Ah, yes - thanks for the clarification. Didn't pay attention to how ambiguously I was using "supported" there :)
Bill Au wrote: > SUN has recently clarify the issue regarding "unsupported unless you pay" > for the G1 garbage collector. Here is the updated release of Java 6 update > 14: > http://java.sun.com/javase/6/webnotes/6u14.html > > > G1 will be part of Java 7, fully supported without pay. The version > included in Java 6 update 14 is a beta release. Since it is beta, SUN does > not recommend using it unless you have a support contract because as with > any beta software there will be bugs. Non paying customers may very well > have to wait for the official version in Java 7 for bug fixes. > > Here is more info on the G1 garbage collector: > > http://java.sun.com/javase/technologies/hotspot/gc/g1_intro.jsp > > > Bill > > On Sat, Oct 3, 2009 at 1:28 PM, Mark Miller <markrmil...@gmail.com> wrote: > > >> Another option of course, if you're using a recent version of Java 6: >> >> try out the beta-ish, unsupported unless you pay, G1 garbage collector. >> I've only recently started playing with it, but its supposed to be much >> better than CMS. Its supposedly got much better throughput, its much >> better at dealing with fragmentation issues (CMS is actually pretty bad >> with fragmentation come to find out), and overall its just supposed to >> be a very nice leap ahead in GC. Havn't had a chance to play with it >> much myself, but its supposed to be fantastic. A whole new approach to >> generational collection for Sun, and much closer to the "real time" GC's >> available from some other vendors. >> >> Mark Miller wrote: >> >>> siping liu wrote: >>> >>> >>>> Hi, >>>> >>>> I read pretty much all posts on this thread (before and after this one). >>>> >> Looks like the main suggestion from you and others is to keep max heap size >> (-Xmx) as small as possible (as long as you don't see OOM exception). This >> brings more questions than answers (for me at least. I'm new to Solr). >> >>>> >>>> First, our environment and problem encountered: Solr1.4 (nightly build, >>>> >> downloaded about 2 months ago), Sun JDK1.6, Tomcat 5.5, running on >> Solaris(multi-cpu/cores). The cache setting is from the default >> solrconfig.xml (looks very small). At first we used minimum JAVA_OPTS and >> quickly run into the problem similar to the one orignal poster reported -- >> long pause (seconds to minutes) under load test. jconsole showed that it >> pauses on GC. So more JAVA_OPTS get added: "-XX:+UseConcMarkSweepGC >> -XX:+UseParNewGC -XX:ParallelGCThreads=8 -XX:SurvivorRatio=2 >> -XX:NewSize=128m -XX:MaxNewSize=512m -XX:MaxGCPauseMillis=200", the thinking >> is with mutile-cpu/cores we can get over with GC as quickly as possibe. With >> the new setup, it works fine until Tomcat reaches heap size, then it blocks >> and takes minutes on "full GC" to get more space from "tenure generation". >> We tried different Xmx (from very small to large), no difference in long GC >> time. We never run into OOM. >> >>>> >>> MaxGCPauseMillis doesnt work with UseConcMarkSweepGC - its for use with >>> the Parallel collector. That also doesnt look like a good survivorratio. >>> >>> >>>> Questions: >>>> >>>> * In general various cachings are good for performance, we have more RAM >>>> >> to use and want to use more caching to boost performance, isn't your >> suggestion (of lowering heap limit) going against that? >> >>>> >>> Leaving RAM for the FileSystem cache is also very important. But you >>> should also have enough RAM for your Solr caches of course. >>> >>> >>>> * Looks like Solr caching made its way into tenure-generation on heap, >>>> >> that's good. But why they get GC'ed eventually?? I did a quick check of Solr >> code (Solr 1.3, not 1.4), and see a single instance of using WeakReference. >> Is that what is causing all this? This seems to suggest a design flaw in >> Solr's memory management strategy (or just my ignorance about Solr?). I >> mean, wouldn't this be the "right" way of doing it -- you allow user to >> specify the cache