{"id":443,"date":"2026-03-21T05:55:00","date_gmt":"2026-03-21T05:55:00","guid":{"rendered":"https:\/\/harshad-sonawane.com\/blog\/?p=443"},"modified":"2026-01-15T06:23:38","modified_gmt":"2026-01-15T06:23:38","slug":"java-garbage-collection-zgc-shenandoah-g1gc","status":"publish","type":"post","link":"https:\/\/harshad-sonawane.com\/blog\/java-garbage-collection-zgc-shenandoah-g1gc\/","title":{"rendered":"A Deep Dive into Java\u2019s Garbage Collection Algorithms (ZGC, Shenandoah, G1GC)"},"content":{"rendered":"<p data-start=\"360\" data-end=\"657\">Memory management has always been one of Java\u2019s strongest advantages\u2014and one of its most misunderstood components. While <a href=\"https:\/\/harshad-sonawane.com\/blog\/reduce-cloud-costs-java-applications\/\">Java<\/a> developers rarely manage memory manually, the <strong data-start=\"532\" data-end=\"583\">choice and tuning of the Garbage Collector (GC)<\/strong> can dramatically impact application latency, throughput, and scalability.<\/p>\n<p data-start=\"659\" data-end=\"814\">With modern JVMs offering multiple advanced collectors, understanding <strong data-start=\"729\" data-end=\"758\">G1GC, <a href=\"https:\/\/harshad-sonawane.com\/blog\/jvm-tuning-low-latency-applications\/\">ZGC<\/a>, and Shenandoah<\/strong> is no longer optional for performance-critical systems.<\/p>\n<p data-start=\"816\" data-end=\"988\">This article provides a <strong data-start=\"840\" data-end=\"870\">deep, practical comparison<\/strong> of these collectors, explaining <em data-start=\"903\" data-end=\"929\">how they work internally<\/em>, <em data-start=\"931\" data-end=\"949\">when to use them<\/em>, and <em data-start=\"955\" data-end=\"987\">what trade-offs they introduce<\/em>.<\/p>\n<hr data-start=\"990\" data-end=\"993\" \/>\n<h2 data-start=\"995\" data-end=\"1043\">Why Garbage Collection Matters in Modern Java<\/h2>\n<p data-start=\"1045\" data-end=\"1075\">As applications evolve toward:<\/p>\n<ul data-start=\"1076\" data-end=\"1179\">\n<li data-start=\"1076\" data-end=\"1093\">\n<p data-start=\"1078\" data-end=\"1093\"><a href=\"https:\/\/harshad-sonawane.com\/blog\/audit-logging-in-java-microservices-techniques-and-compliance-tips\/\">Microservices<\/a><\/p>\n<\/li>\n<li data-start=\"1094\" data-end=\"1118\">\n<p data-start=\"1096\" data-end=\"1118\">High-throughput APIs<\/p>\n<\/li>\n<li data-start=\"1119\" data-end=\"1150\">\n<p data-start=\"1121\" data-end=\"1150\">Low-latency trading systems<\/p>\n<\/li>\n<li data-start=\"1151\" data-end=\"1179\">\n<p data-start=\"1153\" data-end=\"1179\">Cloud-native deployments<\/p>\n<\/li>\n<\/ul>\n<p data-start=\"1181\" data-end=\"1210\">GC behavior directly affects:<\/p>\n<ul data-start=\"1211\" data-end=\"1321\">\n<li data-start=\"1211\" data-end=\"1238\">\n<p data-start=\"1213\" data-end=\"1238\">Tail latency (P99 \/ P999)<\/p>\n<\/li>\n<li data-start=\"1239\" data-end=\"1263\">\n<p data-start=\"1241\" data-end=\"1263\">Throughput consistency<\/p>\n<\/li>\n<li data-start=\"1264\" data-end=\"1281\">\n<p data-start=\"1266\" data-end=\"1281\">CPU utilization<\/p>\n<\/li>\n<li data-start=\"1282\" data-end=\"1321\">\n<p data-start=\"1284\" data-end=\"1321\">Cost efficiency in cloud environments<\/p>\n<\/li>\n<\/ul>\n<p data-start=\"1323\" data-end=\"1407\">A poorly chosen GC can introduce <strong data-start=\"1356\" data-end=\"1379\">multi-second pauses<\/strong>, even in well-written code.