From ee65728e103bb7dd99d8604bf6c7aa89c7d7e446 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Mon, 27 Jun 2022 09:00:26 +0300 Subject: docs: rename Documentation/vm to Documentation/mm 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 --- Documentation/ABI/testing/sysfs-kernel-mm-ksm | 2 +- Documentation/ABI/testing/sysfs-kernel-slab | 4 +- Documentation/admin-guide/kernel-parameters.txt | 10 +- Documentation/admin-guide/mm/concepts.rst | 2 +- Documentation/admin-guide/mm/damon/index.rst | 2 +- Documentation/admin-guide/mm/damon/reclaim.rst | 2 +- Documentation/admin-guide/mm/damon/usage.rst | 8 +- Documentation/admin-guide/sysctl/vm.rst | 2 +- Documentation/core-api/index.rst | 2 +- Documentation/filesystems/proc.rst | 2 +- Documentation/index.rst | 2 +- Documentation/mm/active_mm.rst | 91 ++++ Documentation/mm/arch_pgtable_helpers.rst | 260 +++++++++ Documentation/mm/balance.rst | 102 ++++ Documentation/mm/bootmem.rst | 5 + Documentation/mm/damon/api.rst | 20 + Documentation/mm/damon/design.rst | 176 ++++++ Documentation/mm/damon/faq.rst | 50 ++ Documentation/mm/damon/index.rst | 29 + Documentation/mm/free_page_reporting.rst | 40 ++ Documentation/mm/frontswap.rst | 266 +++++++++ Documentation/mm/highmem.rst | 167 ++++++ Documentation/mm/hmm.rst | 452 ++++++++++++++++ Documentation/mm/hugetlbfs_reserv.rst | 596 +++++++++++++++++++++ Documentation/mm/hwpoison.rst | 184 +++++++ Documentation/mm/index.rst | 68 +++ Documentation/mm/ksm.rst | 87 +++ Documentation/mm/memory-model.rst | 177 ++++++ Documentation/mm/mmu_notifier.rst | 99 ++++ Documentation/mm/numa.rst | 150 ++++++ Documentation/mm/oom.rst | 5 + Documentation/mm/overcommit-accounting.rst | 88 +++ Documentation/mm/page_allocation.rst | 5 + Documentation/mm/page_cache.rst | 5 + Documentation/mm/page_frags.rst | 45 ++ Documentation/mm/page_migration.rst | 288 ++++++++++ Documentation/mm/page_owner.rst | 196 +++++++ Documentation/mm/page_reclaim.rst | 5 + Documentation/mm/page_table_check.rst | 56 ++ Documentation/mm/page_tables.rst | 5 + Documentation/mm/physical_memory.rst | 5 + Documentation/mm/process_addrs.rst | 5 + Documentation/mm/remap_file_pages.rst | 33 ++ Documentation/mm/shmfs.rst | 5 + Documentation/mm/slab.rst | 5 + Documentation/mm/slub.rst | 452 ++++++++++++++++ Documentation/mm/split_page_table_lock.rst | 100 ++++ Documentation/mm/swap.rst | 5 + Documentation/mm/transhuge.rst | 187 +++++++ Documentation/mm/unevictable-lru.rst | 554 +++++++++++++++++++ Documentation/mm/vmalloc.rst | 5 + Documentation/mm/vmalloced-kernel-stacks.rst | 153 ++++++ Documentation/mm/vmemmap_dedup.rst | 223 ++++++++ Documentation/mm/z3fold.rst | 30 ++ Documentation/mm/zsmalloc.rst | 82 +++ .../zh_CN/admin-guide/mm/damon/index.rst | 2 +- .../zh_CN/admin-guide/mm/damon/reclaim.rst | 2 +- .../zh_CN/admin-guide/mm/damon/usage.rst | 8 +- .../translations/zh_CN/core-api/index.rst | 2 +- Documentation/translations/zh_CN/index.rst | 2 +- Documentation/translations/zh_CN/mm/active_mm.rst | 85 +++ Documentation/translations/zh_CN/mm/balance.rst | 81 +++ Documentation/translations/zh_CN/mm/damon/api.rst | 32 ++ .../translations/zh_CN/mm/damon/design.rst | 140 +++++ Documentation/translations/zh_CN/mm/damon/faq.rst | 48 ++ .../translations/zh_CN/mm/damon/index.rst | 32 ++ .../translations/zh_CN/mm/free_page_reporting.rst | 38 ++ Documentation/translations/zh_CN/mm/frontswap.rst | 196 +++++++ Documentation/translations/zh_CN/mm/highmem.rst | 128 +++++ Documentation/translations/zh_CN/mm/hmm.rst | 361 +++++++++++++ .../translations/zh_CN/mm/hugetlbfs_reserv.rst | 436 +++++++++++++++ Documentation/translations/zh_CN/mm/hwpoison.rst | 166 ++++++ Documentation/translations/zh_CN/mm/index.rst | 54 ++ Documentation/translations/zh_CN/mm/ksm.rst | 70 +++ .../translations/zh_CN/mm/memory-model.rst | 135 +++++ .../translations/zh_CN/mm/mmu_notifier.rst | 97 ++++ Documentation/translations/zh_CN/mm/numa.rst | 101 ++++ .../zh_CN/mm/overcommit-accounting.rst | 86 +++ Documentation/translations/zh_CN/mm/page_frags.rst | 38 ++ Documentation/translations/zh_CN/mm/page_owner.rst | 116 ++++ .../translations/zh_CN/mm/page_table_check.rst | 56 ++ .../translations/zh_CN/mm/remap_file_pages.rst | 32 ++ .../zh_CN/mm/split_page_table_lock.rst | 96 ++++ Documentation/translations/zh_CN/mm/z3fold.rst | 31 ++ Documentation/translations/zh_CN/mm/zsmalloc.rst | 78 +++ Documentation/translations/zh_CN/vm/active_mm.rst | 85 --- Documentation/translations/zh_CN/vm/balance.rst | 81 --- Documentation/translations/zh_CN/vm/damon/api.rst | 32 -- .../translations/zh_CN/vm/damon/design.rst | 140 ----- Documentation/translations/zh_CN/vm/damon/faq.rst | 48 -- .../translations/zh_CN/vm/damon/index.rst | 33 -- .../translations/zh_CN/vm/free_page_reporting.rst | 38 -- Documentation/translations/zh_CN/vm/frontswap.rst | 196 ------- Documentation/translations/zh_CN/vm/highmem.rst | 128 ----- Documentation/translations/zh_CN/vm/hmm.rst | 361 ------------- .../translations/zh_CN/vm/hugetlbfs_reserv.rst | 436 --------------- Documentation/translations/zh_CN/vm/hwpoison.rst | 166 ------ Documentation/translations/zh_CN/vm/index.rst | 54 -- Documentation/translations/zh_CN/vm/ksm.rst | 70 --- .../translations/zh_CN/vm/memory-model.rst | 135 ----- .../translations/zh_CN/vm/mmu_notifier.rst | 97 ---- Documentation/translations/zh_CN/vm/numa.rst | 101 ---- .../zh_CN/vm/overcommit-accounting.rst | 86 --- Documentation/translations/zh_CN/vm/page_frags.rst | 38 -- Documentation/translations/zh_CN/vm/page_owner.rst | 116 ---- .../translations/zh_CN/vm/page_table_check.rst | 56 -- .../translations/zh_CN/vm/remap_file_pages.rst | 32 -- .../zh_CN/vm/split_page_table_lock.rst | 96 ---- Documentation/translations/zh_CN/vm/z3fold.rst | 31 -- Documentation/translations/zh_CN/vm/zsmalloc.rst | 78 --- Documentation/translations/zh_TW/index.rst | 2 +- Documentation/vm/.gitignore | 3 - Documentation/vm/active_mm.rst | 91 ---- Documentation/vm/arch_pgtable_helpers.rst | 260 --------- Documentation/vm/balance.rst | 102 ---- Documentation/vm/bootmem.rst | 5 - Documentation/vm/damon/api.rst | 20 - Documentation/vm/damon/design.rst | 176 ------ Documentation/vm/damon/faq.rst | 50 -- Documentation/vm/damon/index.rst | 29 - Documentation/vm/free_page_reporting.rst | 40 -- Documentation/vm/frontswap.rst | 266 --------- Documentation/vm/highmem.rst | 167 ------ Documentation/vm/hmm.rst | 452 ---------------- Documentation/vm/hugetlbfs_reserv.rst | 596 --------------------- Documentation/vm/hwpoison.rst | 184 ------- Documentation/vm/index.rst | 68 --- Documentation/vm/ksm.rst | 87 --- Documentation/vm/memory-model.rst | 177 ------ Documentation/vm/mmu_notifier.rst | 99 ---- Documentation/vm/numa.rst | 150 ------ Documentation/vm/oom.rst | 5 - Documentation/vm/overcommit-accounting.rst | 88 --- Documentation/vm/page_allocation.rst | 5 - Documentation/vm/page_cache.rst | 5 - Documentation/vm/page_frags.rst | 45 -- Documentation/vm/page_migration.rst | 288 ---------- Documentation/vm/page_owner.rst | 196 ------- Documentation/vm/page_reclaim.rst | 5 - Documentation/vm/page_table_check.rst | 56 -- Documentation/vm/page_tables.rst | 5 - Documentation/vm/physical_memory.rst | 5 - Documentation/vm/process_addrs.rst | 5 - Documentation/vm/remap_file_pages.rst | 33 -- Documentation/vm/shmfs.rst | 5 - Documentation/vm/slab.rst | 5 - Documentation/vm/slub.rst | 452 ---------------- Documentation/vm/split_page_table_lock.rst | 100 ---- Documentation/vm/swap.rst | 5 - Documentation/vm/transhuge.rst | 187 ------- Documentation/vm/unevictable-lru.rst | 554 ------------------- Documentation/vm/vmalloc.rst | 5 - Documentation/vm/vmalloced-kernel-stacks.rst | 153 ------ Documentation/vm/vmemmap_dedup.rst | 223 -------- Documentation/vm/z3fold.rst | 30 -- Documentation/vm/zsmalloc.rst | 82 --- MAINTAINERS | 12 +- arch/loongarch/Kconfig | 2 +- arch/powerpc/include/asm/book3s/64/pgtable.h | 2 +- include/linux/hmm.h | 4 +- include/linux/memremap.h | 2 +- include/linux/mmu_notifier.h | 2 +- include/linux/sched/mm.h | 4 +- include/linux/swap.h | 2 +- mm/Kconfig | 2 +- mm/debug_vm_pgtable.c | 2 +- mm/frontswap.c | 2 +- mm/huge_memory.c | 2 +- mm/hugetlb.c | 6 +- mm/hugetlb_vmemmap.c | 2 +- mm/ksm.c | 4 +- mm/mmap.c | 2 +- mm/rmap.c | 8 +- mm/sparse-vmemmap.c | 2 +- mm/util.c | 2 +- tools/vm/page_owner_sort.c | 2 +- 176 files changed, 8355 insertions(+), 8359 deletions(-) create mode 100644 Documentation/mm/active_mm.rst create mode 100644 Documentation/mm/arch_pgtable_helpers.rst create mode 100644 Documentation/mm/balance.rst create mode 100644 Documentation/mm/bootmem.rst create mode 100644 Documentation/mm/damon/api.rst create mode 100644 Documentation/mm/damon/design.rst create mode 100644 Documentation/mm/damon/faq.rst create mode 100644 Documentation/mm/damon/index.rst create mode 100644 Documentation/mm/free_page_reporting.rst create mode 100644 Documentation/mm/frontswap.rst create mode 100644 Documentation/mm/highmem.rst create mode 100644 Documentation/mm/hmm.rst create mode 100644 Documentation/mm/hugetlbfs_reserv.rst create mode 100644 Documentation/mm/hwpoison.rst create mode 100644 Documentation/mm/index.rst create mode 100644 Documentation/mm/ksm.rst create mode 100644 Documentation/mm/memory-model.rst create mode 100644 Documentation/mm/mmu_notifier.rst create mode 100644 Documentation/mm/numa.rst create mode 100644 Documentation/mm/oom.rst create mode 100644 Documentation/mm/overcommit-accounting.rst create mode 100644 Documentation/mm/page_allocation.rst create mode 100644 Documentation/mm/page_cache.rst create mode 100644 Documentation/mm/page_frags.rst create mode 100644 Documentation/mm/page_migration.rst create mode 100644 Documentation/mm/page_owner.rst create mode 100644 Documentation/mm/page_reclaim.rst create mode 100644 Documentation/mm/page_table_check.rst create mode 100644 Documentation/mm/page_tables.rst create mode 100644 Documentation/mm/physical_memory.rst create mode 100644 Documentation/mm/process_addrs.rst create mode 100644 Documentation/mm/remap_file_pages.rst create mode 100644 Documentation/mm/shmfs.rst create mode 100644 Documentation/mm/slab.rst create mode 100644 Documentation/mm/slub.rst create mode 100644 Documentation/mm/split_page_table_lock.rst create mode 100644 Documentation/mm/swap.rst create mode 100644 Documentation/mm/transhuge.rst create mode 100644 Documentation/mm/unevictable-lru.rst create mode 100644 Documentation/mm/vmalloc.rst create mode 100644 Documentation/mm/vmalloced-kernel-stacks.rst create mode 100644 Documentation/mm/vmemmap_dedup.rst create mode 100644 Documentation/mm/z3fold.rst create mode 100644 Documentation/mm/zsmalloc.rst create mode 100644 Documentation/translations/zh_CN/mm/active_mm.rst create mode 100644 Documentation/translations/zh_CN/mm/balance.rst create mode 100644 Documentation/translations/zh_CN/mm/damon/api.rst create mode 100644 Documentation/translations/zh_CN/mm/damon/design.rst create mode 100644 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Documentation/vm/shmfs.rst delete mode 100644 Documentation/vm/slab.rst delete mode 100644 Documentation/vm/slub.rst delete mode 100644 Documentation/vm/split_page_table_lock.rst delete mode 100644 Documentation/vm/swap.rst delete mode 100644 Documentation/vm/transhuge.rst delete mode 100644 Documentation/vm/unevictable-lru.rst delete mode 100644 Documentation/vm/vmalloc.rst delete mode 100644 Documentation/vm/vmalloced-kernel-stacks.rst delete mode 100644 Documentation/vm/vmemmap_dedup.rst delete mode 100644 Documentation/vm/z3fold.rst delete mode 100644 Documentation/vm/zsmalloc.rst diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm index 1c9bed5595f5..d244674a9480 100644 --- a/Documentation/ABI/testing/sysfs-kernel-mm-ksm +++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm @@ -41,7 +41,7 @@ Description: Kernel Samepage Merging daemon sysfs interface sleep_millisecs: how many milliseconds ksm should sleep between scans. - See Documentation/vm/ksm.rst for more information. + See Documentation/mm/ksm.rst for more information. What: /sys/kernel/mm/ksm/merge_across_nodes Date: January 2013 diff --git a/Documentation/ABI/testing/sysfs-kernel-slab b/Documentation/ABI/testing/sysfs-kernel-slab index c440f4946e12..cd5fb8fa3ddf 100644 --- a/Documentation/ABI/testing/sysfs-kernel-slab +++ b/Documentation/ABI/testing/sysfs-kernel-slab @@ -37,7 +37,7 @@ Description: The alloc_calls file is read-only and lists the kernel code locations from which allocations for this cache were performed. The alloc_calls file only contains