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Pull documentation updates from Jonathan Corbet:
"Things have calmed down a bit on the docs front, with no earthshaking
changes this time around:
- Ongoing work on the Japanese and Portuguese translations
- Better integration of the MAINTAINERS file into the rendered
documents, including a search interface
- A seemingly infinite supply of fixes for typos, minor grammatical
issues, and related problems that LLMs find with abandon"
* tag 'docs-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/docs/linux: (93 commits)
docs: pt_BR: Translate 3.Early-stage.rst into Portuguese
docs: pt_BR: update "Purpose of Defconfigs" section in maintainer-soc.rst
Documentation: bug-hunting.rst: fix grammar
docs/ja_JP: translate submitting-patches.rst (interleaved-replies)
docs: Fix minor grammatical error
docs/{it_it,sp_SP,zh_CN,zh_TW}: update references to removed CONFIG_DEBUG_SLAB
Documentation: process: fix brackets
Documentation: arch: fix brackets
docs/dyndbg: explain flags parse 1st
docs/dyndbg: update examples \012 to \n
docs: kernel-parameters: Fix stale sticore file paths
docs: real-time: Fix duplicated sched(7) text
docs: kgdb: Fix stale source file paths
docs: sonypi: Fix stale header file path
docs: kernel-parameters: Remove sa1100ir IrDA parameter
iommu: Documentation: rearrange, update kernel-parameters
docs: md: fix grammar in speed_limit description
docs: changes.rst: restore pahole 1.26 minimum (regressed by sort)
Documentation: Fix syntax of kmalloc_objs example in coding style doc
docs: pt_BR: update maintainer-handbooks
...
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procfs has a number of mounting restrictions that are not documented
anywhere.
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://patch.msgid.link/e7cb804df3c1759ee17cf9df1dc4c211d63d7a5f.1777278334.git.legion@kernel.org
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Fix missing "from" in "prevent <pid> being reused" and
add spacing in vm_area_struct range notation for readability.
No functional changes.
Signed-off-by: Myro Demma <myro@myromyro.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260428133001.11384-1-myro@myromyro.com>
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Commit e24ccaaf7ec4 ("block: remove last remaining traces of IDE
documentation") removed the IDE section but left its table of
contents entry behind.
Fix the stale entry and renumber the following sections.
Fixes: e24ccaaf7ec4 ("block: remove last remaining traces of IDE documentation")
Signed-off-by: Baolin Liu <liubaolin@kylinos.cn>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260424090654.19229-1-liubaolin12138@163.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull more MM updates from Andrew Morton:
- "Eliminate Dying Memory Cgroup" (Qi Zheng and Muchun Song)
Address the longstanding "dying memcg problem". A situation wherein a
no-longer-used memory control group will hang around for an extended
period pointlessly consuming memory
- "fix unexpected type conversions and potential overflows" (Qi Zheng)
Fix a couple of potential 32-bit/64-bit issues which were identified
during review of the "Eliminate Dying Memory Cgroup" series
- "kho: history: track previous kernel version and kexec boot count"
(Breno Leitao)
Use Kexec Handover (KHO) to pass the previous kernel's version string
and the number of kexec reboots since the last cold boot to the next
kernel, and print it at boot time
- "liveupdate: prevent double preservation" (Pasha Tatashin)
Teach LUO to avoid managing the same file across different active
sessions
- "liveupdate: Fix module unloading and unregister API" (Pasha
Tatashin)
Address an issue with how LUO handles module reference counting and
unregistration during module unloading
- "zswap pool per-CPU acomp_ctx simplifications" (Kanchana Sridhar)
Simplify and clean up the zswap crypto compression handling and
improve the lifecycle management of zswap pool's per-CPU acomp_ctx
resources
- "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race"
(SeongJae Park)
Address unlikely but possible leaks and deadlocks in damon_call() and
damon_walk()
- "mm/damon/core: validate damos_quota_goal->nid" (SeongJae Park)
Fix a couple of root-only wild pointer dereferences
- "Docs/admin-guide/mm/damon: warn commit_inputs vs other params race"
(SeongJae Park)
Update the DAMON documentation to warn operators about potential
races which can occur if the commit_inputs parameter is altered at
the wrong time
- "Minor hmm_test fixes and cleanups" (Alistair Popple)
Bugfixes and a cleanup for the HMM kernel selftests
- "Modify memfd_luo code" (Chenghao Duan)
Cleanups, simplifications and speedups to the memfd_lou code
- "mm, kvm: allow uffd support in guest_memfd" (Mike Rapoport)
Support for userfaultfd in guest_memfd
- "selftests/mm: skip several tests when thp is not available" (Chunyu
Hu)
Fix several issues in the selftests code which were causing breakage
when the tests were run on CONFIG_THP=n kernels
- "mm/mprotect: micro-optimization work" (Pedro Falcato)
A couple of nice speedups for mprotect()
- "MAINTAINERS: update KHO and LIVE UPDATE entries" (Pratyush Yadav)
Document upcoming changes in the maintenance of KHO, LUO, memfd_luo,
kexec, crash, kdump and probably other kexec-based things - they are
being moved out of mm.git and into a new git tree
* tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (121 commits)
MAINTAINERS: add page cache reviewer
mm/vmscan: avoid false-positive -Wuninitialized warning
MAINTAINERS: update Dave's kdump reviewer email address
MAINTAINERS: drop include/linux/liveupdate from LIVE UPDATE
MAINTAINERS: drop include/linux/kho/abi/ from KHO
MAINTAINERS: update KHO and LIVE UPDATE maintainers
MAINTAINERS: update kexec/kdump maintainers entries
mm/migrate_device: remove dead migration entry check in migrate_vma_collect_huge_pmd()
selftests: mm: skip charge_reserved_hugetlb without killall
userfaultfd: allow registration of ranges below mmap_min_addr
mm/vmstat: fix vmstat_shepherd double-scheduling vmstat_update
mm/hugetlb: fix early boot crash on parameters without '=' separator
zram: reject unrecognized type= values in recompress_store()
docs: proc: document ProtectionKey in smaps
mm/mprotect: special-case small folios when applying permissions
mm/mprotect: move softleaf code out of the main function
mm: remove '!root_reclaim' checking in should_abort_scan()
mm/sparse: fix comment for section map alignment
mm/page_io: use sio->len for PSWPIN accounting in sio_read_complete()
selftests/mm: transhuge_stress: skip the test when thp not available
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The ProtectionKey entry was added in v4.9; back then it was x86-specific,
but it now lives in generic code and applies to all architectures
supporting pkeys (currently x86, power, arm64).