<\/p>\n<hr data-start=\"1409\" data-end=\"1412\" \/>\n<h2 data-start=\"1414\" data-end=\"1457\">The Evolution of Java Garbage Collectors<\/h2>\n<div class=\"TyagGW_tableContainer\">\n<div class=\"group TyagGW_tableWrapper flex flex-col-reverse w-fit\" tabindex=\"-1\">\n<table data-start=\"1459\" data-end=\"1684\" class=\"w-fit min-w-(--thread-content-width)\">\n<thead data-start=\"1459\" data-end=\"1493\">\n<tr data-start=\"1459\" data-end=\"1493\">\n<th data-start=\"1459\" data-end=\"1465\" data-col-size=\"sm\">Era<\/th>\n<th data-start=\"1465\" data-end=\"1477\" data-col-size=\"sm\">Collector<\/th>\n<th data-start=\"1477\" data-end=\"1493\" data-col-size=\"sm\">Primary Goal<\/th>\n<\/tr>\n<\/thead>\n<tbody data-start=\"1508\" data-end=\"1684\">\n<tr data-start=\"1508\" data-end=\"1552\">\n<td data-start=\"1508\" data-end=\"1519\" data-col-size=\"sm\">Java 5\u20137<\/td>\n<td data-start=\"1519\" data-end=\"1533\" data-col-size=\"sm\">Parallel GC<\/td>\n<td data-start=\"1533\" data-end=\"1552\" data-col-size=\"sm\">High throughput<\/td>\n<\/tr>\n<tr data-start=\"1553\" data-end=\"1588\">\n<td data-start=\"1553\" data-end=\"1564\" data-col-size=\"sm\">Java 7\u20138<\/td>\n<td data-start=\"1564\" data-end=\"1570\" data-col-size=\"sm\">CMS<\/td>\n<td data-start=\"1570\" data-end=\"1588\" data-col-size=\"sm\">Reduced pauses<\/td>\n<\/tr>\n<tr data-start=\"1589\" data-end=\"1629\">\n<td data-start=\"1589\" data-end=\"1599\" data-col-size=\"sm\">Java 9+<\/td>\n<td data-start=\"1599\" data-end=\"1606\" data-col-size=\"sm\">G1GC<\/td>\n<td data-start=\"1606\" data-end=\"1629\" data-col-size=\"sm\">Predictable latency<\/td>\n<\/tr>\n<tr data-start=\"1630\" data-end=\"1684\">\n<td data-start=\"1630\" data-end=\"1641\" data-col-size=\"sm\">Java 11+<\/td>\n<td data-start=\"1641\" data-end=\"1659\" data-col-size=\"sm\">ZGC, Shenandoah<\/td>\n<td data-start=\"1659\" data-end=\"1684\" data-col-size=\"sm\">Ultra-low pause times<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<hr data-start=\"1686\" data-end=\"1689\" \/>\n<h2 data-start=\"1691\" data-end=\"1732\">G1GC (Garbage First Garbage Collector)<\/h2>\n<h3 data-start=\"1734\" data-end=\"1755\">Design Philosophy<\/h3>\n<p data-start=\"1756\" data-end=\"1843\">G1GC was designed to <strong data-start=\"1777\" data-end=\"1792\">replace CMS<\/strong> with better predictability and less fragmentation.<\/p>\n<p data-start=\"1845\" data-end=\"1933\">Instead of fixed memory generations, G1GC divides the heap into <strong data-start=\"1909\" data-end=\"1932\">equal-sized regions<\/strong>.<\/p>\n<h3 data-start=\"1935\" data-end=\"1951\">Key Concepts<\/h3>\n<ul data-start=\"1952\" data-end=\"2048\">\n<li data-start=\"1952\" data-end=\"1971\">\n<p data-start=\"1954\" data-end=\"1971\">Region-based heap<\/p>\n<\/li>\n<li data-start=\"1972\" data-end=\"1992\">\n<p data-start=\"1974\" data-end=\"1992\">Concurrent marking<\/p>\n<\/li>\n<li data-start=\"1993\" data-end=\"2017\">\n<p data-start=\"1995\" data-end=\"2017\">Incremental compaction<\/p>\n<\/li>\n<li data-start=\"2018\" data-end=\"2048\">\n<p data-start=\"2020\" data-end=\"2048\">Predictable pause time goals<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"2050\" data-end=\"2068\">How G1GC Works<\/h3>\n<ol data-start=\"2069\" data-end=\"2267\">\n<li data-start=\"2069\" data-end=\"2107\">\n<p data-start=\"2072\" data-end=\"2107\">Heap divided into regions (1\u201332 MB)<\/p>\n<\/li>\n<li data-start=\"2108\" data-end=\"2157\">\n<p data-start=\"2111\" data-end=\"2157\">Regions contain Eden, Survivor, or Old objects<\/p>\n<\/li>\n<li data-start=\"2158\" data-end=\"2198\">\n<p data-start=\"2161\" data-end=\"2198\">Garbage is collected region-by-region<\/p>\n<\/li>\n<li data-start=\"2199\" data-end=\"2267\">\n<p data-start=\"2202\" data-end=\"2267\">Collector prioritizes regions with most garbage (\u201cGarbage First\u201d)<\/p>\n<\/li>\n<\/ol>\n<h3 data-start=\"2269\" data-end=\"2282\">Strengths<\/h3>\n<ul