kernel/linux.git/Documentation/admin-guide/sysctl/vm.rst, branch v6.6.131

Documentation: admin-guide: correct spelling

2023-02-02T18:04:42+00:00

Correct spelling problems for Documentation/admin-guide/ as reported by codespell. Signed-off-by: Randy Dunlap Reviewed-by: Mukesh Ojha Cc: Tejun Heo Cc: Zefan Li Cc: Johannes Weiner Cc: cgroups@vger.kernel.org Cc: Alasdair Kergon Cc: Mike Snitzer Cc: dm-devel@redhat.com Cc: Mauro Carvalho Chehab Cc: linux-media@vger.kernel.org Cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20230129231053.20863-2-rdunlap@infradead.org Signed-off-by: Jonathan Corbet

userfaultfd: update documentation to describe /dev/userfaultfd

2022-09-12T03:25:49+00:00

Explain the different ways to create a new userfaultfd, and how access control works for each way. [axelrasmussen@google.com: improve wording in documentation, per Mike] Link: https://lkml.kernel.org/r/20220819205201.658693-5-axelrasmussen@google.com Link: https://lkml.kernel.org/r/20220808175614.3885028-5-axelrasmussen@google.com Signed-off-by: Axel Rasmussen Acked-by: Peter Xu Reviewed-by: Shuah Khan Cc: Al Viro Cc: Dave Hansen Cc: Dmitry V. Levin Cc: Gleb Fotengauer-Malinovskiy Cc: Hugh Dickins Cc: Jan Kara Cc: Jonathan Corbet Cc: Mel Gorman Cc: Mike Kravetz Cc: Mike Rapoport Cc: Nadav Amit Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zhang Yi Cc: Mike Rapoport Signed-off-by: Andrew Morton

mm: hugetlb_vmemmap: introduce the name HVO

2022-08-09T01:06:42+00:00

It it inconvenient to mention the feature of optimizing vmemmap pages associated with HugeTLB pages when communicating with others since there is no specific or abbreviated name for it when it is first introduced. Let us give it a name HVO (HugeTLB Vmemmap Optimization) from now. This commit also updates the document about "hugetlb_free_vmemmap" by the way discussed in thread [1]. Link: https://lore.kernel.org/all/21aae898-d54d-cc4b-a11f-1bb7fddcfffa@redhat.com/ [1] Link: https://lkml.kernel.org/r/20220628092235.91270-4-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Oscar Salvador Reviewed-by: Mike Kravetz Cc: Anshuman Khandual Cc: Catalin Marinas Cc: David Hildenbrand Cc: Jonathan Corbet Cc: Will Deacon Cc: Xiongchun Duan Signed-off-by: Andrew Morton

mm: memory_hotplug: make hugetlb_optimize_vmemmap compatible with memmap_on_memory

2022-07-04T01:08:49+00:00

For now, the feature of hugetlb_free_vmemmap is not compatible with the feature of memory_hotplug.memmap_on_memory, and hugetlb_free_vmemmap takes precedence over memory_hotplug.memmap_on_memory. However, someone wants to make memory_hotplug.memmap_on_memory takes precedence over hugetlb_free_vmemmap since memmap_on_memory makes it more likely to succeed memory hotplug in close-to-OOM situations. So the decision of making hugetlb_free_vmemmap take precedence is not wise and elegant. The proper approach is to have hugetlb_vmemmap.c do the check whether the section which the HugeTLB pages belong to can be optimized. If the section's vmemmap pages are allocated from the added memory block itself, hugetlb_free_vmemmap should refuse to optimize the vmemmap, otherwise, do the optimization. Then both kernel parameters are compatible. So this patch introduces VmemmapSelfHosted to mask any non-optimizable vmemmap pages. The hugetlb_vmemmap can use this flag to detect if a vmemmap page can be optimized. [songmuchun@bytedance.com: walk vmemmap page tables to avoid false-positive] Link: https://lkml.kernel.org/r/20220620110616.12056-3-songmuchun@bytedance.com Link: https://lkml.kernel.org/r/20220617135650.74901-3-songmuchun@bytedance.com Signed-off-by: Muchun Song Co-developed-by: Oscar Salvador Signed-off-by: Oscar Salvador Acked-by: David Hildenbrand Cc: Jonathan Corbet Cc: Mike Kravetz Cc: Paul E. McKenney Cc: Xiongchun Duan Signed-off-by: Andrew Morton

docs: rename Documentation/vm to Documentation/mm

2022-06-27T19:52:53+00:00

so it will be consistent with code mm directory and with Documentation/admin-guide/mm and won't be confused with virtual machines. Signed-off-by: Mike Rapoport Suggested-by: Matthew Wilcox Tested-by: Ira Weiny Acked-by: Jonathan Corbet Acked-by: Wu XiangCheng

mm: hugetlb_vmemmap: add hugetlb_optimize_vmemmap sysctl

2022-05-13T23:48:56+00:00

We must add hugetlb_free_vmemmap=on (or "off") to the boot cmdline and reboot the server to enable or disable the feature of optimizing vmemmap pages associated with HugeTLB pages. However, rebooting usually takes a long time. So add a sysctl to enable or disable the feature at runtime without rebooting. Why we need this? There are 3 use cases. 1) The feature of minimizing overhead of struct page associated with each HugeTLB is disabled by default without passing "hugetlb_free_vmemmap=on" to the boot cmdline. When we (ByteDance) deliver the servers to the users who want to enable this feature, they have to configure the grub (change boot cmdline) and reboot the servers, whereas rebooting usually takes a long time (we have thousands of servers). It's a very bad experience for the users. So we need a approach to enable this feature after rebooting. This is a use case in our practical environment. 2) Some use cases are that HugeTLB pages are allocated 'on the fly' instead of being pulled from the HugeTLB pool, those workloads would be affected with this feature enabled. Those workloads could be identified by the characteristics of they never explicitly allocating huge pages with 'nr_hugepages' but only set 'nr_overcommit_hugepages' and then let the pages be allocated from the buddy allocator at fault time. We can confirm it is a real use case from the commit 099730d67417. For those workloads, the page fault time could be ~2x slower than before. We suspect those users want to disable this feature if the system has enabled this before and they don't think the memory savings benefit is enough to make up for the performance drop. 3) If the workload which wants vmemmap pages to be optimized and the workload which wants to set 'nr_overcommit_hugepages' and does not want the extera overhead at fault time when the overcommitted pages be allocated from the buddy allocator are deployed in the same server. The user could enable this feature and set 'nr_hugepages' and 'nr_overcommit_hugepages', then disable the feature. In this case, the overcommited HugeTLB pages will not encounter the extra overhead at fault time. Link: https://lkml.kernel.org/r/20220512041142.39501-5-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Mike Kravetz Cc: Jonathan Corbet Cc: Luis Chamberlain Cc: Kees Cook Cc: Iurii Zaikin Cc: Oscar Salvador Cc: David Hildenbrand Cc: Masahiro Yamada Cc: Xiongchun Duan Signed-off-by: Andrew Morton

Documentation/sysctl: document page_lock_unfairness

2022-04-29T06:16:01+00:00

commit 5ef64cc8987a ("mm: allow a controlled amount of unfairness in the page lock") introduced a new systctl but no accompanying documentation. Add a simple entry to the documentation. Link: https://lkml.kernel.org/r/20220325164437.120246-1-jsavitz@redhat.com Signed-off-by: Joel Savitz Cc: Jonathan Corbet Cc: Vlastimil Babka Cc: Mel Gorman Cc: Dave Hansen Cc: Suren Baghdasaryan Cc: Mike Rapoport Cc: "zhangyi (F)" Cc: Charan Teja Reddy Cc: Linus Torvalds Signed-off-by: Andrew Morton

mm/pagealloc: sysctl: change watermark_scale_factor max limit to 30%

2022-01-15T14:30:29+00:00

For embedded systems with low total memory, having to run applications with relatively large memory requirements, 10% max limitation for watermark_scale_factor poses an issue of triggering direct reclaim every time such application is started. This results in slow application startup times and bad end-user experience. By increasing watermark_scale_factor max limit we allow vendors more flexibility to choose the right level of kswapd aggressiveness for their device and workload requirements. Link: https://lkml.kernel.org/r/20211124193604.2758863-1-surenb@google.com Signed-off-by: Suren Baghdasaryan Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Lukas Middendorf Cc: Antti Palosaari Cc: Luis Chamberlain Cc: Kees Cook Cc: Iurii Zaikin Cc: Dave Hansen Cc: Vlastimil Babka Cc: Mel Gorman Cc: Jonathan Corbet Cc: Zhang Yi Cc: Fengfei Xi Cc: Mike Rapoport Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: compaction: support triggering of proactive compaction by user

