted: 2010-01-12
  • Updated: 2016-02-19
  • Resolved: 2016-02-19
Related Reports
Relates :  
JDK-6896647 - card marks can be deferred too long
Description
The fix for 6896647 moves the deferred card-mark flushing into the single-threaded prologue of GC, which can theoreticaly at least be a bottleneck to GC pause latency scalability and cause the occasional long GC pause. This can be addressed by means of GC recognizing the deferred card marks as a special modified reference set, amenable to parallel and concurrent processing.
Comments
Would it be useful, for G1 to at least add logging for this phase to find potential problems? (Or create a new CR?) I do not see this as a high priority issue, but if that deferred object is a large object array, we might run into problems, so it may be okay to leave the issue as is. Just asking.
19-02-2016
ILW: I: low -> theoretical problem L: low -> no known reproducer W: high -> none -> P5 for now
02-09-2014
WORK AROUND -XX:-ReduceInitialCardMarks which however may detract from mutator throughput when cache pressure is high.
12-01-2010
EVALUATION Yes, more scalable, lower pause latency and variance would be better.
12-01-2010
SUGGESTED FIX As in description field.
12-01-2010