data-start=\"2283\" data-end=\"2395\">\n<li data-start=\"2283\" data-end=\"2316\">\n<p data-start=\"2285\" data-end=\"2316\">Balanced throughput and latency<\/p>\n<\/li>\n<li data-start=\"2317\" data-end=\"2369\">\n<p data-start=\"2319\" data-end=\"2369\">Predictable pause targets (<code data-start=\"2346\" data-end=\"2368\">-XX:MaxGCPauseMillis<\/code>)<\/p>\n<\/li>\n<li data-start=\"2370\" data-end=\"2395\">\n<p data-start=\"2372\" data-end=\"2395\">Default GC since Java 9<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"2397\" data-end=\"2412\">Limitations<\/h3>\n<ul data-start=\"2413\" data-end=\"2530\">\n<li data-start=\"2413\" data-end=\"2454\">\n<p data-start=\"2415\" data-end=\"2454\">Still experiences stop-the-world pauses<\/p>\n<\/li>\n<li data-start=\"2455\" data-end=\"2496\">\n<p data-start=\"2457\" data-end=\"2496\">Not ideal for ultra-low latency systems<\/p>\n<\/li>\n<li data-start=\"2497\" data-end=\"2530\">\n<p data-start=\"2499\" data-end=\"2530\">Heap size tuning still required<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"2532\" data-end=\"2550\">Best Use Cases<\/h3>\n<ul data-start=\"2551\" data-end=\"2662\">\n<li data-start=\"2551\" data-end=\"2577\">\n<p data-start=\"2553\" data-end=\"2577\">General backend services<\/p>\n<\/li>\n<li data-start=\"2578\" data-end=\"2618\">\n<p data-start=\"2580\" data-end=\"2618\">APIs with moderate latency sensitivity<\/p>\n<\/li>\n<li data-start=\"2619\" data-end=\"2662\">\n<p data-start=\"2621\" data-end=\"2662\">Applications with heap sizes up to ~100GB<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"2664\" data-end=\"2667\" \/>\n<h2 data-start=\"2669\" data-end=\"2697\">ZGC (Z Garbage Collector)<\/h2>\n<h3 data-start=\"2699\" data-end=\"2720\">Design Philosophy<\/h3>\n<p data-start=\"2721\" data-end=\"2793\">ZGC was built for <strong data-start=\"2739\" data-end=\"2767\">consistently low latency<\/strong>, regardless of heap size.<\/p>\n<p data-start=\"2795\" data-end=\"2812\">Its core promise:<\/p>\n<blockquote data-start=\"2813\" data-end=\"2875\">\n<p data-start=\"2815\" data-end=\"2875\">Pause times under <strong data-start=\"2833\" data-end=\"2842\">10 ms<\/strong>, even with multi-terabyte heaps.<\/p>\n<\/blockquote>\n<h3 data-start=\"2877\" data-end=\"2896\">Key Innovations<\/h3>\n<ul data-start=\"2897\" data-end=\"2997\">\n<li data-start=\"2897\" data-end=\"2915\">\n<p data-start=\"2899\" data-end=\"2915\">Colored pointers<\/p>\n<\/li>\n<li data-start=\"2916\" data-end=\"2931\">\n<p data-start=\"2918\" data-end=\"2931\">Load barriers<\/p>\n<\/li>\n<li data-start=\"2932\" data-end=\"2961\">\n<p data-start=\"2934\" data-end=\"2961\">Fully concurrent compaction<\/p>\n<\/li>\n<li data-start=\"2962\" data-end=\"2997\">\n<p data-start=\"2964\" data-end=\"2997\">Region-based heap (called ZPages)<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"2999\" data-end=\"3016\">How ZGC Works<\/h3>\n<ul data-start=\"3017\" data-end=\"3174\">\n<li data-start=\"3017\" data-end=\"3061\">\n<p data-start=\"3019\" data-end=\"3061\">Object relocation happens <strong data-start=\"3045\" data-end=\"3061\">concurrently<\/strong><\/p>\n<\/li>\n<li data-start=\"3062\" data-end=\"3092\">\n<p data-start=\"3064\" data-end=\"3092\">Threads are minimally paused<\/p>\n<\/li>\n<li data-start=\"3093\" data-end=\"3131\">\n<p data-start=\"3095\" data-end=\"3131\">Pointer coloring tracks object state<\/p>\n<\/li>\n<li data-start=\"3132\" data-end=\"3174\">\n<p data-start=\"3134\" data-end=\"3174\">No traditional stop-the-world compaction<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3176\" data-end=\"3189\">Strengths<\/h3>\n<ul data-start=\"3190\" data-end=\"3270\">\n<li