size in solrconfig.xml, then user can set up heap limit in >> JAVA_OPTS accordingly, and no need to use WeakReference (BTW, why not >> SoftReference)?? >> >>>> >>> Do you see concurrent mode failure when looking at your gc logs? ie: >>> >>> 174.445: [GC 174.446: [ParNew: 66408K->66408K(66416K), 0.0000618 >>> secs]174.446: [CMS (concurrent mode failure): 161928K->162118K(175104K), >>> 4.0975124 secs] 228336K->162118K(241520K) >>> >>> That means you have still getting major collections with CMS, and you >>> don't want that. You might try kicking GC off earlier with something >>> like: -XX:CMSInitiatingOccupancyFraction=50 >>> >>> >>>> * Right now I have a single Tomcat hosting Solr and other applications. >>>> >> I guess now it's better to have Solr on its own Tomcat, given that it's >> tricky to adjust the java options. >> >>>> >>>> thanks. >>>> >>>> >>>> >>>> >>>> >>>> >>>>> From: wun...@wunderwood.org >>>>> To: solr-user@lucene.apache.org >>>>> Subject: RE: Solr and Garbage Collection >>>>> Date: Fri, 25 Sep 2009 09:51:29 -0700 >>>>> >>>>> 30ms is not better or worse than 1s until you look at the service >>>>> requirements. For many applications, it is worth dedicating 10% of your >>>>> processing time to GC if that makes the worst-case pause short. >>>>> >>>>> On the other hand, my experience with the IBM JVM was that the maximum >>>>> >> query >> >>>>> rate was 2-3X better with the concurrent generational GC compared to >>>>> >> any of >> >>>>> their other GC algorithms, so we got the best throughput along with the >>>>> shortest pauses. >>>>> >>>>> Solr garbage generation (for queries) seems to have two major >>>>> >> components: >> >>>>> per-request garbage and cache evictions. With a generational collector, >>>>> these two are handled by separate parts of the collector. Per-request >>>>> garbage should completely fit in the short-term heap (nursery), so that >>>>> >> it >> >>>>> can be collected rapidly and returned to use for further requests. If >>>>> >> the >> >>>>> nursery is too small, the per-request allocations will be made in >>>>> >> tenured >> >>>>> space and sit there until the next major GC. Cache evictions are almost >>>>> always in long-term storage (tenured space) because an LRU algorithm >>>>> guarantees that the garbage will be old. >>>>> >>>>> Check the growth rate of tenured space (under constant load, of course) >>>>> while increasing the size of the nursery. That rate should drop when >>>>> >> the >> >>>>> nursery gets big enough, then not drop much further as it is increased >>>>> >> more. >> >>>>> After that, reduce the size of tenured space until major GCs start >>>>> >> happening >> >>>>> "too often" (a judgment call). A bigger tenured space means longer >>>>> >> major GCs >> >>>>> and thus longer pauses, so you don't want it oversized by too much. >>>>> >>>>> Also check the hit rates of your caches. If the hit rate is low, say >>>>> >> 20% or >> >>>>> less, make that cache much bigger or set it to zero. Either one will >>>>> >> reduce >> >>>>> the number of cache evictions. If you have an HTTP cache in front of >>>>> >> Solr, >> >>>>> zero may be the right choice, since the HTTP cache is cherry-picking >>>>> >> the >> >>>>> easily cacheable requests. >>>>> >>>>> Note that a commit nearly doubles the memory required, because you have >>>>> >> two >> >>>>> live Searcher objects with all their caches. Make sure you have >>>>> >> headroom for >> >>>>> a commit. >>>>> >>>>> If you want to test the tenured space usage, you must test with real >>>>> >> world >> >>>>> queries. Those are the only way to get accurate cache eviction rates. >>>>> >>>>> wunder >>>>> >>>>> >>>>> >>>> _________________________________________________________________ >>>> Bing™ brings you maps, menus, and reviews organized in one place. Try >>>> >> it now. >> >> http://www.bing.com/search?q=restaurants&form=MLOGEN&publ=WLHMTAG&crea=TEXT_MLOGEN_Core_tagline_local_1x1 >> >>>> >>> >>> >> -- >> - Mark >> >> http://www.lucidimagination.com >> >> >> >> >> >> > > -- - Mark http://www.lucidimagination.com