information if debugging is - enabled for that cache (see Documentation/vm/slub.rst). + enabled for that cache (see Documentation/mm/slub.rst). What: /sys/kernel/slab//alloc_fastpath Date: February 2008 @@ -219,7 +219,7 @@ Contact: Pekka Enberg , Description: The free_calls file is read-only and lists the locations of object frees if slab debugging is enabled (see - Documentation/vm/slub.rst). + Documentation/mm/slub.rst). What: /sys/kernel/slab//free_fastpath Date: February 2008 diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2522b11e593f..8c0ea6b6c6a9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5442,7 +5442,7 @@ cache (risks via metadata attacks are mostly unchanged). Debug options disable merging on their own. - For more information see Documentation/vm/slub.rst. + For more information see Documentation/mm/slub.rst. slab_max_order= [MM, SLAB] Determines the maximum allowed order for slabs. @@ -5456,13 +5456,13 @@ slub_debug can create guard zones around objects and may poison objects when not in use. Also tracks the last alloc / free. For more information see - Documentation/vm/slub.rst. + Documentation/mm/slub.rst. slub_max_order= [MM, SLUB] Determines the maximum allowed order for slabs. A high setting may cause OOMs due to memory fragmentation. For more information see - Documentation/vm/slub.rst. + Documentation/mm/slub.rst. slub_min_objects= [MM, SLUB] The minimum number of objects per slab. SLUB will @@ -5471,12 +5471,12 @@ the number of objects indicated. The higher the number of objects the smaller the overhead of tracking slabs and the less frequently locks need to be acquired. - For more information see Documentation/vm/slub.rst. + For more information see Documentation/mm/slub.rst. slub_min_order= [MM, SLUB] Determines the minimum page order for slabs. Must be lower than slub_max_order. - For more information see Documentation/vm/slub.rst. + For more information see Documentation/mm/slub.rst. slub_merge [MM, SLUB] Same with slab_merge. diff --git a/Documentation/admin-guide/mm/concepts.rst b/Documentation/admin-guide/mm/concepts.rst index b966fcff993b..c79f1e336222 100644 --- a/Documentation/admin-guide/mm/concepts.rst +++ b/Documentation/admin-guide/mm/concepts.rst @@ -125,7 +125,7 @@ processor. Each bank is referred to as a `node` and for each node Linux constructs an independent memory management subsystem. A node has its own set of zones, lists of free and used pages and various statistics counters. You can find more details about NUMA in -:ref:`Documentation/vm/numa.rst ` and in +:ref:`Documentation/mm/numa.rst ` and in :ref:`Documentation/admin-guide/mm/numa_memory_policy.rst `. Page cache diff --git a/Documentation/admin-guide/mm/damon/index.rst b/Documentation/admin-guide/mm/damon/index.rst index 61aff88347f3..c4681fa69b9c 100644 --- a/Documentation/admin-guide/mm/damon/index.rst +++ b/Documentation/admin-guide/mm/damon/index.rst @@ -4,7 +4,7 @@ Monitoring Data Accesses ======================== -:doc:`DAMON ` allows light-weight data access monitoring. +:doc:`DAMON ` allows light-weight data access monitoring. Using DAMON, users can analyze the memory access patterns of their systems and optimize those. diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst index 46306f1f34b1..a8bd3bd29959 100644 --- a/Documentation/admin-guide/mm/damon/reclaim.rst +++ b/Documentation/admin-guide/mm/damon/reclaim.rst @@ -268,4 +268,4 @@ granularity reclamation. :: .. [1] https://research.google/pubs/pub48551/ .. [2] https://lwn.net/Articles/787611/ -.. [3] https://www.kernel.org/doc/html/latest/vm/free_page_reporting.html +.. [3] https://www.kernel.org/doc/html/latest/mm/free_page_reporting.html diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst index 1bb7b72414b2..5540a3a40fc9 100644 --- a/Documentation/admin-guide/mm/damon/usage.rst +++ b/Documentation/admin-guide/mm/damon/usage.rst @@ -30,11 +30,11 @@ DAMON provides below interfaces for different users. `. This will be removed after next LTS kernel is released, so users should move to the :ref:`sysfs interface `. - *Kernel Space Programming Interface.* - :doc:`This ` is for kernel space programmers. Using this, + :doc:`This ` is for kernel space programmers. Using this, users can utilize every feature of DAMON most flexibly and efficiently by writing kernel space DAMON application programs for you. You can even extend DAMON for various address spaces. For detail, please refer to the interface - :doc:`document `. + :doc:`document `. .. _sysfs_interface: @@ -185,7 +185,7 @@ controls the monitoring overhead, exist. You can set and get the values by writing to and rading from the files. For more details about the intervals and monitoring regions range, please refer -to the Design document (:doc:`/vm/damon/design`). +to the Design document (:doc:`/mm/damon/design`). contexts//targets/ --------------------- @@ -402,7 +402,7 @@ Attributes Users can get and set the ``sampling interval``, ``aggregation interval``, ``update interval``, and min/max number of monitoring target regions by reading from and writing to the ``attrs`` file. To know about the monitoring -attributes in detail, please refer to the :doc:`/vm/damon/design`. For +attributes in detail, please refer to the :doc:`/mm/damon/design`. For example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10 and 1000, and then check it again:: diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 5c9aa171a0d3..4a440a7cfeb0 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -760,7 +760,7 @@ and don't use much of it. The default value is 0. -See Documentation/vm/overcommit-accounting.rst and +See Documentation/mm/overcommit-accounting.rst and mm/util.c::__vm_enough_memory() for more information. diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index dedd4d853329..5b1188494bcd 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -87,7 +87,7 @@ Memory management ================= How to allocate and use memory in the kernel. Note that there is a lot -more memory-management documentation in Documentation/vm/index.rst. +more memory-management documentation in Documentation/mm/index.rst. .. toctree:: :maxdepth: 1 diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 1bc91fb8c321..8543a59f288f 