Comments on: Drastically reducing GC pause times for YQL

By: Alberto Acevedo

Alberto Acevedo — Fri, 18 Jun 2010 19:06:22 +0000

I found some GC secrets that I want to share with you. Your article was the key to solve the out of memory errors problems with my Tomcat server. You can see my JVM settings in my blog: http://wp.me/pq115-1

Thanks for sharing,

Alberto

By: spullara

spullara — Sat, 22 May 2010 05:26:49 +0000

I often like to keep those in for diagnosis when Ops shows up and asks why something was unresponsive.

By: Chirag Shah

Chirag Shah — Sat, 22 May 2010 00:55:17 +0000

You can probably remove -XX:+PrintGCDetails -XX:+PrintGCTimeStamps for prod environments

By: spullara

spullara — Sun, 08 Nov 2009 00:05:43 +0000

Could it be the type of workloads you are throwing at it? We've had 30 VMs under load in production for the last week with great, low pause times without a hint of instability. I'll take a crack at it with your options and see what we see. G1 so far has been useless with full pauses being long and frequent under moderate testing. Ran a 24 hour test last night of JRockit and their deterministic GC with excellent results for our workloads. We also don't use Solaris. It is all RHEL.

By: spullara

spullara — Sat, 07 Nov 2009 16:05:43 +0000

By: Ari Zilka

Ari Zilka — Sat, 07 Nov 2009 02:54:30 +0000

Uhm, our work with the JVM shows Concurrent collector highly unstable and several folks in high places who shall remain nameless say never to use it. Also, OS / platform is important. On Solaris / CMT, run LargePageSizes and about as many ParallelGC threads as you have CMT threads (32, 64, or 128).

-XX:SurvivorRatio=8 – large survivor spaces for short-lived objects
-XX:+UseParallelGC
-XX:ParallelGCThreads=20
-XX:+UseParallelOldGC
-Xmn1g
-server switch

Last, if you insist on CMS, then we have used ParNewGC + CMS and initiatingOccupancyFraction to get the GC to kick off aggressively and keep down the Full pauses.

G1 is going to have to dig us all out of the whole the CMS is burying us in, but Parallel w/ LOTS of threads has proved way more stable for us w/o the stop-the-worlds from CMS that can be like 3 hours...

By: spullara

spullara — Wed, 04 Nov 2009 13:08:38 +0000

We are currently on java version 1.6.0_16. We haven't yet seen a crash with this configuration.

By: Amit Naik

Amit Naik — Wed, 04 Nov 2009 07:02:33 +0000

Which specific version of 1.6 are you using? We have seen some GC related crashes with 1.6_06, 14,15 while using the CMS collector so we switched back to using the throughput collector. Did you happen to run into this?

By: h0h0h0

h0h0h0 — Wed, 04 Nov 2009 03:04:47 +0000

Tight. I love the black magic that you can get with some of the JVM parameters. It's a whole new world over them thar hills.