--- title: Internals for Interns | daily.dev description: A deep dive into Go's memory allocator internals. Covers how the runtime avoids frequent OS syscalls by requesting 64MB arenas upfront, subdividing them into... canonical: https://daily.dev/posts/internals-for-interns-fg0xibngw twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Internals for Interns | daily.dev og:description: A deep dive into Go's memory allocator internals. Covers how the runtime avoids frequent OS syscalls by requesting 64MB arenas upfront, subdividing them into... og:url: https://daily.dev/posts/internals-for-interns-fg0xibngw og:image: https://api.daily.dev/og/posts/fG0XIbngw.png og:image:alt: Internals for Interns 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. # Internals for Interns **[Hacker News](https://daily.dev/sources/hn)** · 22 min read · 0 upvotes · 0 comments ## Summary A deep dive into Go's memory allocator internals. Covers how the runtime avoids frequent OS syscalls by requesting 64MB arenas upfront, subdividing them into 8KB pages and then into spans holding fixed-size slots. Explains the 68 size classes (8B–32KB), the scan/noscan distinction yielding 136 span classes, and the tiny allocator for sub-16-byte pointer-free objects. Details the three-level hierarchy (mcache → mcentral → mheap) that eliminates lock contention for most allocations. Also covers GC integration via dual bitmaps (allocBits and gcmarkBits), lazy sweeping, and the background scavenger that returns unused pages to the OS via MADV_DONTNEED. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Internals for Interns](https://daily.dev/posts/internals-for-interns-b48rbnp0g) · Hacker News · 0 upvotes · 0 comments --- Tags: [#golang](https://daily.dev/tags/golang) [View this post on daily.dev](https://daily.dev/posts/internals-for-interns-fg0xibngw) ```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":"Internals for Interns","url":"https://daily.dev/posts/internals-for-interns-fg0xibngw","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/internals-for-interns-fg0xibngw"},"datePublished":"2026-02-27T11:29:18.777Z","dateModified":"2026-02-27T11:29:41.062Z","description":"A deep dive into Go's memory allocator internals. Covers how the runtime avoids frequent OS syscalls by requesting 64MB arenas upfront, subdividing them into...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/25c66f0059447946c2519c3d920afb74?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/25c66f0059447946c2519c3d920afb74?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Hacker News","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":"Hacker News","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/hn","url":"https://daily.dev/sources/hn"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/internals-for-interns-fg0xibngw","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"golang","timeRequired":"PT22M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Hacker News","item":"https://daily.dev/sources/hn"},{"@type":"ListItem","position":3,"name":"Internals for Interns"}]} ```