Hi Azuryy: Thanks so much for sharing. This gives me a good list of tuning options to read more on while constructing our GC_OPTS.
Follow up question: Was your cluster tuned to handle read heavy loads or was it mixed / read-write loads? Just trying to understand what your constraints were. --Suraj On Mon, Jul 8, 2013 at 10:52 PM, Azuryy Yu <[email protected]> wrote: > This is my HBASE GC options of CMS, it does work well. > > XX:+DisableExplicitGC -XX:+UseCompressedOops -XX:PermSize=160m > -XX:MaxPermSize=160m -XX:GCTimeRatio=19 -XX:SoftRefLRUPolicyMSPerMB=0 > -XX:SurvivorRatio=2 -XX:MaxTenuringThreshold=1 -XX:+UseFastAccessorMethods > -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled > -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSCompactAtFullCollection > -XX:CMSFullGCsBeforeCompaction=0 -XX:+CMSClassUnloadingEnabled > -XX:CMSMaxAbortablePrecleanTime=300 -XX:+CMSScavengeBeforeRemark > > > > On Tue, Jul 9, 2013 at 1:12 PM, Otis Gospodnetic < > [email protected] > > wrote: > > > Hi, > > > > Check http://blog.sematext.com/2013/06/24/g1-cms-java-garbage-collector/ > > > > Those graphs show RegionServer before and after switch to G1. The > > dashboard screenshot further below shows CMS (top row) vs. G1 (bottom > > row). After those tests we ended up switching to G1 across the whole > > cluster and haven't had issues or major pauses since.... knock on > > keyboard. > > > > Otis > > -- > > Solr & ElasticSearch Support -- http://sematext.com/ > > Performance Monitoring -- http://sematext.com/spm > > > > > > > > On Mon, Jul 8, 2013 at 2:56 PM, Stack <[email protected]> wrote: > > > On Mon, Jul 8, 2013 at 11:09 AM, Suraj Varma <[email protected]> > > wrote: > > > > > >> Hello: > > >> We have an HBase cluster with region servers running on 8GB heap size > > with > > >> a 0.6 block cache (it is a read heavy cluster, with bursty write > traffic > > >> via MR jobs). (version: hbase-0.94.6.1) > > >> > > >> During HBaseCon, while speaking to a few attendees, I heard some folks > > were > > >> running region servers as high as 24GB and some others in the 16GB > > range. > > >> > > >> So - question: Are there any special GC recommendations (tuning > > parameters, > > >> flags, etc) that folks who run at these large heaps can recommend > while > > >> moving up from an 8GB heap? i.e. for 16GB and for 24GB RS heaps ... ? > > >> > > >> I'm especially concerned about long pauses causing zk session timeouts > > and > > >> consequent RS shutdowns. Our boxes do have a lot of RAM and we are > > >> exploring how we can use more of it for the cluster while maintaining > > >> overall stability. > > >> > > >> Also - if there are clusters running multiple region servers per host, > > I'd > > >> be very interested to know what RS heap sizes those are being run at > ... > > >> and whether this was chosen as an alternative to running a single RS > > with > > >> large heap. > > >> > > >> (I know I'll have to test the GC stuff out on my cluster and for my > > >> workloads anyway ... but just trying to get a feel of what sort of > > tuning > > >> options had to be used to have a stable HBase cluster with 16 or 24GB > RS > > >> heaps). > > >> > > > > > > > > > You hit full GC in this 8G heap Suraj? Can you try running one server > at > > > 24G to see how it does (with GC logging enabled so you can watch it > over > > > time)? On one hand, more heap may make it so you avoid full GC -- if > you > > > are hitting them now at 8G -- because application has more head room. > On > > > other hand, yes, if a full GC hits, it will be gone for proportionally > > > longer than for your 8G heap. > > > > > > St.Ack > > >