data-start=\"3190\" data-end=\"3217\">\n<p data-start=\"3192\" data-end=\"3217\">Extremely low pause times<\/p>\n<\/li>\n<li data-start=\"3218\" data-end=\"3244\">\n<p data-start=\"3220\" data-end=\"3244\">Scales to multi-TB heaps<\/p>\n<\/li>\n<li data-start=\"3245\" data-end=\"3270\">\n<p data-start=\"3247\" data-end=\"3270\">Minimal tuning required<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3272\" data-end=\"3287\">Limitations<\/h3>\n<ul data-start=\"3288\" data-end=\"3418\">\n<li data-start=\"3288\" data-end=\"3318\">\n<p data-start=\"3290\" data-end=\"3318\">Slightly higher CPU overhead<\/p>\n<\/li>\n<li data-start=\"3319\" data-end=\"3381\">\n<p data-start=\"3321\" data-end=\"3381\">Requires newer JVMs (Java 11+ production-ready from Java 15)<\/p>\n<\/li>\n<li data-start=\"3382\" data-end=\"3418\">\n<p data-start=\"3384\" data-end=\"3418\">Less mature tooling compared to G1<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3420\" data-end=\"3438\">Best Use Cases<\/h3>\n<ul data-start=\"3439\" data-end=\"3569\">\n<li data-start=\"3439\" data-end=\"3499\">\n<p data-start=\"3441\" data-end=\"3499\">Low-latency systems (fintech, gaming, real-time analytics)<\/p>\n<\/li>\n<li data-start=\"3500\" data-end=\"3525\">\n<p data-start=\"3502\" data-end=\"3525\">Large heap applications<\/p>\n<\/li>\n<li data-start=\"3526\" data-end=\"3569\">\n<p data-start=\"3528\" data-end=\"3569\">Cloud workloads sensitive to tail latency<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"3571\" data-end=\"3574\" \/>\n<h2 data-start=\"3576\" data-end=\"3592\">Shenandoah GC<\/h2>\n<h3 data-start=\"3594\" data-end=\"3615\">Design Philosophy<\/h3>\n<p data-start=\"3616\" data-end=\"3681\">Shenandoah focuses on <strong data-start=\"3638\" data-end=\"3680\">pause-time independence from heap size<\/strong>.<\/p>\n<p data-start=\"3683\" data-end=\"3759\">Unlike ZGC, Shenandoah uses <strong data-start=\"3711\" data-end=\"3730\">brooks pointers<\/strong> instead of colored pointers.<\/p>\n<h3 data-start=\"3761\" data-end=\"3784\">Key Characteristics<\/h3>\n<ul data-start=\"3785\" data-end=\"3860\">\n<li data-start=\"3785\" data-end=\"3808\">\n<p data-start=\"3787\" data-end=\"3808\">Concurrent compaction<\/p>\n<\/li>\n<li data-start=\"3809\" data-end=\"3828\">\n<p data-start=\"3811\" data-end=\"3828\">Region-based heap<\/p>\n<\/li>\n<li data-start=\"3829\" data-end=\"3860\">\n<p data-start=\"3831\" data-end=\"3860\">Minimal stop-the-world pauses<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"3862\" data-end=\"3886\">How Shenandoah Works<\/h3>\n<ul data-start=\"3887\" data-end=\"4014\">\n<li data-start=\"3887\" data-end=\"3926\">\n<p data-start=\"3889\" data-end=\"3926\">Object relocation occurs concurrently<\/p>\n<\/li>\n<li data-start=\"3927\" data-end=\"3971\">\n<p data-start=\"3929\" data-end=\"3971\">Read barriers update references on the fly<\/p>\n<\/li>\n<li data-start=\"3972\" data-end=\"4014\">\n<p data-start=\"3974\" data-end=\"4014\">Heap fragmentation is actively prevented<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"4016\" data-end=\"4029\">Strengths<\/h3>\n<ul data-start=\"4030\" data-end=\"4130\">\n<li data-start=\"4030\" data-end=\"4055\">\n<p data-start=\"4032\" data-end=\"4055\">Predictable low latency<\/p>\n<\/li>\n<li data-start=\"4056\" data-end=\"4085\">\n<p data-start=\"4058\" data-end=\"4085\">OpenJDK and Red Hat backing<\/p>\n<\/li>\n<li data-start=\"4086\" data-end=\"4130\">\n<p data-start=\"4088\" data-end=\"4130\">Good performance under allocation pressure<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"4132\" data-end=\"4147\">Limitations<\/h3>\n<ul data-start=\"4148\" data-end=\"4253\">\n<li