No description
  • C 96.8%
  • Assembly 0.9%
  • Rust 0.7%
  • Shell 0.6%
  • Python 0.5%
  • Other 0.3%
Find a file
William Palacek 4044574b1e drm/amdkfd: skip migration when the fault window is already in VRAM
svm_migrate_vma_to_vram() is called for windows that are already fully
resident in the target GPU's VRAM. migrate_vma_setup() raises an MMU
notifier invalidate before it can discover there is nothing to collect,
and with retry faults enabled svm_range_cpu_invalidate_pagetables()
special cases only MMU_NOTIFY_UNMAP, so MMU_NOTIFY_MIGRATE is handled by
its default arm, reaching svm_range_evict() and then
svm_range_unmap_from_gpus().

The attempt therefore drops the window's GPU mapping and then returns
having migrated nothing, so the next fault on that window is escalated
into another migration instead of being satisfied by mapping alone.

Measured on MI300X (gfx942, SPX/NPS1, xnack+) under an HMM
oversubscription workload, 96 to 97% of to-VRAM migration attempts
collected zero pages, and the driver unmapped a window roughly 35 times
for every migration that moved data.

Test whether every page of the faulting window is already resident in
this node's VRAM and return early if it is. prange->actual_loc alone is
not sufficient: since commit a546a27684 ("drm/amdkfd: Use partial
migrations/mapping for GPU/CPU page faults in SVM") migration is per
window, so a range can report actual_loc == best_loc while part of it has
been evicted back to system memory. 3.3% of attempts were in exactly that
state and did have pages to move, so the per-page test is required rather
than the scalar alone. Instrumented over 100000 attempts on an earlier
run against a different driver build, the per-page test never skipped one
that had pages to move.

The actual_loc comparison is kept alongside the per-page test because
SVM_RANGE_VRAM_DOMAIN records only that a page is in some device's VRAM,
not which device's.

With this applied the fault driven phase of that workload falls from 270
to 348 s down to 45 to 48 s, across 9 patched and 7 unpatched runs with
no overlap at either oversubscription factor tested. page_in at the end
of that phase does not fall with it: 44.5 to 48.3M pages patched against
44.1 to 49.7M unpatched at factor 1.10, and 46.2 to 48.0M against 44.1 to
45.7M at factor 1.02. Those ranges overlap at 1.10, so the claim is that
no data is stranded, not that more moves. Unmaps per productive migration
fall from about 35 to about 2. Retry fault counts do not fall in any arm,
so this is not a refault loop; what changes is how often a fault
escalates into a migration.

The scan is bounded by the migration window, one granule on the fault
path and the whole range on the prefetch path. That is the same order as
the migrate_vma_setup() walk it avoids, and it returns at the first page
that is not resident, so the worst case is one extra pass over a range
that then migrates normally.

Signed-off-by: William Palacek <William.Palacek@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
History 2026-09-02 15:16:56 -04:00
arch - Add a proper kernel cmdline option to control the TLB invalidation method on 2026-08-16 10:28:31 -07:00
block block: stop the timeout timer when releasing a never added disk 2026-07-29 05:23:20 -06:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto This push contains the following changes: 2026-08-10 08:36:22 -07:00
Documentation Merge tag 'drm-msm-next-2026-08-01' of https://gitlab.freedesktop.org/drm/msm into drm-next 2026-08-24 11:21:12 +10:00
drivers drm/amdkfd: skip migration when the fault window is already in VRAM 2026-09-02 15:16:56 -04:00
fs A handful of tiny fixes, with the main ones being a follow-up for 2026-08-14 10:18:06 -07:00
include drm/edid: parse HDMI 2.1 gaming (ALLM/VRR) capabilities from HF-VSDB 2026-09-02 14:53:45 -04:00
init rust: allow suspicious_runtime_symbol_definitions lint for Rust >= 1.98 2026-06-29 13:02:15 +02:00
io_uring io_uring/rsrc: reject overflowing regvec bvec byte counts 2026-08-12 19:53:35 -06:00
ipc kernel-7.2-rc1.misc 2026-06-15 03:05:50 +05:30
kernel Linux 7.2 2026-08-20 10:58:44 +10:00
lib Linux 7.2 2026-08-20 10:58:44 +10:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm 17 hotfixes. 15 are cc:stable. 16 are for MM. 2026-08-06 20:29:38 -07:00
net A handful of tiny fixes, with the main ones being a follow-up for 2026-08-14 10:18:06 -07:00
rust Linux 7.2 2026-08-20 10:58:44 +10:00
samples Linux 7.2 2026-08-20 10:58:44 +10:00
scripts kbuild: rpm-pkg: Preserve BTF sections in kernel modules during debuginfo stripping 2026-07-29 16:21:42 -07:00
security selinux/stable-7.2 PR 20260805 2026-08-05 13:40:11 -07:00
sound ASoC: Fixes for v7.2 2026-08-13 15:32:36 +02:00
tools vfs-7.2-rc8.fixes 2026-08-14 07:58:01 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt KVM/arm64 fixes for 7.2, take #2 2026-07-15 12:13:30 +02:00
.clang-format drm/bridge: rename drm_for_each_bridge_in_chain_scoped() to drm_for_each_bridge_in_chain() 2026-07-14 17:55:51 +02:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore SPDX patches for 7.2-rc1 2026-06-22 12:06:22 -07:00
.mailmap Linux 7.2 2026-08-20 10:58:44 +10:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Add Wolfram Sang 2026-07-14 16:34:04 +02:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Linux 7.2 2026-08-20 10:58:44 +10:00
Makefile Linux 7.2 2026-08-16 14:32:26 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst