kernel/Documentation/admin-guide/cgroup-v1, branch linux-rolling-stable

Update Christoph's Email address and make it consistent

2025-05-13T06:50:31Z

Use cl@gentwo.org throughout and remove the old email addresses. Link: https://lkml.kernel.org/r/8b962f57-4d98-cbb0-cd82-b6ba456733e8@gentwo.org Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton

Merge tag 'mm-stable-2025-03-30-16-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-04-01T16:29:18Z

Pull MM updates from Andrew Morton: - The series "Enable strict percpu address space checks" from Uros Bizjak uses x86 named address space qualifiers to provide compile-time checking of percpu area accesses. This has caused a small amount of fallout - two or three issues were reported. In all cases the calling code was found to be incorrect. - The series "Some cleanup for memcg" from Chen Ridong implements some relatively monir cleanups for the memcontrol code. - The series "mm: fixes for device-exclusive entries (hmm)" from David Hildenbrand fixes a boatload of issues which David found then using device-exclusive PTE entries when THP is enabled. More work is needed, but this makes thins better - our own HMM selftests now succeed. - The series "mm: zswap: remove z3fold and zbud" from Yosry Ahmed remove the z3fold and zbud implementations. They have been deprecated for half a year and nobody has complained. - The series "mm: further simplify VMA merge operation" from Lorenzo Stoakes implements numerous simplifications in this area. No runtime effects are anticipated. - The series "mm/madvise: remove redundant mmap_lock operations from process_madvise()" from SeongJae Park rationalizes the locking in the madvise() implementation. Performance gains of 20-25% were observed in one MADV_DONTNEED microbenchmark. - The series "Tiny cleanup and improvements about SWAP code" from Baoquan He contains a number of touchups to issues which Baoquan noticed when working on the swap code. - The series "mm: kmemleak: Usability improvements" from Catalin Marinas implements a couple of improvements to the kmemleak user-visible output. - The series "mm/damon/paddr: fix large folios access and schemes handling" from Usama Arif provides a couple of fixes for DAMON's handling of large folios. - The series "mm/damon/core: fix wrong and/or useless damos_walk() behaviors" from SeongJae Park fixes a few issues with the accuracy of kdamond's walking of DAMON regions. - The series "expose mapping wrprotect, fix fb_defio use" from Lorenzo Stoakes changes the interaction between framebuffer deferred-io and core MM. No functional changes are anticipated - this is preparatory work for the future removal of page structure fields. - The series "mm/damon: add support for hugepage_size DAMOS filter" from Usama Arif adds a DAMOS filter which permits the filtering by huge page sizes. - The series "mm: permit guard regions for file-backed/shmem mappings" from Lorenzo Stoakes extends the guard region feature from its present "anon mappings only" state. The feature now covers shmem and file-backed mappings. - The series "mm: batched unmap lazyfree large folios during reclamation" from Barry Song cleans up and speeds up the unmapping for pte-mapped large folios. - The series "reimplement per-vma lock as a refcount" from Suren Baghdasaryan puts the vm_lock back into the vma. Our reasons for pulling it out were largely bogus and that change made the code more messy. This patchset provides small (0-10%) improvements on one microbenchmark. - The series "Docs/mm/damon: misc DAMOS filters documentation fixes and improves" from SeongJae Park does some maintenance work on the DAMON docs. - The series "hugetlb/CMA improvements for large systems" from Frank van der Linden addresses a pile of issues which have been observed when using CMA on large machines. - The series "mm/damon: introduce DAMOS filter type for unmapped pages" from SeongJae Park enables users of DMAON/DAMOS to filter my the page's mapped/unmapped status. - The series "zsmalloc/zram: there be preemption" from Sergey Senozhatsky teaches zram to run its compression and decompression operations preemptibly. - The series "selftests/mm: Some cleanups from trying to run them" from Brendan Jackman fixes a pile of unrelated issues which Brendan encountered while runnimg our selftests. - The series "fs/proc/task_mmu: add guard region bit to pagemap" from Lorenzo Stoakes permits userspace to use /proc/pid/pagemap to determine whether a particular page is a guard page. - The series "mm, swap: remove swap slot cache" from Kairui Song removes the swap slot cache from the allocation path - it simply wasn't being effective. - The series "mm: cleanups for device-exclusive entries (hmm)" from David Hildenbrand implements a number of unrelated cleanups in this code. - The series "mm: Rework generic PTDUMP configs" from Anshuman Khandual implements a number of preparatoty cleanups to the GENERIC_PTDUMP Kconfig logic. - The series "mm/damon: auto-tune aggregation interval" from SeongJae Park implements a feedback-driven automatic tuning feature for DAMON's aggregation interval tuning. - The series "Fix lazy mmu mode" from Ryan Roberts fixes some issues in powerpc, sparc and x86 lazy MMU implementations. Ryan did this in preparation for implementing lazy mmu mode for arm64 to optimize vmalloc. - The series "mm/page_alloc: Some clarifications for migratetype fallback" from Brendan Jackman reworks some commentary to make the code easier to follow. - The series "page_counter cleanup