Time to document it: add a paragraph to proc.rst about the ProtectionKey
entry.
[akpm@linux-foundation.org: s/system/hardware/, per review discussion]
[akpm@linux-foundation.org: s/hardware/CPU/]
Link: https://lore.kernel.org/20260407125133.564182-1-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Reported-by: Yury Khrustalev <yury.khrustalev@arm.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Pull drm updates from Dave Airlie:
"Highlights:
- new DRM RAS infrastructure using netlink
- amdgpu: enable DC on CIK APUs, and more IP enablement, and more
user queue work
- xe: purgeable BO support, and new hw enablement
- dma-buf : add revocable operations
Full summary:
mm:
- two-pass MMU interval notifiers
- add gpu active/reclaim per-node stat counters
math:
- provide __KERNEL_DIV_ROUND_CLOSEST() in UAPI
- implement DIV_ROUND_CLOSEST() with __KERNEL_DIV_ROUND_CLOSEST()
rust:
- shared tag with driver-core: register macro and io infra
- core: rework DMA coherent API
- core: add interop::list to interop with C linked lists
- core: add more num::Bounded operations
- core: enable generic_arg_infer and add EMSGSIZE
- workqueue: add ARef<T> support for work and delayed work
- add GPU buddy allocator abstraction
- add DRM shmem GEM helper abstraction
- allow drm:::Device to dispatch work and delayed work items
to driver private data
- add dma_resv_lock helper and raw accessors
core:
- introduce DRM RAS infrastructure over netlink
- add connector panel_type property
- fourcc: add ARM interleaved 64k modifier
- colorop: add destroy helper
- suballoc: split into alloc and init helpers
- mode: provide DRM_ARGB_GET*() macros for reading color components
edid:
- provide drm_output_color_Format
dma-buf:
- provide revoke mechanism for shared buffers
- rename move_notify to invalidate_mappings
- always enable move_notify
- protect dma_fence_ops with RCU and improve locking
- clean pages with helpers
atomic:
- allocate drm_private_state via callback
- helper: use system_percpu_wq
buddy:
- make buddy allocator available to gpu level
- add kernel-doc for buddy allocator
- improve aligned allocation
ttm:
- fix fence signalling
- improve tests and docs
- improve handling of gfp_retry_mayfail
- use per-node stat counters to track memory allocations
- port pool to use list_lru
- drop NUMA specific pools
- make pool shrinker numa aware
- track allocated pages per numa node
coreboot:
- cleanup coreboot framebuffer support
sched:
- fix race condition in drm_sched_fini
pagemap:
- enable THP support
- pass pagemap_addr by reference
gem-shmem:
- Track page accessed/dirty status across mmap/vmap
gpusvm:
- reenable device to device migration
- fix unbalanced unclock
bridge:
- anx7625: Support USB-C plus DT bindings
- connector: Fix EDID detection
- dw-hdmi-qp: Support Vendor-Specfic and SDP Infoframes; improve
others
- fsl-ldb: Fix visual artifacts plus related DT property
'enable-termination-resistor'
- imx8qxp-pixel-link: Improve bridge reference handling
- lt9611: Support Port-B-only input plus DT bindings
- tda998x: Support DRM_BRIDGE_ATTACH_NO_CONNECTOR; Clean up
- Support TH1520 HDMI plus DT bindings
- waveshare-dsi: Fix register and attach; Support 1..4 DSI lanes plus
DT bindings
- anx7625: Fix USB Type-C handling
- cdns-mhdp8546-core: Handle HDCP state in bridge atomic_check
- Support Lontium LT8713SX DP MST bridge plus DT bindings
- analogix_dp: Use DP helpers for link training
panel:
- panel-jdi-lt070me05000: Use mipi-dsi multi functions
- panel-edp: Support Add AUO B116XAT04.1 (HW: 1A); Support CMN
N116BCL-EAK (C2); Support FriendlyELEC plus DT changes
- panel-edp: Fix timings for BOE NV140WUM-N64
- ilitek-ili9882t: Allow GPIO calls to sleep
- jadard: Support TAIGUAN XTI05101-01A
- lxd: Support LXD M9189A plus DT bindings
- mantix: Fix pixel clock; Clean up
- motorola: Support Motorola Atrix 4G and Droid X2 plus DT bindings
- novatek: Support Novatek/Tianma NT37700F plus DT bindings
- simple: Support EDT ET057023UDBA plus DT bindings; Support Powertip
PH800480T032-ZHC19 plus DT bindings; Support Waveshare 13.3"
- novatek-nt36672a: Use mipi_dsi_*_multi() functions
- panel-edp: Support BOE NV153WUM-N42, CMN N153JCA-ELK, CSW
MNF307QS3-2
- support Himax HX83121A plus DT bindings
- support JuTouch JT070TM041 plus DT bindings
- support Samsung S6E8FC0 plus DT bindings
- himax-hx83102c: support Samsung S6E8FC0 plus DT bindings; support
backlight
- ili9806e: support Rocktech RK050HR345-CT106A plus DT bindings
- simple: support Tianma TM050RDH03 plus DT bindings
amdgpu:
- enable DC by default on CIK APUs
- userq fence ioctl param size fixes
- set panel_type to OLED for eDP
- refactor DC i2c code
- FAMS2 update
- rework ttm handling to allow multiple engines
- DC DCE 6.x cleanup
- DC support for NUTMEG/TRAVIS DP bridge
- DCN 4.2 support
- GC12 idle power fix for compute
- use struct drm_edid in non-DC code
- enable NV12/P010 support on primary planes
- support newer IP discovery tables
- VCN/JPEG 5.0.2 support
- GC/MES 12.1 updates
- USERQ fixes
- add DC idle state manager
- eDP DSC seamless boot
amdkfd:
- GC 12.1 updates
- non 4K page fixes
xe:
- basic Xe3p_LPG and NVL-P enabling patches
- allow VM_BIND decompress support
- add purgeable buffer object support