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -1109,7 +1109,7 @@ CommitLimit yield a CommitLimit of 7.3G. For more details, see the memory overcommit documentation - in vm/overcommit-accounting. + in mm/overcommit-accounting. Committed_AS The amount of memory presently allocated on the system. The committed memory is a sum of all of the memory which diff --git a/Documentation/index.rst b/Documentation/index.rst index 67036a05b771..4737c18c97ff 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -128,7 +128,7 @@ needed). sound/index crypto/index filesystems/index - vm/index + mm/index bpf/index usb/index PCI/index diff --git a/Documentation/mm/active_mm.rst b/Documentation/mm/active_mm.rst new file mode 100644 index 000000000000..6f8269c284ed --- /dev/null +++ b/Documentation/mm/active_mm.rst @@ -0,0 +1,91 @@ +.. _active_mm: + +========= +Active MM +========= + +:: + + List: linux-kernel + Subject: Re: active_mm + From: Linus Torvalds + Date: 1999-07-30 21:36:24 + + Cc'd to linux-kernel, because I don't write explanations all that often, + and when I do I feel better about more people reading them. + + On Fri, 30 Jul 1999, David Mosberger wrote: + > + > Is there a brief description someplace on how "mm" vs. "active_mm" in + > the task_struct are supposed to be used? (My apologies if this was + > discussed on the mailing lists---I just returned from vacation and + > wasn't able to follow linux-kernel for a while). + + Basically, the new setup is: + + - we have "real address spaces" and "anonymous address spaces". The + difference is that an anonymous address space doesn't care about the + user-level page tables at all, so when we do a context switch into an + anonymous address space we just leave the previous address space + active. + + The obvious use for a "anonymous address space" is any thread that + doesn't need any user mappings - all kernel threads basically fall into + this category, but even "real" threads can temporarily say that for + some amount of time they are not going to be interested in user space, + and that the scheduler might as well try to avoid wasting time on + switching the VM state around. Currently only the old-style bdflush + sync does that. + + - "tsk->mm" points to the "real address space". For an anonymous process, + tsk->mm will be NULL, for the logical reason that an anonymous process + really doesn't _have_ a real address space at all. + + - however, we obviously need to keep track of which address space we + "stole" for such an anonymous user. For that, we have "tsk->active_mm", + which shows what the currently active address space is. + + The rule is that for a process with a real address space (ie tsk->mm is + non-NULL) the active_mm obviously always has to be the same as the real + one. + + For a anonymous process, tsk->mm == NULL, and tsk->active_mm is the + "borrowed" mm while the anonymous process is running. When the + anonymous process gets scheduled away, the borrowed address space is + returned and cleared. + + To support all that, the "struct mm_struct" now has two counters: a + "mm_users" counter that is how many "real address space users" there are, + and a "mm_count" counter that is the number of "lazy" users (ie anonymous + users) plus one if there are any real users. + + Usually there is at least one real user, but it could be that the real + user exited on another CPU while a lazy user was still active, so you do + actually get cases where you have a address space that is _only_ used by + lazy users. That is often a short-lived state, because once that thread + gets scheduled away in favour of a real thread, the "zombie" mm gets + released because "mm_count" becomes zero. + + Also, a new rule is that _nobody_ ever has "init_mm" as a real MM any + more. "init_mm" should be considered just a "lazy context when no other + context is available", and in fact it is mainly used just at bootup when + no real VM has yet been created. So code that used to check + + if (current->mm == &init_mm) + + should generally just do + + if (!current->mm) + + instead (which makes more sense anyway - the test is basically one of "do + we have a user context", and is generally done by the page fault handler + and things like that). + + Anyway, I put a pre-patch-2.3.13-1 on ftp.kernel.org just a moment ago, + because it slightly changes the interfaces to accommodate the alpha (who + would have thought it, but the alpha actually ends up having one of the + ugliest context switch codes - unlike the other architectures where the MM + and register state is separate, the alpha PALcode joins the two, and you + need to switch both together). + + (From http://marc.info/?l=linux-kernel&m=93337278602211&w=2) diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst new file mode 100644 index 000000000000..cbaee9e59241 --- /dev/null +++ b/Documentation/mm/arch_pgtable_helpers.rst @@ -0,0 +1,260 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _arch_page_table_helpers: + +=============================== +Architecture Page Table Helpers +=============================== + +Generic MM expects architectures (with MMU) to provide helpers to create, access +and modify page table entries at various level for different memory functions. +These page table helpers need to conform to a common semantics across platforms. +Following tables describe the expected semantics which can also be tested during +boot via CONFIG_DEBUG_VM_PGTABLE option. All future changes in here or the debug +test need to be in sync. + + +PTE Page Table Helpers +====================== + ++---------------------------+--------------------------------------------------+ +| pte_same | Tests whether both PTE entries are the same | ++---------------------------+--------------------------------------------------+ +| pte_bad | Tests a non-table mapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_present | Tests a valid mapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_young | Tests a young PTE | ++---------------------------+--------------------------------------------------+ +| pte_dirty | Tests a dirty PTE | ++---------------------------+--------------------------------------------------+ +| pte_write | Tests a writable PTE | ++---------------------------+--------------------------------------------------+ +| pte_special | Tests a special PTE | ++---------------------------+--------------------------------------------------+ +| pte_protnone | Tests a PROT_NONE PTE | ++---------------------------+--------------------------------------------------+ +| pte_devmap | Tests a ZONE_DEVICE mapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_soft_dirty | Tests a soft dirty PTE | ++---------------------------+--------------------------------------------------+ +| pte_swp_soft_dirty | Tests a soft dirty swapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkyoung | Creates a young PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkold | Creates an old PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkdirty | Creates a dirty PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkclean | Creates a clean PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkwrite | Creates a writable PTE | ++---------------------------+--------------------------------------------------+ +| pte_wrprotect | Creates a write protected PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkspecial | Creates a special PTE | ++---------------------------+--------------------------------------------------+ +| pte_mkdevmap | Creates a ZONE_DEVICE mapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_mksoft_dirty | Creates a soft dirty PTE | ++---------------------------+--------------------------------------------------+ +| pte_clear_soft_dirty | Clears a soft dirty PTE | ++---------------------------+--------------------------------------------------+ +| pte_swp_mksoft_dirty | Creates a soft dirty swapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_swp_clear_soft_dirty | Clears a soft dirty swapped PTE | ++---------------------------+--------------------------------------------------+ +| pte_mknotpresent | Invalidates a mapped PTE | ++---------------------------+--------------------------------------------------+ +| ptep_clear | Clears a PTE | ++---------------------------+--------------------------------------------------+ +| ptep_get_and_clear | Clears and returns PTE | ++---------------------------+--------------------------------------------------+ +| ptep_get_and_clear_full | Clears and returns PTE (batched PTE unmap) | ++---------------------------+--------------------------------------------------+ +| ptep_test_and_clear_young | Clears young from a PTE | ++---------------------------+--------------------------------------------------+ +| ptep_set_wrprotect | Converts into a write protected PTE | ++---------------------------+--------------------------------------------------+ +| ptep_set_access_flags | Converts into a more permissive PTE | ++---------------------------+--------------------------------------------------+ + + +PMD Page Table Helpers +====================== + ++---------------------------+--------------------------------------------------+ +| pmd_same | Tests whether both PMD entries are the same | ++---------------------------+--------------------------------------------------+ +| pmd_bad | Tests a non-table mapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_leaf | Tests a leaf mapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_huge | Tests a HugeTLB mapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_trans_huge | Tests a Transparent Huge Page (THP) at PMD | ++---------------------------+--------------------------------------------------+ +| pmd_present | Tests a valid mapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_young | Tests a young PMD | ++---------------------------+--------------------------------------------------+ +| pmd_dirty | Tests a dirty PMD | ++---------------------------+--------------------------------------------------+ +| pmd_write | Tests a writable PMD | ++---------------------------+--------------------------------------------------+ +| pmd_special | Tests a special PMD | ++---------------------------+--------------------------------------------------+ +| pmd_protnone | Tests a PROT_NONE PMD | ++---------------------------+--------------------------------------------------+ +| pmd_devmap | Tests a ZONE_DEVICE mapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_soft_dirty | Tests a soft dirty PMD | ++---------------------------+--------------------------------------------------+ +| pmd_swp_soft_dirty | Tests a soft dirty swapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkyoung | Creates a young PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkold | Creates an old PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkdirty | Creates a dirty PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkclean | Creates a clean PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkwrite | Creates a writable PMD | ++---------------------------+--------------------------------------------------+ +| pmd_wrprotect | Creates a write protected PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkspecial | Creates a special PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkdevmap | Creates a ZONE_DEVICE mapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mksoft_dirty | Creates a soft dirty PMD | ++---------------------------+--------------------------------------------------+ +| pmd_clear_soft_dirty | Clears a soft dirty PMD | ++---------------------------+--------------------------------------------------+ +| pmd_swp_mksoft_dirty | Creates a soft dirty swapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_swp_clear_soft_dirty | Clears a soft dirty swapped PMD | ++---------------------------+--------------------------------------------------+ +| pmd_mkinvalid | Invalidates a mapped PMD [1] | ++---------------------------+--------------------------------------------------+ +| pmd_set_huge | Creates a PMD huge mapping | ++---------------------------+--------------------------------------------------+ +| pmd_clear_huge | Clears a PMD huge mapping | ++---------------------------+--------------------------------------------------+ +| pmdp_get_and_clear | Clears a PMD | ++---------------------------+--------------------------------------------------+ +| pmdp_get_and_clear_full | Clears a PMD | ++---------------------------+--------------------------------------------------+ +| pmdp_test_and_clear_young | Clears young from a PMD | ++---------------------------+--------------------------------------------------+ +| pmdp_set_wrprotect | Converts into a write protected PMD | ++---------------------------+--------------------------------------------------+ +| pmdp_set_access_flags | Converts into a more permissive PMD | ++---------------------------+--------------------------------------------------+ + + +PUD Page Table Helpers +====================== + ++---------------------------+--------------------------------------------------+ +| pud_same | Tests whether both PUD entries are the same | ++---------------------------+--------------------------------------------------+ +| pud_bad | Tests a non-table mapped PUD | ++---------------------------+--------------------------------------------------+ +| pud_leaf | Tests a leaf mapped PUD | ++---------------------------+--------------------------------------------------+ +| pud_huge | Tests a HugeTLB mapped PUD | ++---------------------------+--------------------------------------------------+ +| pud_trans_huge | Tests a Transparent Huge Page (THP) at PUD | ++---------------------------+--------------------------------------------------+ +| pud_present | Tests a valid mapped PUD | ++---------------------------+--------------------------------------------------+ +| pud_young | Tests a young PUD | ++---------------------------+--------------------------------------------------+ +| pud_dirty | Tests a dirty PUD | ++---------------------------+--------------------------------------------------+ +| pud_write | Tests a writable PUD | ++---------------------------+--------------------------------------------------+ +| pud_devmap | Tests a ZONE_DEVICE mapped PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkyoung | Creates a young PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkold | Creates an old PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkdirty | Creates a dirty PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkclean | Creates a clean PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkwrite | Creates a writable PUD | ++---------------------------+--------------------------------------------------+ +| pud_wrprotect | Creates a write protected PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkdevmap | Creates a ZONE_DEVICE mapped PUD | ++---------------------------+--------------------------------------------------+ +| pud_mkinvalid | Invalidates a mapped PUD [1] | ++---------------------------+--------------------------------------------------+ +| pud_set_huge | Creates a PUD huge mapping | ++---------------------------+--------------------------------------------------+ +| pud_clear_huge | Clears a PUD huge mapping | ++---------------------------+--------------------------------------------------+ +| pudp_get_and_clear | Clears a PUD | ++---------------------------+--------------------------------------------------+ +| pudp_get_and_clear_full | Clears a PUD | ++---------------------------+--------------------------------------------------+ +| pudp_test_and_clear_young | Clears young from a PUD | ++---------------------------+--------------------------------------------------+ +| pudp_set_wrprotect | Converts into a write protected PUD | ++---------------------------+--------------------------------------------------+ +| pudp_set_access_flags | Converts into a more permissive PUD | ++---------------------------+--------------------------------------------------+ + + +HugeTLB Page Table Helpers +========================== + ++---------------------------+--------------------------------------------------+ +| pte_huge | Tests a HugeTLB | ++---------------------------+--------------------------------------------------+ +| pte_mkhuge | Creates a HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_pte_dirty | Tests a dirty HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_pte_write | Tests a writable HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_pte_mkdirty | Creates a dirty HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_pte_mkwrite | Creates a writable HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_pte_wrprotect | Creates a write protected HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_ptep_get_and_clear | Clears a HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_ptep_set_wrprotect | Converts into a write protected HugeTLB | ++---------------------------+--------------------------------------------------+ +| huge_ptep_set_access_flags | Converts into a more permissive HugeTLB | ++---------------------------+--------------------------------------------------+ + + +SWAP Page Table Helpers +======================== + ++---------------------------+--------------------------------------------------+ +| __pte_to_swp_entry | Creates a swapped entry (arch) from a mapped PTE | ++---------------------------+--------------------------------------------------+ +| __swp_to_pte_entry | Creates a mapped PTE from a swapped entry (arch) | ++---------------------------+--------------------------------------------------+ +| __pmd_to_swp_entry | Creates a swapped entry (arch) from a mapped PMD | ++---------------------------+--------------------------------------------------+ +| __swp_to_pmd_entry | Creates a mapped PMD from a swapped entry (arch) | ++---------------------------+--------------------------------------------------+ +| is_migration_entry | Tests a migration (read or write) swapped entry | ++-------------------------------+----------------------------------------------+ +| is_writable_migration_entry | Tests a write migration swapped entry | ++-------------------------------+----------------------------------------------+ +| make_readable_migration_entry | Creates a read migration swapped entry | ++-------------------------------+----------------------------------------------+ +| make_writable_migration_entry | Creates a write migration swapped entry | ++-------------------------------+----------------------------------------------+ + +[1] https://lore.kernel.org/linux-mm/20181017020930.GN30832@redhat.com/ diff --git a/Documentation/mm/balance.rst b/Documentation/mm/balance.rst new file mode 100644 index 000000000000..6a1fadf3e173 --- /dev/null +++ b/Documentation/mm/balance.rst @@ -0,0 +1,102 @@ +.. _balance: + +================ +Memory Balancing +================ + +Started Jan 2000 by Kanoj Sarcar + +Memory balancing is needed for !