2021-09-03T16:58:17+00:00

The proactive compaction[1] gets triggered for every 500msec and run compaction on the node for COMPACTION_HPAGE_ORDER (usually order-9) pages based on the value set to sysctl.compaction_proactiveness. Triggering the compaction for every 500msec in search of COMPACTION_HPAGE_ORDER pages is not needed for all applications, especially on the embedded system usecases which may have few MB's of RAM. Enabling the proactive compaction in its state will endup in running almost always on such systems. Other side, proactive compaction can still be very much useful for getting a set of higher order pages in some controllable manner(controlled by using the sysctl.compaction_proactiveness). So, on systems where enabling the proactive compaction always may proove not required, can trigger the same from user space on write to its sysctl interface. As an example, say app launcher decide to launch the memory heavy application which can be launched fast if it gets more higher order pages thus launcher can prepare the system in advance by triggering the proactive compaction from userspace. This triggering of proactive compaction is done on a write to sysctl.compaction_proactiveness by user. [1]https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=facdaa917c4d5a376d09d25865f5a863f906234a [akpm@linux-foundation.org: tweak vm.rst, per Mike] Link: https://lkml.kernel.org/r/1627653207-12317-1-git-send-email-charante@codeaurora.org Signed-off-by: Charan Teja Reddy Acked-by: Vlastimil Babka Acked-by: Rafael Aquini Cc: Mike Rapoport Cc: Luis Chamberlain Cc: Kees Cook Cc: Iurii Zaikin Cc: Dave Hansen Cc: Mel Gorman Cc: Nitin Gupta Cc: Jonathan Corbet Cc: Khalid Aziz Cc: David Rientjes Cc: Vinayak Menon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block

2021-06-30T19:12:56+00:00

Pull core block updates from Jens Axboe: - disk events cleanup (Christoph) - gendisk and request queue allocation simplifications (Christoph) - bdev_disk_changed cleanups (Christoph) - IO priority improvements (Bart) - Chained bio completion trace fix (Edward) - blk-wbt fixes (Jan) - blk-wbt enable/disable fix (Zhang) - Scheduler dispatch improvements (Jan, Ming) - Shared tagset scheduler improvements (John) - BFQ updates (Paolo, Luca, Pietro) - BFQ lock inversion fix (Jan) - Documentation improvements (Kir) - CLONE_IO block cgroup fix (Tejun) - Remove of ancient and deprecated block dump feature (zhangyi) - Discard merge fix (Ming) - Misc fixes or followup fixes (Colin, Damien, Dan, Long, Max, Thomas, Yang) * tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block: (129 commits) block: fix discard request merge block/mq-deadline: Remove a WARN_ON_ONCE() call blk-mq: update hctx->dispatch_busy in case of real scheduler blk: Fix lock inversion between ioc lock and bfqd lock bfq: Remove merged request already in bfq_requests_merged() block: pass a gendisk to bdev_disk_changed block: move bdev_disk_changed block: add the events* attributes to disk_attrs block: move the disk events code to a separate file block: fix trace completion for chained bio block/partitions/msdos: Fix typo inidicator -> indicator block, bfq: reset waker pointer with shared queues block, bfq: check waker only for queues with no in-flight I/O block, bfq: avoid delayed merge of async queues block, bfq: boost throughput by extending queue-merging times block, bfq: consider also creation time in delayed stable merge block, bfq: fix delayed stable merge check block, bfq: let also stably merged queues enjoy weight raising blk-wbt: make sure throttle is enabled properly blk-wbt: introduce a new disable state to prevent false positive by rwb_enabled() ...