--- title: JVM on Unikernel Nanos — GC trade-offs and heap uncommit description: Five HotSpot garbage collectors, Serial, Parallel, G1, ZGC, and Shenandoah, all run successfully on the Nanos unikernel using a standard Eclipse Temurin 25 JVM... canonical: https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: JVM on Unikernel Nanos — GC trade-offs and heap uncommit | daily.dev og:description: Five HotSpot garbage collectors, Serial, Parallel, G1, ZGC, and Shenandoah, all run successfully on the Nanos unikernel using a standard Eclipse Temurin 25 JVM... og:url: https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr og:image: https://api.daily.dev/og/posts/XIWGwg4rr.png og:image:alt: JVM on Unikernel Nanos — GC trade-offs and heap uncommit og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # JVM on Unikernel Nanos — GC trade-offs and heap uncommit **[Foojay.io](https://daily.dev/sources/foojayio)** · 14 min read · 1 upvotes · 0 comments ## Summary Five HotSpot garbage collectors, Serial, Parallel, G1, ZGC, and Shenandoah, all run successfully on the Nanos unikernel using a standard Eclipse Temurin 25 JVM with no modifications. Testing with the Renaissance page-rank benchmark on Oracle Cloud ARM64 reproduces trends from an earlier Akamas study on Linux: Parallel GC cuts execution time by 20.7% and peak heap by 38.2% versus G1, and ZGC achieves pauses around 0.04 ms. Heap uncommit also works: G1 repeatedly releases committed heap back to about 0.5 GB after garbage collection cycles, and ZGC and Shenandoah release memory too when uncommit is enabled via flags like -XX:ZUncommitDelay. Setting -Xms equal to -Xmx disables uncommit entirely. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Does ZGC's heap uncommit feature work when running Java on the Nanos unikernel? Yes, ZGC successfully uncommits unused heap memory on Nanos when enabled. In a test with -Xms1g -Xmx8g and -XX:ZUncommitDelay=5, the GC log recorded 20 Uncommitted events ranging from 4 to 468 MB each, totaling about 7.7 GB of cumulative uncommit, with committed heap fluctuating between 6.9 and 7.4 GB under continuous load. _Anyone sizing JVM heaps for unikernel or constrained deployments can track GC behavior details like this on daily.dev._ ### How much does switching from G1 to Parallel GC improve Java application performance? Switching from G1 to Parallel GC reduced execution time by 20.7% and peak heap usage by 38.2% in a Renaissance page-rank benchmark run on an ARM64 Nanos unikernel with Eclipse Temurin 25. This closely matches an earlier Akamas study on Linux with OpenJDK 15, which found a 22% reduction in execution time and 30% reduction in memory usage when switching from G1 to Parallel. _Developers picking a garbage collector for a Java workload can compare trade-offs like these on daily.dev._ ### Can I run a full JVM with G1, ZGC, or Shenandoah garbage collectors on a unikernel? Yes, all five major HotSpot garbage collectors, Serial, Parallel, G1, ZGC, and Shenandoah, run successfully on the Nanos unikernel using a standard Eclipse Temurin 25 distribution with no modifications to the JVM or collectors. ZGC and Shenandoah require nontrivial kernel memory-management support, including multiple mappings of the same physical memory and runtime memory commit and release, all of which Nanos supports. _Teams evaluating unikernels for Java workloads can follow JVM compatibility findings like this on daily.dev._ ## Similar posts on daily.dev - [foojay – a place for friends of OpenJDK](https://daily.dev/posts/foojay-a-place-for-friends-of-openjdk-fgo2ektwa) · Foojay.io · 0 upvotes · 0 comments - [JEP 545: Faster Startup and Warmup with ZGC](https://daily.dev/posts/jep-545-faster-startup-and-warmup-with-zgc-epicfdqv4) · Inside Java · 4 upvotes · 0 comments - [The Ultimate 10 Years Java Garbage Collection Guide \(2016–2026\) – Choosing the Right GC for Every Workload](https://daily.dev/posts/the-ultimate-10-years-java-garbage-collection-guide-2016-2026-choosing-the-right-gc-for-every-wo-gcjhfz5py) · Jakarta EE · 3 upvotes · 0 comments --- Tags: [#java](https://daily.dev/tags/java), [#jvm](https://daily.dev/tags/jvm) [View this post on daily.dev](https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"JVM on Unikernel Nanos — GC trade-offs and heap uncommit","url":"https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr"},"datePublished":"2026-10-28T00:51:11.892Z","dateModified":"2026-10-28T03:56:25.698Z","description":"Five HotSpot garbage collectors, Serial, Parallel, G1, ZGC, and Shenandoah, all run successfully on the Nanos unikernel using a standard Eclipse Temurin 25 JVM...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/e1910f12583ee8880490f4c5659583bb?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/e1910f12583ee8880490f4c5659583bb?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Foojay.io","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Foojay.io","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/1820f6a6ae944760aa322b67ed85f848","url":"https://daily.dev/sources/foojayio"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"java,jvm","timeRequired":"PT14M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Foojay.io","item":"https://daily.dev/sources/foojayio"},{"@type":"ListItem","position":3,"name":"JVM on Unikernel Nanos — GC trade-offs and heap uncommit"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/jvm-on-unikernel-nanos-gc-trade-offs-and-heap-uncommit-xiwgwg4rr#faq","mainEntity":[{"@type":"Question","name":"Does ZGC's heap uncommit feature work when running Java on the Nanos unikernel?","acceptedAnswer":{"@type":"Answer","text":"Yes, ZGC successfully uncommits unused heap memory on Nanos when enabled. 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