__GFP_ATOMIC and !__GFP_KSWAPD_RECLAIM as +well as for non __GFP_IO allocations. + +The first reason why a caller may avoid reclaim is that the caller can not +sleep due to holding a spinlock or is in interrupt context. The second may +be that the caller is willing to fail the allocation without incurring the +overhead of page reclaim. This may happen for opportunistic high-order +allocation requests that have order-0 fallback options. In such cases, +the caller may also wish to avoid waking kswapd. + +__GFP_IO allocation requests are made to prevent file system deadlocks. + +In the absence of non sleepable allocation requests, it seems detrimental +to be doing balancing. Page reclamation can be kicked off lazily, that +is, only when needed (aka zone free memory is 0), instead of making it +a proactive process. + +That being said, the kernel should try to fulfill requests for direct +mapped pages from the direct mapped pool, instead of falling back on +the dma pool, so as to keep the dma pool filled for dma requests (atomic +or not). A similar argument applies to highmem and direct mapped pages. +OTOH, if there is a lot of free dma pages, it is preferable to satisfy +regular memory requests by allocating one from the dma pool, instead +of incurring the overhead of regular zone balancing. + +In 2.2, memory balancing/page reclamation would kick off only when the +_total_ number of free pages fell below 1/64 th of total memory. With the +right ratio of dma and regular memory, it is quite possible that balancing +would not be done even when the dma zone was completely empty. 2.2 has +been running production machines of varying memory sizes, and seems to be +doing fine even with the presence of this problem. In 2.3, due to +HIGHMEM, this problem is aggravated. + +In 2.3, zone balancing can be done in one of two ways: depending on the +zone size (and possibly of the size of lower class zones), we can decide +at init time how many free pages we should aim for while balancing any +zone. The good part is, while balancing, we do not need to look at sizes +of lower class zones, the bad part is, we might do too frequent balancing +due to ignoring possibly lower usage in the lower class zones. Also, +with a slight change in the allocation routine, it is possible to reduce +the memclass() macro to be a simple equality. + +Another possible solution is that we balance only when the free memory +of a zone _and_ all its lower class zones falls below 1/64th of the +total memory in the zone and its lower class zones. This fixes the 2.2 +balancing problem, and stays as close to 2.2 behavior as possible. Also, +the balancing algorithm works the same way on the various architectures, +which have different numbers and types of zones. If we wanted to get +fancy, we could assign different weights to free pages in different +zones in the future. + +Note that if the size of the regular zone is huge compared to dma zone, +it becomes less significant to consider the free dma pages while +deciding whether to balance the regular zone. The first solution +becomes more attractive then. + +The appended patch implements the second solution. It also "fixes" two +problems: first, kswapd is woken up as in 2.2 on low memory conditions +for non-sleepable allocations. Second, the HIGHMEM zone is also balanced, +so as to give a fighting chance for replace_with_highmem() to get a +HIGHMEM page, as well as to ensure that HIGHMEM allocations do not +fall back into regular zone. This also makes sure that HIGHMEM pages +are not leaked (for example, in situations where a HIGHMEM page is in +the swapcache but is not being used by anyone) + +kswapd also needs to know about the zones it should balance. kswapd is +primarily needed in a situation where balancing can not be done, +probably because all allocation requests are coming from intr context +and all process contexts are sleeping. For 2.3, kswapd does not really +need to balance the highmem zone, since intr context does not request +highmem pages. kswapd looks at the zone_wake_kswapd field in the zone +structure to decide whether a zone needs balancing. + +Page stealing from process memory and shm is done if stealing the page would +alleviate memory pressure on any zone in the page's node that has fallen below +its watermark. + +watemark[WMARK_MIN/WMARK_LOW/WMARK_HIGH]/low_on_memory/zone_wake_kswapd: These +are per-zone fields, used to determine when a zone needs to be balanced. When +the number of pages falls below watermark[WMARK_MIN], the hysteric field +low_on_memory gets set. This stays set till the number of free pages becomes +watermark[WMARK_HIGH]. When low_on_memory is set, page allocation requests will +try to free some pages in the zone (providing GFP_WAIT is set in the request). +Orthogonal to this, is the decision to poke kswapd to free some zone pages. +That decision is not hysteresis based, and is done when the number of free +pages is below watermark[WMARK_LOW]; in which case zone_wake_kswapd is also set. + + +(Good) Ideas that I have heard: + +1. Dynamic experience should influence balancing: number of failed requests + for a zone can be tracked and fed into the balancing scheme (jalvo@mbay.net) +2. Implement a replace_with_highmem()-like replace_with_regular() to preserve + dma pages. (lkd@tantalophile.demon.co.uk) diff --git a/Documentation/mm/bootmem.rst b/Documentation/mm/bootmem.rst new file mode 100644 index 000000000000..eb2b31eedfa1 --- /dev/null +++ b/Documentation/mm/bootmem.rst @@ -0,0 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========== +Boot Memory +=========== diff --git a/Documentation/mm/damon/api.rst b/Documentation/mm/damon/api.rst new file mode 100644 index 000000000000..08f34df45523 --- /dev/null +++ b/Documentation/mm/damon/api.