data-start=\"4148\" data-end=\"4176\">\n<p data-start=\"4150\" data-end=\"4176\">Slightly more CPU overhead<\/p>\n<\/li>\n<li data-start=\"4177\" data-end=\"4215\">\n<p data-start=\"4179\" data-end=\"4215\">Fewer <a href=\"https:\/\/harshad-sonawane.com\/blog\/java-memory-management-heap-gc-best\/\">JVM<\/a> diagnostics compared to G1<\/p>\n<\/li>\n<li data-start=\"4216\" data-end=\"4253\">\n<p data-start=\"4218\" data-end=\"4253\">Smaller ecosystem adoption than ZGC<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"4255\" data-end=\"4273\">Best Use Cases<\/h3>\n<ul data-start=\"4274\" data-end=\"4366\">\n<li data-start=\"4274\" data-end=\"4302\">\n<p data-start=\"4276\" data-end=\"4302\">Latency-sensitive services<\/p>\n<\/li>\n<li data-start=\"4303\" data-end=\"4325\">\n<p data-start=\"4305\" data-end=\"4325\"><a href=\"https:\/\/harshad-sonawane.com\/blog\/monitoring-java-applications-prometheus-grafana-kubernetes\/\">Kubernetes<\/a> workloads<\/p>\n<\/li>\n<li data-start=\"4326\" data-end=\"4366\">\n<p data-start=\"4328\" data-end=\"4366\">JVMs provided by Red Hat distributions<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"4368\" data-end=\"4371\" \/>\n<h2 data-start=\"4373\" data-end=\"4401\">G1GC vs ZGC vs Shenandoah<\/h2>\n<div class=\"TyagGW_tableContainer\">\n<div class=\"group TyagGW_tableWrapper flex flex-col-reverse w-fit\" tabindex=\"-1\">\n<table data-start=\"4403\" data-end=\"4739\" class=\"w-fit min-w-(--thread-content-width)\">\n<thead data-start=\"4403\" data-end=\"4440\">\n<tr data-start=\"4403\" data-end=\"4440\">\n<th data-start=\"4403\" data-end=\"4413\" data-col-size=\"sm\">Feature<\/th>\n<th data-start=\"4413\" data-end=\"4420\" data-col-size=\"sm\">G1GC<\/th>\n<th data-start=\"4420\" data-end=\"4426\" data-col-size=\"sm\">ZGC<\/th>\n<th data-start=\"4426\" data-end=\"4440\" data-col-size=\"sm\">Shenandoah<\/th>\n<\/tr>\n<\/thead>\n<tbody data-start=\"4459\" data-end=\"4739\">\n<tr data-start=\"4459\" data-end=\"4503\">\n<td data-start=\"4459\" data-end=\"4472\" data-col-size=\"sm\">Pause Time<\/td>\n<td data-col-size=\"sm\" data-start=\"4472\" data-end=\"4484\">10\u2013200 ms<\/td>\n<td data-col-size=\"sm\" data-start=\"4484\" data-end=\"4493\">&lt;10 ms<\/td>\n<td data-col-size=\"sm\" data-start=\"4493\" data-end=\"4503\">&lt;10 ms<\/td>\n<\/tr>\n<tr data-start=\"4504\" data-end=\"4561\">\n<td data-start=\"4504\" data-end=\"4524\" data-col-size=\"sm\">Heap Size Support<\/td>\n<td data-col-size=\"sm\" data-start=\"4524\" data-end=\"4539\">Medium\u2013Large<\/td>\n<td data-col-size=\"sm\" data-start=\"4539\" data-end=\"4552\">Very Large<\/td>\n<td data-col-size=\"sm\" data-start=\"4552\" data-end=\"4561\">Large<\/td>\n<\/tr>\n<tr data-start=\"4562\" data-end=\"4628\">\n<td data-start=\"4562\" data-end=\"4575\" data-col-size=\"sm\">Compaction<\/td>\n<td data-col-size=\"sm\" data-start=\"4575\" data-end=\"4589\">Incremental<\/td>\n<td data-col-size=\"sm\" data-start=\"4589\" data-end=\"4608\">Fully Concurrent<\/td>\n<td data-col-size=\"sm\" data-start=\"4608\" data-end=\"4628\">Fully Concurrent<\/td>\n<\/tr>\n<tr data-start=\"4629\" data-end=\"4669\">\n<td data-start=\"4629\" data-end=\"4644\" data-col-size=\"sm\">CPU Overhead<\/td>\n<td data-col-size=\"sm\" data-start=\"4644\" data-end=\"4650\">Low<\/td>\n<td data-col-size=\"sm\" data-start=\"4650\" data-end=\"4659\">Medium<\/td>\n<td data-col-size=\"sm\" data-start=\"4659\" data-end=\"4669\">Medium<\/td>\n<\/tr>\n<tr data-start=\"4670\" data-end=\"4708\">\n<td data-start=\"4670\" data-end=\"4681\" data-col-size=\"sm\">Maturity<\/td>\n<td data-col-size=\"sm\" data-start=\"4681\" data-end=\"4693\">Very High<\/td>\n<td data-col-size=\"sm\" data-start=\"4693\" data-end=\"4700\">High<\/td>\n<td data-col-size=\"sm\" data-start=\"4700\" data-end=\"4708\">High<\/td>\n<\/tr>\n<tr data-start=\"4709\" data-end=\"4739\">\n<td data-start=\"4709\" data-end=\"4722\" data-col-size=\"sm\">Default GC<\/td>\n<td data-col-size=\"sm\" data-start=\"4722\" data-end=\"4728\">Yes<\/td>\n<td data-col-size=\"sm\" data-start=\"4728\" data-end=\"4733\">No<\/td>\n<td data-col-size=\"sm\" data-start=\"4733\" data-end=\"4739\">No<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<hr data-start=\"4741\" data-end=\"4744\" \/>\n<h2 data-start=\"4746\" data-end=\"4770\">Choosing the Right GC<\/h2>\n<h3 data-start=\"4772\" data-end=\"4795\">Choose <strong data-start=\"4783\" data-end=\"4791\">G1GC<\/strong> if:<\/h3>\n<ul data-start=\"4796\" data-end=\"4900\">\n<li data-start=\"4796\" data-end=\"4829\">\n<p data-start=\"4798\" data-end=\"4829\">You want stability and maturity<\/p>\n<\/li>\n<li data-start=\"4830\" data-end=\"4866\">\n<p data-start=\"4832\" data-end=\"4866\">Latency under 200 ms is acceptable<\/p>\n<\/li>\n<li data-start=\"4867\" data-end=\"4900\">\n<p data-start=\"4869\" data-end=\"4900\">You prefer default JVM behavior<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"4902\" data-end=\"4924\">Choose <strong data-start=\"4913\" data-end=\"4920\">ZGC<\/strong> if:<\/h3>\n<ul data-start=\"4925\" data-end=\"5003\">\n<li data-start=\"4925\" data-end=\"4951\">\n<p data-start=\"4927\" data-end=\"4951\">Tail latency is critical<\/p>\n<\/li>\n<li data-start=\"4952\" data-end=\"4977\">\n<p data-start=\"4954\" data-end=\"4977\">You operate large heaps<\/p>\n<\/li>\n<li data-start=\"4978\" data-end=\"5003\">\n<p data-start=\"4980\" data-end=\"5003\">You want minimal tuning<\/p>\n<\/li>\n<\/ul>\n<h3 data-start=\"5005\" data-end=\"5034\">Choose <strong data-start=\"5016\" data-end=\"5030\">Shenandoah<\/strong> if:<\/h3>\n<ul data-start=\"5035\" data-end=\"5151\">\n<li data-start=\"5035\" data-end=\"5072\">\n<p data-start=\"5037\" data-end=\"5072\">You need low pauses on Red Hat JVMs<\/p>\n<\/li>\n<li data-start=\"5073\" data-end=\"5106\">\n<p data-start=\"5075\" data-end=\"5106\">You run containerized workloads<\/p>\n<\/li>\n<li data-start=\"5107\" data-end=\"5151\">\n<p data-start=\"5109\" data-end=\"5151\">You can tolerate slightly higher CPU usage<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"5153\" data-end=\"5156\" \/>\n<h2 data-start=\"5158\" data-end=\"5198\">Practical JVM Flags (Quick Reference)<\/h2>\n<h3 data-start=\"5200\" data-end=\"5208\">G1GC<\/h3>\n<div class=\"contain-inline-size rounded-2xl corner-superellipse\/1.1 relative bg-token-sidebar-surface-primary\">\n<div class=\"sticky top-[calc(--spacing(9)+var(--header-height))] @w-xl\/main:top-9\">\n<div class=\"absolute end-0 bottom-0 flex h-9 items-center pe-2\">\n<div class=\"bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs\"><\/div>\n<\/div>\n<\/div>\n<div class=\"overflow-y-auto p-4\" dir=\"ltr\"><code class=\"whitespace-pre! language-bash\"><span>-XX:+UseG1GC<br \/>\n-XX:MaxGCPauseMillis=200<br \/>\n<\/span><\/code><\/div>\n<\/div>\n<h3 data-start=\"5260\" data-end=\"5267\">ZGC<\/h3>\n<div class=\"contain-inline-size rounded-2xl corner-superellipse\/1.1 relative bg-token-sidebar-surface-primary\">\n<div class=\"sticky top-[calc(--spacing(9)+var(--header-height))] @w-xl\/main:top-9\">\n<div class=\"absolute end-0 bottom-0 flex h-9 items-center pe-2\">\n<div class=\"bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs\"><\/div>\n<\/div>\n<\/div>\n<div class=\"overflow-y-auto p-4\" dir=\"ltr\"><code class=\"whitespace-pre! language-bash\"><span>-XX:+UseZGC<br \/>\n<\/span><\/code><\/div>\n<\/div>\n<h3 