- add xe_vm_get_property_ioctl
- restrict multi-lrc to VCS/VECS engines
- allow disabling VM overcommit in fault mode
- dGPU memory optimizations
- Workaround cleanups and simplification
- Allow VFs VRAM quote changes using sysfs
- convert GT stats to per-cpu counters
- pagefault refactors
- enable multi-queue on xe3p_xpc
- disable DCC on PTL
- make MMIO communication more robust
- disable D3Cold for BMG on specific platforms
- vfio: improve FLR sync for Xe VFIO
i915/display:
- C10/C20/LT PHY PLL divider verification
- use trans push mechanism to generate PSR frame change on LNL+
- refactor DP DSC slice config
- VGA decode refactoring
- refactor DPT, gen2-4 overlay, masked field register macro helpers
- refactor stolen memory allocation decisions
- prepare for UHBR DP tunnels
- refactor LT PHY PLL to use DPLL framework
- implement register polling/waiting in display code
- add shared stepping header between i915 and display
i915:
- fix potential overflow of shmem scatterlist length
nouveau:
- provide Z cull info to userspace
- initial GA100 support
- shutdown on PCI device shutdown
nova-core:
- harden GSP command queue
- add support for large RPCs
- simplify GSP sequencer and message handling
- refactor falcon firmware handling
- convert to new register macro
- conver to new DMA coherent API
- use checked arithmetic
- add debugfs support for gsp-rm log buffers
- fix aux device registration for multi-GPU
msm:
- CI:
- Uprev mesa
- Restore CI jobs for Qualcomm APQ8016 and APQ8096 devices
- Core:
- Switched to of_get_available_child_by_name()
- DPU:
- Fixes for DSC panels
- Fixed brownout because of the frequency / OPP mismatch
- Quad pipe preparation (not enabled yet)
- Switched to virtual planes by default
- Dropped VBIF_NRT support
- Added support for Eliza platform
- Reworked alpha handling
- Switched to correct CWB definitions on Eliza
- Dropped dummy INTF_0 on MSM8953
- Corrected INTFs related to DP-MST
- DP:
- Removed debug prints looking into PHY internals
- DSI:
- Fixes for DSC panels
- RGB101010 support
- Support for SC8280XP
- Moved PHY bindings from display/ to phy/
- GPU:
- Preemption support for x2-85 and a840
- IFPC support for a840
- SKU detection support for x2-85 and a840
- Expose AQE support (VK ray-pipeline)
- Avoid locking in VM_BIND fence signaling path
- Fix to avoid reclaim in GPU snapshot path
- Disallow foreign mapping of _NO_SHARE BOs
- HDMI:
- Fixed infoframes programming
- MDP5:
- Dropped support for MSM8974v1
- Dropped now unused code for MSM8974 v1 and SDM660 / MSM8998
panthor:
- add tracepoints for power and IRQs
- fix fence handling
- extend timestamp query with flags
- support various sources for timestamp queries
tyr:
- fix names and model/versions
rockchip:
- vop2: use drm logging function
- rk3576 displayport support
- support CRTC background color
atmel-hlcdc:
- support sana5d65 LCD controller
tilcdc:
- use DT bindings schema
- use managed DRM interfaces
- support DRM_BRIDGE_ATTACH_NO_CONNECTOR
verisilicon:
- support DC8200 + DT bindings
virtgpu:
- support PRIME import with 3D enabled
komeda:
- fix integer overflow in AFBC checks
mcde:
- improve bridge handling
gma500:
- use drm client buffer for fbdev framebuffer
amdxdna:
- add sensors ioctls
- provide NPU power estimate
- support column utilization sensor
- allow forcing DMA through IOMMU IOVA
- support per-BO mem usage queries
- refactor GEM implementation
ivpu:
- update boot API to v3.29.4
- limit per-user number of doorbells/contexts
- perform engine reset on TDR error
loongson:
- replace custom code with drm_gem_ttm_dumb_map_offset()
imx:
- support planes behind the primary plane
- fix bus-format selection
vkms:
- support CRTC background color
v3d:
- improve handling of struct v3d_stats
komeda:
- support Arm China Linlon D6 plus DT bindings
imagination:
- improve power-off sequence
- support context-reset notification from firmware
mediatek:
- mtk_dsi: enable hs clock during pre-enable
- Remove all conflicting aperture devices during probe
- Add support for mt8167 display blocks"
* tag 'drm-next-2026-04-15' of https://gitlab.freedesktop.org/drm/kernel: (1735 commits)
drm/ttm/tests: Remove checks from ttm_pool_free_no_dma_alloc
drm/ttm/tests: fix lru_count ASSERT
drm/vram: remove DRM_VRAM_MM_FILE_OPERATIONS from docs
drm/fb-helper: Fix a locking bug in an error path
dma-fence: correct kernel-doc function parameter @flags
ttm/pool: track allocated_pages per numa node.
ttm/pool: make pool shrinker NUMA aware (v2)
ttm/pool: drop numa specific pools
ttm/pool: port to list_lru. (v2)
drm/ttm: use gpu mm stats to track gpu memory allocations. (v4)
mm: add gpu active/reclaim per-node stat counters (v2)
gpu: nova-core: fix missing colon in SEC2 boot debug message
gpu: nova-core: vbios: use from_le_bytes() for PCI ROM header parsing
gpu: nova-core: bitfield: fix broken Default implementation
gpu: nova-core: falcon: pad firmware DMA object size to required block alignment
gpu: nova-core: gsp: fix undefined behavior in command queue code
drm/shmem_helper: Make sure PMD entries get the writeable upgrade
accel/ivpu: Trigger recovery on TDR with OS scheduling
drm/msm: Use of_get_available_child_by_name()
dt-bindings: display/msm: move DSI PHY bindings to phy/ subdir
...
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While discussing memcg intergration with gpu memory allocations,
it was pointed out that there was no numa/system counters for
GPU memory allocations.
With more integrated memory GPU server systems turning up, and
more requirements for memory tracking it seems we should start
closing the gap.
Add two counters to track GPU per-node system memory allocations.
The first is currently allocated to GPU objects, and the second
is for memory that is stored in GPU page pools that can be reclaimed,
by the shrinker.
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
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Commit 2e5449f4f21a ("profiling: Remove create_prof_cpu_mask().") said that
no one would create /proc/irq/prof_cpu_mask since commit 1f44a225777e
("s390: convert interrupt handling to use generic hardirq", 2013). Remove
the outdated description.
While at it, fix another minor typo (s/DMS/DMA/).
Signed-off-by: Zenghui Yu (Huawei) <zenghui.yu@linux.dev>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260311070940.94838-1-zenghui.yu@linux.dev>
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There was recently some confusion around THPs and the interaction with
KernelPageSize / MMUPageSize. Historically, these entries always
correspond to the smallest size we could encounter, not any current
usage of transparent huge pages or larger sizes used by the MMU.
Ever since we added THP support many, many years ago, these entries
would keep reporting the smallest (fallback) granularity in a VMA.
For this reason, they default to PAGE_SIZE for all VMAs except for
VMAs where we have the guarantee that the system and the MMU will
always use larger page sizes. hugetlb, for example, exposes a custom
vm_ops->pagesize callback to handle that. Similarly, dax/device
exposes a custom vm_ops->pagesize callback and provides similar
guarantees.
Let's clarify the historical meaning of KernelPageSize / MMUPageSize,
and point at "AnonHugePages", "ShmemPmdMapped" and "FilePmdMapped"
regarding PMD entries.
While at it, document "FilePmdMapped", clarify what the "AnonHugePages"
and "ShmemPmdMapped" entries really mean, and make it clear that there
are no other entries for other THP/folio sizes or mappings.
Also drop the duplicate "KernelPageSize" and "MMUPageSize" entries in
the example.
Link: https://lore.kernel.org/all/20260225232708.87833-1-ak@linux.intel.com/
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260306081916.38872-1-david@kernel.org>
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The entry in proc.rst for 3.14 is missing the closing ">" of the "pid"
field for the ksm_stat file. Add this for both the table of contents and
the actual header for the "ksm_stat" file.
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Böhler <witcher@wiredspace.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260131-ksm_stat-v2-1-a8fea12d604e@wiredspace.de>
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Patch series "introduce VM_MAYBE_GUARD and make it sticky", v4.
Currently, guard regions are not visible to users except through
/proc/$pid/pagemap, with no explicit visibility at the VMA level.
This makes the feature less useful, as it isn't entirely apparent which
VMAs may have these entries present, especially when performing actions
which walk through memory regions such as those performed by CRIU.
This series addresses this issue by introducing the VM_MAYBE_GUARD flag
which fulfils this role, updating the smaps logic to display an entry for
these.
The semantics of this flag are that a guard region MAY be present if set
(we cannot be sure, as we can't efficiently track whether an
MADV_GUARD_REMOVE finally removes all the guard regions in a VMA) - but if
not set the VMA definitely does NOT have any guard regions present.
It's problematic to establish this flag without further action, because
that means that VMAs with guard regions in them become non-mergeable with
adjacent VMAs for no especially good reason.
To work around this, this series also introduces the concept of 'sticky'
VMA flags - that is flags which:
a. if set in one VMA and not in another still permit those VMAs to be
merged (if otherwise compatible).
b. When they are merged, the resultant VMA must have the flag set.
The VMA logic is updated to propagate these flags correctly.
Additionally, VM_MAYBE_GUARD being an explicit VMA flag allows us to solve
an issue with file-backed guard regions - previously these established an
anon_vma object for file-backed mappings solely to have vma_needs_copy()
correctly propagate guard region mappings to child processes.
We introduce a new flag alias VM_COPY_ON_FORK (which currently only
specifies VM_MAYBE_GUARD) and update vma_needs_copy() to check explicitly
for this flag and to copy page tables if it is present, which resolves
this issue.
Additionally, we add the ability for allow-listed VMA flags to be
atomically writable with only mmap/VMA read locks held.
The only flag we allow so far is VM_MAYBE_GUARD, which we carefully ensure
does not cause any races by being allowed to do so.
This allows us to maintain guard region installation as a read-locked
operation and not endure the overhead of obtaining a write lock here.
Finally we introduce extensive VMA userland tests to assert that the
sticky VMA logic behaves correctly as well as guard region self tests to
assert that smaps visibility is correctly implemented.
This patch (of 9):
Currently, if a user needs to determine if guard regions are present in a
range, they have to scan all VMAs (or have knowledge of which ones might
have guard regions).
Since commit 8e2f2aeb8b48 ("fs/proc/task_mmu: add guard region bit to
pagemap") and the related commit a516403787e0 ("fs/proc: extend the
PAGEMAP_SCAN ioctl to report guard regions"), users can use either
/proc/$pid/pagemap or the PAGEMAP_SCAN functionality to perform this
operation at a virtual address level.
This is not ideal, and it gives no visibility at a /proc/$pid/smaps level
that guard regions exist in ranges.
This patch remedies the situation by establishing a new VMA flag,
VM_MAYBE_GUARD, to indicate that a VMA may contain guard regions (it is
uncertain because we cannot reasonably determine whether a
MADV_GUARD_REMOVE call has removed all of the guard regions in a VMA, and
additionally VMAs may change across merge/split).
We utilise 0x800 for this flag which makes it available to 32-bit
architectures also, a flag that was previously used by VM_DENYWRITE, which
was removed in commit 8d0920bde5eb ("mm: remove VM_DENYWRITE") and hasn't
bee reused yet.
We also update the smaps logic and documentation to identify these VMAs.
Another major use of this functionality is that we can use it to identify
that we ought to copy page tables on fork.
We do not actually implement usage of this flag in mm/madvise.c yet as we
need to allow some VMA flags to be applied atomically under mmap/VMA read
lock in order to avoid the need to acquire a write lock for this purpose.
Link: https://lkml.kernel.org/r/cover.1763460113.git.lorenzo.stoakes@oracle.com
Link: https://lkml.kernel.org/r/cf8ef821eba29b6c5b5e138fffe95d6dcabdedb9.1763460113.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Andrei Vagin <avagin@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Pull VFIO updates from Alex Williamson:
- Use fdinfo to expose the sysfs path of a device represented by a vfio
device file (Alex Mastro)
- Mark vfio-fsl-mc, vfio-amba, and the reset functions for
vfio-platform for removal as these are either orphaned or believed to
be unused (Alex Williamson)
- Add reviewers for vfio-platform to save it from also being marked for
removal (Mostafa Saleh, Pranjal Shrivastava)
- VFIO selftests, including basic sanity testing and minimal userspace
drivers for testing against real hardware. This is also expected to
provide integration with KVM selftests for KVM-VFIO interfaces (David
Matlack, Josh Hilke)
- Fix drivers/cdx and vfio/cdx to build without CONFIG_GENERIC_MSI_IRQ
(Nipun Gupta)
- Fix reference leak in hisi_acc (Miaoqian Lin)
- Use consistent return for unsupported device feature (Alex Mastro)
- Unwind using the correct memory free callback in vfio/pds (Zilin
Guan)
- Use IRQ_DISABLE_LAZY flag to improve handling of pre-PCI2.3 INTx and
resolve stalled interrupt on ppc64 (Timothy Pearson)
- Enable GB300 in nvgrace-gpu vfio-pci variant driver (Tushar Dave)
- Misc:
- Drop unnecessary ternary conversion in vfio/pci (Xichao Zhao)
- Grammatical fix in nvgrace-gpu (Morduan Zang)
- Update Shameer's email address (Shameer Kolothum)
- Fix document build warning (Alex Williamson)
* tag 'vfio-v6.18-rc1' of https://github.com/awilliam/linux-vfio: (48 commits)
vfio/nvgrace-gpu: Add GB300 SKU to the devid table
vfio/pci: Fix INTx handling on legacy non-PCI 2.3 devices
vfio/pds: replace bitmap_free with vfree
vfio: return -ENOTTY for unsupported device feature
hisi_acc_vfio_pci: Fix reference leak in hisi_acc_vfio_debug_init
vfio/platform: Mark reset drivers for removal
vfio/amba: Mark for removal
MAINTAINERS: Add myself as VFIO-platform reviewer
MAINTAINERS: Add myself as VFIO-platform reviewer
docs: proc.rst: Fix VFIO Device title formatting
vfio: selftests: Fix .gitignore for already tracked files
vfio/cdx: update driver to build without CONFIG_GENERIC_MSI_IRQ
cdx: don't select CONFIG_GENERIC_MSI_IRQ
MAINTAINERS: Update Shameer Kolothum's email address
vfio: selftests: Add a script to help with running VFIO selftests
vfio: selftests: Make iommufd the default iommu_mode
vfio: selftests: Add iommufd mode
vfio: selftests: Add iommufd_compat_type1{,v2} modes
vfio: selftests: Add vfio_type1v2_mode
vfio: selftests: Replicate tests across all iommu_modes
...
|
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Pull documentation updates from Jonathan Corbet:
"It has been a relatively busy cycle in docsland, with changes all
over:
- Bring the kernel memory-model docs into the Sphinx build in the
"literal include" mode.
- Lots of build-infrastructure work, further cleaning up long-term
kernel-doc technical debt. The sphinx-pre-install tool has been
converted to Python and updated for current systems.
- A new tool to detect when documents have been moved and generate
HTML redirects; this can be used on kernel.org (or any other site
hosting the rendered docs) to avoid breaking links.
- Automated processing of the YAML files describing the netlink
protocol.
- A significant update of the maintainer's PGP guide.
... and a seemingly endless series of typo fixes, build-problem fixes,
etc"
* tag 'docs-6.18' of git://git.lwn.net/linux: (193 commits)
Documentation/features: Update feature lists for 6.17-rc7
docs: remove cdomain.py
Documentation/process: submitting-patches: fix typo in "were do"
docs: dev-tools/lkmm: Fix typo of missing file extension
Documentation: trace: histogram: Convert ftrace docs cross-reference
Documentation: trace: histogram-design: Wrap introductory note in note:: directive
Documentation: trace: historgram-design: Separate sched_waking histogram section heading and the following diagram
Documentation: trace: histogram-design: Trim trailing vertices in diagram explanation text
Documentation: trace: histogram: Fix histogram trigger subsection number order
docs: driver-api: fix spelling of "buses".