and size reduction" from Shakeel Butt cleans up the page_counter code and fixes a size increase which we accidentally added late last year. - The series "Add a command line option that enables control of how many threads should be used to allocate huge pages" from Thomas Prescher does that. It allows the careful operator to significantly reduce boot time by tuning the parallalization of huge page initialization. - The series "Fix calculations in trace_balance_dirty_pages() for cgwb" from Tang Yizhou fixes the tracing output from the dirty page balancing code. - The series "mm/damon: make allow filters after reject filters useful and intuitive" from SeongJae Park improves the handling of allow and reject filters. Behaviour is made more consistent and the documention is updated accordingly. - The series "Switch zswap to object read/write APIs" from Yosry Ahmed updates zswap to the new object read/write APIs and thus permits the removal of some legacy code from zpool and zsmalloc. - The series "Some trivial cleanups for shmem" from Baolin Wang does as it claims. - The series "fs/dax: Fix ZONE_DEVICE page reference counts" from Alistair Popple regularizes the weird ZONE_DEVICE page refcount handling in DAX, permittig the removal of a number of special-case checks. - The series "refactor mremap and fix bug" from Lorenzo Stoakes is a preparatoty refactoring and cleanup of the mremap() code. - The series "mm: MM owner tracking for large folios (!hugetlb) + CONFIG_NO_PAGE_MAPCOUNT" from David Hildenbrand reworks the manner in which we determine whether a large folio is known to be mapped exclusively into a single MM. - The series "mm/damon: add sysfs dirs for managing DAMOS filters based on handling layers" from SeongJae Park adds a couple of new sysfs directories to ease the management of DAMON/DAMOS filters. - The series "arch, mm: reduce code duplication in mem_init()" from Mike Rapoport consolidates many per-arch implementations of mem_init() into code generic code, where that is practical. - The series "mm/damon/sysfs: commit parameters online via damon_call()" from SeongJae Park continues the cleaning up of sysfs access to DAMON internal data. - The series "mm: page_ext: Introduce new iteration API" from Luiz Capitulino reworks the page_ext initialization to fix a boot-time crash which was observed with an unusual combination of compile and cmdline options. - The series "Buddy allocator like (or non-uniform) folio split" from Zi Yan reworks the code to split a folio into smaller folios. The main benefit is lessened memory consumption: fewer post-split folios are generated. - The series "Minimize xa_node allocation during xarry split" from Zi Yan reduces the number of xarray xa_nodes which are generated during an xarray split. - The series "drivers/base/memory: Two cleanups" from Gavin Shan performs some maintenance work on the drivers/base/memory code. - The series "Add tracepoints for lowmem reserves, watermarks and totalreserve_pages" from Martin Liu adds some more tracepoints to the page allocator code. - The series "mm/madvise: cleanup requests validations and classifications" from SeongJae Park cleans up some warts which SeongJae observed during his earlier madvise work. - The series "mm/hwpoison: Fix regressions in memory failure handling" from Shuai Xue addresses two quite serious regressions which Shuai has observed in the memory-failure implementation. - The series "mm: reliable huge page allocator" from Johannes Weiner makes huge page allocations cheaper and more reliable by reducing fragmentation. - The series "Minor memcg cleanups & prep for memdescs" from Matthew Wilcox is preparatory work for the future implementation of memdescs. - The series "track memory used by balloon drivers" from Nico Pache introduces a way to track memory used by our various balloon drivers. - The series "mm/damon: introduce DAMOS filter type for active pages" from Nhat Pham permits users to filter for active/inactive pages, separately for file and anon pages. - The series "Adding Proactive Memory Reclaim Statistics" from Hao Jia separates the proactive reclaim statistics from the direct reclaim statistics. - The series "mm/vmscan: don't try to reclaim hwpoison folio" from Jinjiang Tu fixes our handling of hwpoisoned pages within the reclaim code. * tag 'mm-stable-2025-03-30-16-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (431 commits) mm/page_alloc: remove unnecessary __maybe_unused in order_to_pindex() x86/mm: restore early initialization of high_memory for 32-bits mm/vmscan: don't try to reclaim hwpoison folio mm/hwpoison: introduce folio_contain_hwpoisoned_page() helper cgroup: docs: add pswpin and pswpout items in cgroup v2 doc mm: vmscan: split proactive reclaim statistics from direct reclaim statistics selftests/mm: speed up split_huge_page_test selftests/mm: uffd-unit-tests support for hugepages > 2M docs/mm/damon/design: document active DAMOS filter type mm/damon: implement a new DAMOS filter type for active pages fs/dax: don't disassociate zero page entries MM documentation: add "Unaccepted" meminfo entry selftests/mm: add commentary about 9pfs bugs fork: use __vmalloc_node() for stack allocation docs/mm: Physical Memory: Populate the "Zones" section xen: balloon: update the NR_BALLOON_PAGES state hv_balloon: update the NR_BALLOON_PAGES state balloon_compaction: update the NR_BALLOON_PAGES state meminfo: add a per node counter for balloon drivers mm: remove references to folio in __memcg_kmem_uncharge_page() ...