data-start=\"5293\" data-end=\"5307\">Shenandoah<\/h3>\n<div class=\"contain-inline-size rounded-2xl corner-superellipse\/1.1 relative bg-token-sidebar-surface-primary\">\n<div class=\"sticky top-[calc(--spacing(9)+var(--header-height))] @w-xl\/main:top-9\">\n<div class=\"absolute end-0 bottom-0 flex h-9 items-center pe-2\">\n<div class=\"bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs\"><\/div>\n<\/div>\n<\/div>\n<div class=\"overflow-y-auto p-4\" dir=\"ltr\"><code class=\"whitespace-pre! language-bash\"><span>-XX:+UseShenandoahGC<br \/>\n<\/span><\/code><\/div>\n<\/div>\n<hr data-start=\"5342\" data-end=\"5345\" \/>\n<h2 data-start=\"5347\" data-end=\"5375\">Common GC Tuning Mistakes<\/h2>\n<ul data-start=\"5377\" data-end=\"5522\">\n<li data-start=\"5377\" data-end=\"5420\">\n<p data-start=\"5379\" data-end=\"5420\">Over-tuning before understanding workload<\/p>\n<\/li>\n<li data-start=\"5421\" data-end=\"5447\">\n<p data-start=\"5423\" data-end=\"5447\">Ignoring allocation rate<\/p>\n<\/li>\n<li data-start=\"5448\" data-end=\"5485\">\n<p data-start=\"5450\" data-end=\"5485\">Monitoring only average pause times<\/p>\n<\/li>\n<li data-start=\"5486\" data-end=\"5522\">\n<p data-start=\"5488\" data-end=\"5522\">Forgetting container memory limits<\/p>\n<\/li>\n<\/ul>\n<blockquote data-start=\"5524\" data-end=\"5558\">\n<p data-start=\"5526\" data-end=\"5558\">\u26a0\ufe0f Always profile before tuning.<\/p>\n<\/blockquote>\n<hr data-start=\"5560\" data-end=\"5563\" \/>\n<h2 data-start=\"5565\" data-end=\"5582\">Final Thoughts<\/h2>\n<p data-start=\"5584\" data-end=\"5744\">Modern Java garbage collectors are <strong data-start=\"5619\" data-end=\"5642\">engineering marvels<\/strong>. While G1GC remains a safe default, <strong data-start=\"5679\" data-end=\"5743\">ZGC and Shenandoah redefine what low-latency Java looks like<\/strong>.<\/p>\n<p data-start=\"5746\" data-end=\"5799\">Understanding their internals empowers developers to:<\/p>\n<ul data-start=\"5800\" data-end=\"5886\">\n<li data-start=\"5800\" data-end=\"5839\">\n<p data-start=\"5802\" data-end=\"5839\">Make informed architectural decisions<\/p>\n<\/li>\n<li data-start=\"5840\" data-end=\"5860\">\n<p data-start=\"5842\" data-end=\"5860\">Reduce cloud costs<\/p>\n<\/li>\n<li data-start=\"5861\" data-end=\"5886\">\n<p data-start=\"5863\" data-end=\"5886\">Improve user experience<\/p>\n<\/li>\n<\/ul>\n<p data-start=\"5888\" data-end=\"5952\">Mastering GC is no longer optional\u2014it\u2019s a competitive advantage.<\/p>\n<h2 data-start=\"6495\" data-end=\"6508\">References<\/h2>\n<ul data-start=\"6510\" data-end=\"6721\">\n<li data-start=\"6510\" data-end=\"6564\">\n<p data-start=\"6512\" data-end=\"6564\"><a data-start=\"6512\" data-end=\"6562\" rel=\"noopener\" target=\"_new\" class=\"decorated-link\" href=\"https:\/\/docs.oracle.com\/en\/java\/javase\/21\/gctuning\">https:\/\/docs.oracle.com\/en\/java\/javase\/21\/gctuning<span aria-hidden=\"true\" class=\"ms-0.5 inline-block align-middle leading-none\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" aria-hidden=\"true\" data-rtl-flip=\"\" class=\"block h-[0.75em] w-[0.75em] stroke-current stroke-[0.75]\"><use href=\"\/cdn\/assets\/sprites-core-ihvgg3b1.svg#304883\" fill=\"currentColor\"><\/use><\/svg><\/span><\/a><\/p>\n<\/li>\n<li data-start=\"6565\" data-end=\"6599\">\n<p data-start=\"6567\" data-end=\"6599\"><a data-start=\"6567\" data-end=\"6597\" rel=\"noopener\" target=\"_new\" class=\"decorated-link cursor-pointer\">https:\/\/openjdk.org\/groups\/zgc<span aria-hidden=\"true\" class=\"ms-0.5 inline-block align-middle leading-none\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" aria-hidden=\"true\" data-rtl-flip=\"\" class=\"block