Documentation: fbcon: Use admonition directives
Documentation: fbcon: Reindent 8th step of attach/detach/unload
Documentation: fbcon: Add boot options and attach/detach/unload section headings
docs: filesystems: sysfs: add remaining top level sysfs directory descriptions
docs: filesystems: sysfs: clarify symlink destinations in dev and bus/devices descriptions
docs: filesystems: sysfs: remove top level sysfs net directory
docs: maintainer: Fix ambiguous subheading formatting
docs: kdoc: a few more dump_typedef() tweaks
docs: kdoc: remove redundant comment stripping in dump_typedef()
docs: kdoc: remove some dead code in dump_typedef()
...
|
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
- "mm, swap: improve cluster scan strategy" from Kairui Song improves
performance and reduces the failure rate of swap cluster allocation
- "support large align and nid in Rust allocators" from Vitaly Wool
permits Rust allocators to set NUMA node and large alignment when
perforning slub and vmalloc reallocs
- "mm/damon/vaddr: support stat-purpose DAMOS" from Yueyang Pan extend
DAMOS_STAT's handling of the DAMON operations sets for virtual
address spaces for ops-level DAMOS filters
- "execute PROCMAP_QUERY ioctl under per-vma lock" from Suren
Baghdasaryan reduces mmap_lock contention during reads of
/proc/pid/maps
- "mm/mincore: minor clean up for swap cache checking" from Kairui Song
performs some cleanup in the swap code
- "mm: vm_normal_page*() improvements" from David Hildenbrand provides
code cleanup in the pagemap code
- "add persistent huge zero folio support" from Pankaj Raghav provides
a block layer speedup by optionalls making the
huge_zero_pagepersistent, instead of releasing it when its refcount
falls to zero
- "kho: fixes and cleanups" from Mike Rapoport adds a few touchups to
the recently added Kexec Handover feature
- "mm: make mm->flags a bitmap and 64-bit on all arches" from Lorenzo
Stoakes turns mm_struct.flags into a bitmap. To end the constant
struggle with space shortage on 32-bit conflicting with 64-bit's
needs
- "mm/swapfile.c and swap.h cleanup" from Chris Li cleans up some swap
code
- "selftests/mm: Fix false positives and skip unsupported tests" from
Donet Tom fixes a few things in our selftests code
- "prctl: extend PR_SET_THP_DISABLE to only provide THPs when advised"
from David Hildenbrand "allows individual processes to opt-out of
THP=always into THP=madvise, without affecting other workloads on the
system".
It's a long story - the [1/N] changelog spells out the considerations
- "Add and use memdesc_flags_t" from Matthew Wilcox gets us started on
the memdesc project. Please see
https://kernelnewbies.org/MatthewWilcox/Memdescs and
https://blogs.oracle.com/linux/post/introducing-memdesc
- "Tiny optimization for large read operations" from Chi Zhiling
improves the efficiency of the pagecache read path
- "Better split_huge_page_test result check" from Zi Yan improves our
folio splitting selftest code
- "test that rmap behaves as expected" from Wei Yang adds some rmap
selftests
- "remove write_cache_pages()" from Christoph Hellwig removes that
function and converts its two remaining callers
- "selftests/mm: uffd-stress fixes" from Dev Jain fixes some UFFD
selftests issues
- "introduce kernel file mapped folios" from Boris Burkov introduces
the concept of "kernel file pages". Using these permits btrfs to
account its metadata pages to the root cgroup, rather than to the
cgroups of random inappropriate tasks
- "mm/pageblock: improve readability of some pageblock handling" from
Wei Yang provides some readability improvements to the page allocator
code
- "mm/damon: support ARM32 with LPAE" from SeongJae Park teaches DAMON
to understand arm32 highmem
- "tools: testing: Use existing atomic.h for vma/maple tests" from
Brendan Jackman performs some code cleanups and deduplication under
tools/testing/
- "maple_tree: Fix testing for 32bit compiles" from Liam Howlett fixes
a couple of 32-bit issues in tools/testing/radix-tree.c
- "kasan: unify kasan_enabled() and remove arch-specific
implementations" from Sabyrzhan Tasbolatov moves KASAN arch-specific
initialization code into a common arch-neutral implementation
- "mm: remove zpool" from Johannes Weiner removes zspool - an
indirection layer which now only redirects to a single thing
(zsmalloc)
- "mm: task_stack: Stack handling cleanups" from Pasha Tatashin makes a
couple of cleanups in the fork code
- "mm: remove nth_page()" from David Hildenbrand makes rather a lot of
adjustments at various nth_page() callsites, eventually permitting
the removal of that undesirable helper function
- "introduce kasan.write_only option in hw-tags" from Yeoreum Yun
creates a KASAN read-only mode for ARM, using that architecture's
memory tagging feature. It is felt that a read-only mode KASAN is
suitable for use in production systems rather than debug-only
- "mm: hugetlb: cleanup hugetlb folio allocation" from Kefeng Wang does
some tidying in the hugetlb folio allocation code
- "mm: establish const-correctness for pointer parameters" from Max
Kellermann makes quite a number of the MM API functions more accurate
about the constness of their arguments. This was getting in the way
of subsystems (in this case CEPH) when they attempt to improving
their own const/non-const accuracy
- "Cleanup free_pages() misuse" from Vishal Moola fixes a number of
code sites which were confused over when to use free_pages() vs
__free_pages()
- "Add Rust abstraction for Maple Trees" from Alice Ryhl makes the
mapletree code accessible to Rust. Required by nouveau and by its
forthcoming successor: the new Rust Nova driver
- "selftests/mm: split_huge_page_test: split_pte_mapped_thp
improvements" from David Hildenbrand adds a fix and some cleanups to
the thp selftesting code
- "mm, swap: introduce swap table as swap cache (phase I)" from Chris
Li and Kairui Song is the first step along the path to implementing
"swap tables" - a new approach to swap allocation and state tracking
which is expected to yield speed and space improvements. This