mm: stop maintaining the per-page mapcount of large folios (CONFIG_NO_PAGE_MAPCOUNT)

2025-03-18T05:06:48Z

Everything is in place to stop using the per-page mapcounts in large folios: the mapcount of tail pages will always be logically 0 (-1 value), just like it currently is for hugetlb folios already, and the page mapcount of the head page is either 0 (-1 value) or contains a page type (e.g., hugetlb). Maintaining _nr_pages_mapped without per-page mapcounts is impossible, so that one also has to go with CONFIG_NO_PAGE_MAPCOUNT. There are two remaining implications: (1) Per-node, per-cgroup and per-lruvec stats of "NR_ANON_MAPPED" ("mapped anonymous memory") and "NR_FILE_MAPPED" ("mapped file memory"): As soon as any page of the folio is mapped -- folio_mapped() -- we now account the complete folio as mapped. Once the last page is unmapped -- !folio_mapped() -- we account the complete folio as unmapped. This implies that ... * "AnonPages" and "Mapped" in /proc/meminfo and /sys/devices/system/node/*/meminfo * cgroup v2: "anon" and "file_mapped" in "memory.stat" and "memory.numa_stat" * cgroup v1: "rss" and "mapped_file" in "memory.stat" and "memory.numa_stat ... can now appear higher than before. But note that these folios do consume that memory, simply not all pages are actually currently mapped. It's worth nothing that other accounting in the kernel (esp. cgroup charging on allocation) is not affected by this change. [why oh why is "anon" called "rss" in cgroup v1] (2) Detecting partial mappings Detecting whether anon THPs are partially mapped gets a bit more unreliable. As long as a single MM maps such a large folio ("exclusively mapped"), we can reliably detect it. Especially before fork() / after a short-lived child process quit, we will detect partial mappings reliably, which is the common case. In essence, if the average per-page mapcount in an anon THP is < 1, we know for sure that we have a partial mapping. However, as soon as multiple MMs are involved, we might miss detecting partial mappings: this might be relevant with long-lived child processes. If we have a fully-mapped anon folio before fork(), once our child processes and our parent all unmap (zap/COW) the same pages (but not the complete folio), we might not detect the partial mapping. However, once the child processes quit we would detect the partial mapping. How relevant this case is in practice remains to be seen. Swapout/migration will likely mitigate this. In the future, RMAP walkers could check for that for that case (e.g., when collecting access bits during reclaim) and simply flag them for deferred-splitting. Link: https://lkml.kernel.org/r/20250303163014.1128035-21-david@redhat.com Signed-off-by: David Hildenbrand Cc: Andy Lutomirks^H^Hski Cc: Borislav Betkov Cc: Dave Hansen Cc: Ingo Molnar Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Kirill A. Shutemov Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcow (Oracle) Cc: Michal Koutn Cc: Muchun Song Cc: tejun heo Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: Zefan Li Signed-off-by: Andrew Morton

cgroup: Add deprecation message to legacy freezer controller

2025-03-11T19:22:54Z

As explained in the commit 76f969e8948d8 ("cgroup: cgroup v2 freezer"), the original freezer is imperfect, some users may unwittingly rely on it when there exists the alternative of v2. Print a message when it happens and explain that in the docs. Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo

mm: Add transformation message for per-memcg swappiness

2025-03-11T19:22:54Z

The concept of per-memcg swappiness has never landed well in memcg for cgroup v2. Add a message to users who use it on v1 hierarchy. Decreased swappiness transforms to memory.swap.max=0 whereas increased swappiness transforms into active memory.reclaim operation. Link: https://lore.kernel.org/r/1577252208-32419-1-git-send-email-teawater@gmail.com/ Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo

memcg-v1: fully deprecate move_charge_at_immigrate

2024-11-07T04:11:18Z

Patch series "memcg-v1: fully deprecate charge moving". The memcg v1's charge moving feature has been deprecated for almost 2 years and the kernel warns if someone try to use it. This warning has been backported to all stable kernel and there have not been any report of the warning or the request to support this feature anymore. Let's proceed to fully deprecate this feature. This patch (of 6): Proceed with the complete deprecation of memcg v1's charge moving feature. The deprecation warning has been in the kernel for almost two years and has been ported to all stable kernel since. Now is the time to fully deprecate this feature. Link: https://lkml.kernel.org/r/20241025012304.2473312-1-shakeel.butt@linux.dev Link: https://lkml.kernel.org/r/20241025012304.2473312-2-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Reviewed-by: Roman Gushchin Acked-by: Michal Hocko Acked-by: Johannes Weiner Cc: Hugh Dickins Cc: Muchun Song Cc: Yosry Ahmed Signed-off-by: Andrew Morton

memcg: initiate deprecation of pressure_level

2024-09-02T03:26:21Z

The pressure_level in memcg v1 provides memory pressure notifications to the user space. At the moment it provides notifications for three levels of memory pressure i.e. low, medium and critical, which are defined based on internal memory reclaim implementation details. More specifically the ratio of scanned and reclaimed pages during a memory reclaim. However this is not robust as there are workloads with mostly unreclaimable user memory or kernel memory. For v2, the users can use PSI for memory pressure status of the system or the cgroup. Let's start the deprecation process for pressure_level and add warnings to gather the info on how the current users are using this interface and how they can be used to PSI. Link: https://lkml.kernel.org/r/20240814220021.3208384-5-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Reviewed-by: T.J. Mercier Acked-by: Michal Hocko Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Muchun Song Signed-off-by: Andrew Morton

memcg: initiate deprecation of oom_control

2024-09-02T03:26:21Z

The oom_control provides functionality to disable memcg oom-killer, notifications on oom-kill and reading the stats regarding oom-kills. This interface was mainly introduced to provide functionality for userspace oom-killers. However it is not robust enough and only supports OOM handling in the page fault path. For v2, the users can use the combination of memory.events notifications, memory.high and PSI to provide userspace OOM-killing functionality. Actually LMKD in Android and OOMd in systemd and Meta infrastructure already use PSI in combination with other stats to implement userspace OOM-killing. Let's start the deprecation process for v1 and gather the info on how the current users are using this interface and work on providing a more robust functionality in v2. Link: https://lkml.kernel.org/r/20240814220021.3208384-4-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Reviewed-by: T.J. Mercier Acked-by: Michal Hocko Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Muchun Song Signed-off-by: Andrew Morton

memcg: initiate deprecation of v1 soft limit

2024-09-02T03:26:20Z

Memcg v1 provides soft limit functionality for the best effort memory sharing between multiple workloads on a system. It is usually triggered through kswapd and at the moment does not reclaim kernel memory. Memcg v2 provides more straightforward best effort (memory.low) and hard protection (memory.min) functionalities. Let's initiate the deprecation of soft limit from v1 and gather if v2 needs something more to move the existing v1 users to v2 regarding soft limit. Link: https://lkml.kernel.org/r/20240814220021.3208384-3-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Reviewed-by: T.J. Mercier Acked-by: Michal Hocko Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Muchun Song Signed-off-by: Andrew Morton

memcg: initiate deprecation of v1 tcp accounting

2024-09-02T03:26:20Z

Patch series "memcg: initiate deprecation of v1 features", v2. Start the deprecation process of the memcg v1 features which we discussed during LSFMMBPF 2024 [1]. For now add the warnings to collect the information on how the current users are using these features. Next we will work on providing better alternatives in v2 (if needed) and fully deprecate these features. Link: https://lwn.net/Articles/974575 [1] This patch (of 4): Memcg v1 provides opt-in TCP memory accounting feature. However it is mostly unused due to its performance impact on the network traffic. In v2, the TCP memory is accounted in the regular memory usage and is transparent to the users but they can observe the TCP memory usage through memcg stats. Let's initiate the deprecation process of memcg v1's tcp accounting functionality and add warnings to gather if there are any users and if there are, collect how they are using it and plan to provide them better alternative in v2. Link: https://lkml.kernel.org/r/20240814220021.3208384-1-shakeel.butt@linux.dev Link: https://lkml.kernel.org/r/20240814220021.3208384-2-shakeel.butt@linux.dev Signed-off-by: Shakeel Butt Reviewed-by: T.J. Mercier Acked-by: Michal Hocko Acked-by: Roman Gushchin Cc: Johannes Weiner Cc: Muchun Song Signed-off-by: Andrew Morton