Train your team

KRN-221 · Linux Kernel Core

Allocators: Buddy, Slab, vmalloc

How the kernel allocates memory at every scale, and how allocator behaviour surfaces as fragmentation and latency.

Advanced 3 days in person6 half-days online Max 14 in person

Who this course is for

Kernel and driver developers who allocate memory inside the kernel and need to choose the right allocator, debug fragmentation, and read allocator state without guessing.

Prerequisites

KRN-220 or solid virtual-memory backgroundSolid CAbility to build and load test modules

Course outline

Day 1 — The buddy allocator

  • Zones, watermarks and migration types
  • Order-N allocation and why high orders fail
  • Reading /proc/buddyinfo, /proc/zoneinfo and /proc/pagetypeinfo
  • Fragmentation mechanics and what compaction can and cannot fix
  • Observing allocation latency under fragmentation

Day 2 — SLUB

  • Caches, slabs and per-CPU freelists
  • kmalloc size classes and what a kmalloc really costs
  • kmem_cache_create: when a private cache is worth it
  • /proc/slabinfo and slabtop as diagnostic tools
  • slub_debug: poisoning, red zones and tracking

Day 3 — Choosing correctly and debugging

  • kmalloc vs vmalloc vs alloc_pages: the decision rules
  • GFP flags, allocation contexts and atomic allocation
  • vmalloc space and vmap areas
  • Debugging allocator problems: leaks, corruption signatures, fragmentation reports
  • Capstone workshop

Hands-on labs

Labs follow the academy model — 35% principles, 20% guided investigation, 45% engineering studio. Every claim you make in a lab is backed by a trace, a counter or a measurement you captured yourself. How we teach

  1. Lab: drive the buddy allocator into fragmentation and read the result in /proc/buddyinfo and /proc/pagetypeinfo
  2. Lab: inspect SLUB state with slabinfo and slabtop and correlate caches with module behaviour
  3. Lab: use slub_debug poisoning to catch a use-after-free in a test module
  4. Lab: allocate the wrong way on purpose — high-order kmalloc under pressure, vmalloc in atomic context — and observe the failure modes
  5. Lab: trigger compaction and measure allocation latency before and after

Capstone project

Diagnose and fix an allocator pathology in a prepared kernel scenario: determine whether the failure is fragmentation, cache growth or a leak, prove it with buddyinfo and slabinfo evidence, apply the correct fix — GFP choice, cache design or allocation order — and show the numbers recovering under the same load.

What you leave with

  • The kmalloc/vmalloc/alloc_pages decision rules
  • GFP flag discipline for every allocation context
  • Fluent reading of buddyinfo, pagetypeinfo and slabinfo
  • slub_debug and compaction debugging practice

How it runs

Every course follows the same model: 35% principles, 20% guided investigation, 45% engineering studio. You leave with working code, raw measurements and an evidence-based report — not a certificate of attendance. Read the methodology or see a full sample lesson.

Material is adapted to your kernel version, hardware and workload before a private delivery. For public cohorts, the environment is provided and configured.

Questions

Who is this course for?

Kernel and driver developers who allocate memory inside the kernel and need to choose the right allocator, debug fragmentation, and read allocator state without guessing. It sits at advanced level within the Linux Kernel Core track.

What do I need to know already?

Specific prerequisites for this course: KRN-220 or solid virtual-memory background; Solid C; Ability to build and load test modules. We confirm levels before the cohort starts and adapt if a group is stronger or weaker than expected.

Can this run privately for my team?

Yes. Any course runs on-site at your offices anywhere, or live online for a distributed team, with labs adapted to your hardware and codebase.

What is the difference between in-person and online?

In person is 3 full days with hardware on your desk, capped at 14. Online is 6 half-day sessions across about two weeks so you can keep working, capped at 20, with remote lab access.

Do you invoice companies?

Yes. Purchase orders are accepted and invoicing is available in USD, EUR, GBP, SAR and CAD.

Upcoming dates

DatesWhereSeatsEarly birdRegular
22 Nov – 24 Nov 20263 full days RiyadhIn person · KAFD Conference Centre 6 of 14 SAR 8,100until 23 OctSAR 9,000
29 Nov – 1 Dec 20263 full days Kuwait CityIn person · Al Hamra Tower 11 of 14 KWD 670until 30 OctKWD 740
29 Nov – 1 Dec 20263 full days MuscatIn person · Knowledge Oasis Muscat 6 of 14 OMR 830until 30 OctOMR 920
6 Dec – 13 Dec 20266 half-days Gulf bandLive online · 09:00–13:00 GMT+3 14 of 20 US$1,580until 6 NovUS$1,750
7 Dec – 9 Dec 20263 full days OttawaIn person · Kanata North Tech Park 11 of 14 CAD 2,930until 7 NovCAD 3,260
14 Dec – 16 Dec 20263 full days TorontoIn person · MaRS Discovery District 6 of 14 CAD 2,930until 14 NovCAD 3,260
14 Dec – 16 Dec 20263 full days LondonIn person · Shoreditch Works 11 of 14 GBP 1,680until 14 NovGBP 1,870
14 Dec – 21 Dec 20266 half-days Europe bandLive online · 09:00–13:00 CET 3 of 20 US$1,580until 14 NovUS$1,750
14 Dec – 21 Dec 20266 half-days Americas bandLive online · 13:00–17:00 ET 8 of 20 US$1,580until 14 NovUS$1,750
21 Dec – 23 Dec 20263 full days BerlinIn person · Factory Görlitzer Park 6 of 14 EUR 1,990until 21 NovEUR 2,210

Dates shown for the next few months. If nothing fits, tell us where and when — cohorts are added on demand, and private delivery can be scheduled any week.

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