patchset itself yields a 5-20% performance benefit in some situations
- "Some ptdesc cleanups" from Matthew Wilcox utilizes the new memdesc
layer to clean up the ptdesc code a little
- "Fix va_high_addr_switch.sh test failure" from Chunyu Hu fixes some
issues in our 5-level pagetable selftesting code
- "Minor fixes for memory allocation profiling" from Suren Baghdasaryan
addresses a couple of minor issues in relatively new memory
allocation profiling feature
- "Small cleanups" from Matthew Wilcox has a few cleanups in
preparation for more memdesc work
- "mm/damon: add addr_unit for DAMON_LRU_SORT and DAMON_RECLAIM" from
Quanmin Yan makes some changes to DAMON in furtherance of supporting
arm highmem
- "selftests/mm: Add -Wunreachable-code and fix warnings" from Muhammad
Anjum adds that compiler check to selftests code and fixes the
fallout, by removing dead code
- "Improvements to Victim Process Thawing and OOM Reaper Traversal
Order" from zhongjinji makes a number of improvements in the OOM
killer: mainly thawing a more appropriate group of victim threads so
they can release resources
- "mm/damon: misc fixups and improvements for 6.18" from SeongJae Park
is a bunch of small and unrelated fixups for DAMON
- "mm/damon: define and use DAMON initialization check function" from
SeongJae Park implement reliability and maintainability improvements
to a recently-added bug fix
- "mm/damon/stat: expose auto-tuned intervals and non-idle ages" from
SeongJae Park provides additional transparency to userspace clients
of the DAMON_STAT information
- "Expand scope of khugepaged anonymous collapse" from Dev Jain removes
some constraints on khubepaged's collapsing of anon VMAs. It also
increases the success rate of MADV_COLLAPSE against an anon vma
- "mm: do not assume file == vma->vm_file in compat_vma_mmap_prepare()"
from Lorenzo Stoakes moves us further towards removal of
file_operations.mmap(). This patchset concentrates upon clearing up
the treatment of stacked filesystems
- "mm: Improve mlock tracking for large folios" from Kiryl Shutsemau
provides some fixes and improvements to mlock's tracking of large
folios. /proc/meminfo's "Mlocked" field became more accurate
- "mm/ksm: Fix incorrect accounting of KSM counters during fork" from
Donet Tom fixes several user-visible KSM stats inaccuracies across
forks and adds selftest code to verify these counters
- "mm_slot: fix the usage of mm_slot_entry" from Wei Yang addresses
some potential but presently benign issues in KSM's mm_slot handling
* tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (372 commits)
mm: swap: check for stable address space before operating on the VMA
mm: convert folio_page() back to a macro
mm/khugepaged: use start_addr/addr for improved readability
hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list
alloc_tag: fix boot failure due to NULL pointer dereference
mm: silence data-race in update_hiwater_rss
mm/memory-failure: don't select MEMORY_ISOLATION
mm/khugepaged: remove definition of struct khugepaged_mm_slot
mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL
hugetlb: increase number of reserving hugepages via cmdline
selftests/mm: add fork inheritance test for ksm_merging_pages counter
mm/ksm: fix incorrect KSM counter handling in mm_struct during fork
drivers/base/node: fix double free in register_one_node()
mm: remove PMD alignment constraint in execmem_vmalloc()
mm/memory_hotplug: fix typo 'esecially' -> 'especially'
mm/rmap: improve mlock tracking for large folios
mm/filemap: map entire large folio faultaround
mm/fault: try to map the entire file folio in finish_fault()
mm/rmap: mlock large folios in try_to_unmap_one()
mm/rmap: fix a mlock race condition in folio_referenced_one()
...
|
|
While rare, memory allocation profiling can contain inaccurate counters if
slab object extension vector allocation fails. That allocation might
succeed later but prior to that, slab allocations that would have used
that object extension vector will not be accounted for. To indicate
incorrect counters, "accurate:no" marker is appended to the call site line
in the /proc/allocinfo output. Bump up /proc/allocinfo version to reflect
the change in the file format and update documentation.
Example output with invalid counters:
allocinfo - version: 2.0
0 0 arch/x86/kernel/kdebugfs.c:105 func:create_setup_data_nodes
0 0 arch/x86/kernel/alternative.c:2090 func:alternatives_smp_module_add
0 0 arch/x86/kernel/alternative.c:127 func:__its_alloc accurate:no
0 0 arch/x86/kernel/fpu/regset.c:160 func:xstateregs_set
0 0 arch/x86/kernel/fpu/xstate.c:1590 func:fpstate_realloc
0 0 arch/x86/kernel/cpu/aperfmperf.c:379 func:arch_enable_hybrid_capacity_scale
0 0 arch/x86/kernel/cpu/amd_cache_disable.c:258 func:init_amd_l3_attrs
49152 48 arch/x86/kernel/cpu/mce/core.c:2709 func:mce_device_create accurate:no
32768 1 arch/x86/kernel/cpu/mce/genpool.c:132 func:mce_gen_pool_create
0 0 arch/x86/kernel/cpu/mce/amd.c:1341 func:mce_threshold_create_device
[surenb@google.com: document new "accurate:no" marker]
Fixes: 39d117e04d15 ("alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output")
[akpm@linux-foundation.org: simplification per Usama, reflow text]
[akpm@linux-foundation.org: add newline to prevent docs warning, per Randy]
Link: https://lkml.kernel.org/r/20250915230224.4115531-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Usama Arif <usamaarif642@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: David Wang <00107082@163.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "prctl: extend PR_SET_THP_DISABLE to only provide THPs when
advised", v5.
This will allow individual processes to opt-out of THP = "always" into THP
= "madvise", without affecting other workloads on the system. This has
been extensively discussed on the mailing list and has been summarized
very well by David in the first patch which also includes the links to
alternatives, please refer to the first patch commit message for the
motivation for this series.
Patch 1 adds the PR_THP_DISABLE_EXCEPT_ADVISED flag to implement this,
along with the MMF changes.