h-[0.75em] w-[0.75em] stroke-current stroke-[0.75]\"><use href=\"\/cdn\/assets\/sprites-core-ihvgg3b1.svg#304883\" fill=\"currentColor\"><\/use><\/svg><\/span><\/a><\/p>\n<\/li>\n<li data-start=\"6600\" data-end=\"6643\">\n<p data-start=\"6602\" data-end=\"6643\"><a data-start=\"6602\" data-end=\"6641\" rel=\"noopener\" target=\"_new\" class=\"decorated-link\" href=\"https:\/\/openjdk.org\/projects\/shenandoah\">https:\/\/openjdk.org\/projects\/shenandoah<span aria-hidden=\"true\" class=\"ms-0.5 inline-block align-middle leading-none\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" aria-hidden=\"true\" data-rtl-flip=\"\" class=\"block h-[0.75em] w-[0.75em] stroke-current stroke-[0.75]\"><use href=\"\/cdn\/assets\/sprites-core-ihvgg3b1.svg#304883\" fill=\"currentColor\"><\/use><\/svg><\/span><\/a><\/p>\n<\/li>\n<li data-start=\"6644\" data-end=\"6696\">\n<p data-start=\"6646\" data-end=\"6696\"><a data-start=\"6646\" data-end=\"6694\" rel=\"noopener\" target=\"_new\" class=\"decorated-link cursor-pointer\">https:\/\/www.baeldung.com\/java-garbage-collection<span aria-hidden=\"true\" class=\"ms-0.5 inline-block align-middle leading-none\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"20\" height=\"20\" aria-hidden=\"true\" data-rtl-flip=\"\" class=\"block h-[0.75em] w-[0.75em] stroke-current stroke-[0.75]\"><use href=\"\/cdn\/assets\/sprites-core-ihvgg3b1.svg#304883\" fill=\"currentColor\"><\/use><\/svg><\/span><\/a><\/p>\n<\/li>\n<li data-start=\"6697\" data-end=\"6721\">\n<p data-start=\"6699\" data-end=\"6721\"><a data-start=\"6699\" data-end=\"6719\" rel=\"noopener\" target=\"_new\" class=\"decorated-link\" href=\"https:\/\/inside.java\/\">https:\/\/inside.java\/<\/a><\/p>\n<\/li>\n<\/ul>\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p class=\"o-typing-delay-100ms ticss-27f7e3e9\"><o-anim-typing>&lt;> <strong>&#8220;Happy developing, one line at a time!&#8221;<\/strong> &lt;\/><\/o-anim-typing><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Memory management has always been one of Java\u2019s strongest advantages\u2014and one of its most misunderstood components. While Java developers rarely manage memory manually, the choice and tuning of the Garbage Collector (GC) can dramatically impact application latency, throughput, and scalability. With modern JVMs offering multiple advanced collectors, understanding G1GC, ZGC, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":447,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_themeisle_gutenberg_block_has_review":false,"footnotes":"","jetpack_publicize_message":"Java performance isn\u2019t just about clean code\u2014it\u2019s about understanding the JVM.\nI\u2019ve published a deep dive into G1GC, ZGC, and Shenandoah, breaking down how they work internally and when to use each one.\nIf you care about latency, scalability, or JVM tuning, this one\u2019s worth your time.\n\n#Java #JVM #GarbageCollection #PerformanceEngineering #BackendDevelopment","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[113],"tags":[329,331,334,333,335,332,330],"class_list":["post-443","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-spring-boot-aws-microservices","tag-g1gc","tag-java-gc","tag-java-memory-management","tag-jvm-performance","tag-low-latency-java","tag-shenandoah","tag-zgc"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Java Garbage Collection Algorithms<\/title>\n<meta name=\"description\" content=\"A deep technical comparison of Java garbage collectors G1GC, ZGC, and Shenandoah, explaining internals, performance trade-offs, and real-world use cases.\" \/>\n<meta name=\"robots\" content=\"index, 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