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============= +API Reference +============= + +Kernel space programs can use every feature of DAMON using below APIs. All you +need to do is including ``damon.h``, which is located in ``include/linux/`` of +the source tree. + +Structures +========== + +.. kernel-doc:: include/linux/damon.h + + +Functions +========= + +.. kernel-doc:: mm/damon/core.c diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst new file mode 100644 index 000000000000..0cff6fac6b7e --- /dev/null +++ b/Documentation/mm/damon/design.rst @@ -0,0 +1,176 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====== +Design +====== + +Configurable Layers +=================== + +DAMON provides data access monitoring functionality while making the accuracy +and the overhead controllable. The fundamental access monitorings require +primitives that dependent on and optimized for the target address space. On +the other hand, the accuracy and overhead tradeoff mechanism, which is the core +of DAMON, is in the pure logic space. DAMON separates the two parts in +different layers and defines its interface to allow various low level +primitives implementations configurable with the core logic. We call the low +level primitives implementations monitoring operations. + +Due to this separated design and the configurable interface, users can extend +DAMON for any address space by configuring the core logics with appropriate +monitoring operations. If appropriate one is not provided, users can implement +the operations on their own. + +For example, physical memory, virtual memory, swap space, those for specific +processes, NUMA nodes, files, and backing memory devices would be supportable. +Also, if some architectures or devices support special optimized access check +primitives, those will be easily configurable. + + +Reference Implementations of Address Space Specific Monitoring Operations +========================================================================= + +The monitoring operations are defined in two parts: + +1. Identification of the monitoring target address range for the address space. +2. Access check of specific address range in the target space. + +DAMON currently provides the implementations of the operations for the physical +and virtual address spaces. Below two subsections describe how those work. + + +VMA-based Target Address Range Construction +------------------------------------------- + +This is only for the virtual address space monitoring operations +implementation. That for the physical address space simply asks users to +manually set the monitoring target address ranges. + +Only small parts in the super-huge virtual address space of the processes are +mapped to the physical memory and accessed. Thus, tracking the unmapped +address regions is just wasteful. However, because DAMON can deal with some +level of noise using the adaptive regions adjustment mechanism, tracking every +mapping is not strictly required but could even incur a high overhead in some +cases. That said, too huge unmapped areas inside the monitoring target should +be removed to not take the time for the adaptive mechanism. + +For the reason, this implementation converts the complex mappings to three +distinct regions that cover every mapped area of the address space. The two +gaps between the three regions are the two biggest unmapped areas in the given +address space. The two biggest unmapped areas would be the gap between the +heap and the uppermost mmap()-ed region, and the gap between the lowermost +mmap()-ed region and the stack in most of the cases. Because these gaps are +exceptionally huge in usual address spaces, excluding these will be sufficient +to make a reasonable trade-off. Below shows this in detail:: + + + + + (small mmap()-ed regions and munmap()-ed regions) + + + + + +PTE Accessed-bit Based Access Check +----------------------------------- + +Both of the implementations for physical and virtual address spaces use PTE +Accessed-bit for basic access checks. Only one difference is the way of +finding the relevant PTE Accessed bit(s) from the address. While the +implementation for the virtual address walks the page table for the target task +of the address, the implementation for the physical address walks every page +table having a mapping to the address. In this way, the implementations find +and clear the bit(s) for next sampling target address and checks whether the +bit(s) set again after one sampling period. This could disturb other kernel +subsystems using the Accessed bits, namely Idle page tracking and the reclaim +logic. DAMON does nothing to avoid disturbing Idle page tracking, so handling +the interference is the responsibility of sysadmins. However, it solves the +conflict with the reclaim logic using ``PG_idle`` and ``PG_young`` page flags, +as Idle page tracking does. + + +Address Space Independent Core Mechanisms +========================================= + +Below four sections describe each of the DAMON core mechanisms and the five +monitoring attributes, ``sampling interval``, ``aggregation interval``, +``update interval``, ``minimum number of regions``, and ``maximum number of +regions``. + + +Access Frequency Monitoring +--------------------------- + +The output of DAMON says what pages are how frequently accessed for a given +duration. The resolution of the access frequency is controlled by setting +``sampling interval`` and ``aggregation interval``. In detail, DAMON checks +access to each page per ``sampling interval`` and aggregates the results. In +other words, counts the number of the accesses to each page. After each +``aggregation interval`` passes, DAMON calls callback functions that previously +registered by users so that users can read the aggregated results and then +clears the results. This can be described in below simple pseudo-code:: + + while monitoring_on: + for page in monitoring_target: + if accessed(page): + nr_accesses[page] += 1 + if time() % aggregation_interval == 0: + for callback in user_registered_callbacks: + callback(monitoring_target, nr_accesses) + for page in monitoring_target: + nr_accesses[page] = 0 + sleep(sampling interval) + +The monitoring overhead of this mechanism will arbitrarily increase as the +size of the target workload grows. + + +Region Based Sampling +--------------------- + +To avoid the unbounded increase of the overhead, DAMON groups adjacent pages +that assumed to have the same access frequencies into a regi