Patch 2 is a cleanup patch for tva_flags that will allow the forced
collapse case to be transmitted to vma_thp_disabled (which is done in
patch 3).
Patch 4 adds documentation for PR_SET_THP_DISABLE/PR_GET_THP_DISABLE.
Patches 6-7 implement the selftests for PR_SET_THP_DISABLE for completely
disabling THPs (old behaviour) and only enabling it at advise
(PR_THP_DISABLE_EXCEPT_ADVISED).
This patch (of 7):
People want to make use of more THPs, for example, moving from the "never"
system policy to "madvise", or from "madvise" to "always".
While this is great news for every THP desperately waiting to get
allocated out there, apparently there are some workloads that require a
bit of care during that transition: individual processes may need to
opt-out from this behavior for various reasons, and this should be
permitted without needing to make all other workloads on the system
similarly opt-out.
The following scenarios are imaginable:
(1) Switch from "none" system policy to "madvise"/"always", but keep THPs
disabled for selected workloads.
(2) Stay at "none" system policy, but enable THPs for selected
workloads, making only these workloads use the "madvise" or "always"
policy.
(3) Switch from "madvise" system policy to "always", but keep the
"madvise" policy for selected workloads: allocate THPs only when
advised.
(4) Stay at "madvise" system policy, but enable THPs even when not advised
for selected workloads -- "always" policy.
Once can emulate (2) through (1), by setting the system policy to
"madvise"/"always" while disabling THPs for all processes that don't want
THPs. It requires configuring all workloads, but that is a user-space
problem to sort out.
(4) can be emulated through (3) in a similar way.
Back when (1) was relevant in the past, as people started enabling THPs,
we added PR_SET_THP_DISABLE, so relevant workloads that were not ready yet
(i.e., used by Redis) were able to just disable THPs completely. Redis
still implements the option to use this interface to disable THPs
completely.
With PR_SET_THP_DISABLE, we added a way to force-disable THPs for a
workload -- a process, including fork+exec'ed process hierarchy. That
essentially made us support (1): simply disable THPs for all workloads
that are not ready for THPs yet, while still enabling THPs system-wide.
The quest for handling (3) and (4) started, but current approaches
(completely new prctl, options to set other policies per process,
alternatives to prctl -- mctrl, cgroup handling) don't look particularly
promising. Likely, the future will use bpf or something similar to
implement better policies, in particular to also make better decisions
about THP sizes to use, but this will certainly take a while as that work
just started.
Long story short: a simple enable/disable is not really suitable for the
future, so we're not willing to add completely new toggles.
While we could emulate (3)+(4) through (1)+(2) by simply disabling THPs
completely for these processes, this is a step backwards, because these
processes can no longer allocate THPs in regions where THPs were
explicitly advised: regions flagged as VM_HUGEPAGE. Apparently, that
imposes a problem for relevant workloads, because "not THPs" is certainly
worse than "THPs only when advised".
Could we simply relax PR_SET_THP_DISABLE, to "disable THPs unless not
explicitly advised by the app through MAD_HUGEPAGE"? *maybe*, but this
would change the documented semantics quite a bit, and the versatility to
use it for debugging purposes, so I am not 100% sure that is what we want
-- although it would certainly be much easier.
So instead, as an easy way forward for (3) and (4), add an option to
make PR_SET_THP_DISABLE disable *less* THPs for a process.
In essence, this patch:
(A) Adds PR_THP_DISABLE_EXCEPT_ADVISED, to be used as a flag in arg3
of prctl(PR_SET_THP_DISABLE) when disabling THPs (arg2 != 0).
prctl(PR_SET_THP_DISABLE, 1, PR_THP_DISABLE_EXCEPT_ADVISED).
(B) Makes prctl(PR_GET_THP_DISABLE) return 3 if
PR_THP_DISABLE_EXCEPT_ADVISED was set while disabling.
Previously, it would return 1 if THPs were disabled completely. Now
it returns the set flags as well: 3 if PR_THP_DISABLE_EXCEPT_ADVISED
was set.
(C) Renames MMF_DISABLE_THP to MMF_DISABLE_THP_COMPLETELY, to express
the semantics clearly.
Fortunately, there are only two instances outside of prctl() code.
(D) Adds MMF_DISABLE_THP_EXCEPT_ADVISED to express "no THP except for VMAs
with VM_HUGEPAGE" -- essentially "thp=madvise" behavior
Fortunately, we only have to extend vma_thp_disabled().
(E) Indicates "THP_enabled: 0" in /proc/pid/status only if THPs are
disabled completely
Only indicating that THPs are disabled when they are really disabled
completely, not only partially.
For now, we don't add another interface to obtained whether THPs
are disabled partially (PR_THP_DISABLE_EXCEPT_ADVISED was set). If
ever required, we could add a new entry.
The documented semantics in the man page for PR_SET_THP_DISABLE "is
inherited by a child created via fork(2) and is preserved across
execve(2)" is maintained. This behavior, for example, allows for
disabling THPs for a workload through the launching process (e.g., systemd
where we fork() a helper process to then exec()).
For now, MADV_COLLAPSE will *fail* in regions without VM_HUGEPAGE and
VM_NOHUGEPAGE. As MADV_COLLAPSE is a clear advise that user space thinks
a THP is a good idea, we'll enable that separately next (requiring a bit
of cleanup first).
There is currently not way to prevent that a process will not issue
PR_SET_THP_DISABLE itself to re-enable THP. There are not really known
users for re-enabling it, and it's against the purpose of the original
interface. So if ever required, we could investigate just forbidding to
re-enable them, or make this somehow configurable.
Link: https://lkml.kernel.org/r/20250815135549.130506-1-usamaarif642@gmail.com
Link: https://lkml.kernel.org/r/20250815135549.130506-2-usamaarif642@gmail.com
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: Usama Arif <usamaarif642@gmail.com>
Tested-by: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Usama Arif <usamaarif642@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mari |
