diff options
Diffstat (limited to 'Documentation/mm')
| -rw-r--r-- | Documentation/mm/allocation-profiling.rst | 100 | ||||
| -rw-r--r-- | Documentation/mm/arch_pgtable_helpers.rst | 6 | ||||
| -rw-r--r-- | Documentation/mm/damon/design.rst | 44 | ||||
| -rw-r--r-- | Documentation/mm/damon/maintainer-profile.rst | 13 | ||||
| -rw-r--r-- | Documentation/mm/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/mm/page_table_check.rst | 9 | ||||
| -rw-r--r-- | Documentation/mm/transhuge.rst | 12 | ||||
| -rw-r--r-- | Documentation/mm/vmemmap_dedup.rst | 22 |
8 files changed, 153 insertions, 54 deletions
diff --git a/Documentation/mm/allocation-profiling.rst b/Documentation/mm/allocation-profiling.rst new file mode 100644 index 000000000000..d3b733b41ae6 --- /dev/null +++ b/Documentation/mm/allocation-profiling.rst @@ -0,0 +1,100 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========================== +MEMORY ALLOCATION PROFILING +=========================== + +Low overhead (suitable for production) accounting of all memory allocations, +tracked by file and line number. + +Usage: +kconfig options: +- CONFIG_MEM_ALLOC_PROFILING + +- CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT + +- CONFIG_MEM_ALLOC_PROFILING_DEBUG + adds warnings for allocations that weren't accounted because of a + missing annotation + +Boot parameter: + sysctl.vm.mem_profiling=0|1|never + + When set to "never", memory allocation profiling overhead is minimized and it + cannot be enabled at runtime (sysctl becomes read-only). + When CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=y, default value is "1". + When CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=n, default value is "never". + +sysctl: + /proc/sys/vm/mem_profiling + +Runtime info: + /proc/allocinfo + +Example output:: + + root@moria-kvm:~# sort -g /proc/allocinfo|tail|numfmt --to=iec + 2.8M 22648 fs/kernfs/dir.c:615 func:__kernfs_new_node + 3.8M 953 mm/memory.c:4214 func:alloc_anon_folio + 4.0M 1010 drivers/staging/ctagmod/ctagmod.c:20 [ctagmod] func:ctagmod_start + 4.1M 4 net/netfilter/nf_conntrack_core.c:2567 func:nf_ct_alloc_hashtable + 6.0M 1532 mm/filemap.c:1919 func:__filemap_get_folio + 8.8M 2785 kernel/fork.c:307 func:alloc_thread_stack_node + 13M 234 block/blk-mq.c:3421 func:blk_mq_alloc_rqs + 14M 3520 mm/mm_init.c:2530 func:alloc_large_system_hash + 15M 3656 mm/readahead.c:247 func:page_cache_ra_unbounded + 55M 4887 mm/slub.c:2259 func:alloc_slab_page + 122M 31168 mm/page_ext.c:270 func:alloc_page_ext + +=================== +Theory of operation +=================== + +Memory allocation profiling builds off of code tagging, which is a library for +declaring static structs (that typically describe a file and line number in +some way, hence code tagging) and then finding and operating on them at runtime, +- i.e. iterating over them to print them in debugfs/procfs. + +To add accounting for an allocation call, we replace it with a macro +invocation, alloc_hooks(), that +- declares a code tag +- stashes a pointer to it in task_struct +- calls the real allocation function +- and finally, restores the task_struct alloc tag pointer to its previous value. + +This allows for alloc_hooks() calls to be nested, with the most recent one +taking effect. This is important for allocations internal to the mm/ code that +do not properly belong to the outer allocation context and should be counted +separately: for example, slab object extension vectors, or when the slab +allocates pages from the page allocator. + +Thus, proper usage requires determining which function in an allocation call +stack should be tagged. There are many helper functions that essentially wrap +e.g. kmalloc() and do a little more work, then are called in multiple places; +we'll generally want the accounting to happen in the callers of these helpers, +not in the helpers themselves. + +To fix up a given helper, for example foo(), do the following: +- switch its allocation call to the _noprof() version, e.g. kmalloc_noprof() + +- rename it to foo_noprof() + +- define a macro version of foo() like so: + + #define foo(...) alloc_hooks(foo_noprof(__VA_ARGS__)) + +It's also possible to stash a pointer to an alloc tag in your own data structures. + +Do this when you're implementing a generic data structure that does allocations +"on behalf of" some other code - for example, the rhashtable code. This way, +instead of seeing a large line in /proc/allocinfo for rhashtable.c, we can +break it out by rhashtable type. + +To do so: +- Hook your data structure's init function, like any other allocation function. + +- Within your init function, use the convenience macro alloc_tag_record() to + record alloc tag in your data structure. + +- Then, use the following form for your allocations: + alloc_hooks_tag(ht->your_saved_tag, kmalloc_noprof(...)) diff --git a/Documentation/mm/arch_pgtable_helpers.rst b/Documentation/mm/arch_pgtable_helpers.rst index 2466d3363af7..ad50ca6f495e 100644 --- a/Documentation/mm/arch_pgtable_helpers.rst +++ b/Documentation/mm/arch_pgtable_helpers.rst @@ -140,7 +140,8 @@ PMD Page Table Helpers +---------------------------+--------------------------------------------------+ | pmd_swp_clear_soft_dirty | Clears a soft dirty swapped PMD | +---------------------------+--------------------------------------------------+ -| pmd_mkinvalid | Invalidates a mapped PMD [1] | +| pmd_mkinvalid | Invalidates a present PMD; do not call for | +| | non-present PMD [1] | +---------------------------+--------------------------------------------------+ | pmd_set_huge | Creates a PMD huge mapping | +---------------------------+--------------------------------------------------+ @@ -196,7 +197,8 @@ PUD Page Table Helpers +---------------------------+--------------------------------------------------+ | pud_mkdevmap | Creates a ZONE_DEVICE mapped PUD | +---------------------------+--------------------------------------------------+ -| pud_mkinvalid | Invalidates a mapped PUD [1] | +| pud_mkinvalid | Invalidates a present PUD; do not call for | +| | non-present PUD [1] | +---------------------------+--------------------------------------------------+ | pud_set_huge | Creates a PUD huge mapping | +---------------------------+--------------------------------------------------+ diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst index 5620aab9b385..3df387249937 100644 --- a/Documentation/mm/damon/design.rst +++ b/Documentation/mm/damon/design.rst @@ -461,24 +461,32 @@ number of filters for each scheme. Each filter specifies the type of target memory, and whether it should exclude the memory of the type (filter-out), or all except the memory of the type (filter-in). -Currently, anonymous page, memory cgroup, address range, and DAMON monitoring -target type filters are supported by the feature. Some filter target types -require additional arguments. The memory cgroup filter type asks users to -specify the file path of the memory cgroup for the filter. The address range -type asks the start and end addresses of the range. The DAMON monitoring -target type asks the index of the target from the context's monitoring targets -list. Hence, users can apply specific schemes to only anonymous pages, -non-anonymous pages, pages of specific cgroups, all pages excluding those of -specific cgroups, pages in specific address range, pages in specific DAMON -monitoring targets, and any combination of those. - -To handle filters efficiently, the address range and DAMON monitoring target -type filters are handled by the core layer, while others are handled by -operations set. If a memory region is filtered by a core layer-handled filter, -it is not counted as the scheme has tried to the region. In contrast, if a -memory regions is filtered by an operations set layer-handled filter, it is -counted as the scheme has tried. The difference in accounting leads to changes -in the statistics. +For efficient handling of filters, some types of filters are handled by the +core layer, while others are handled by operations set. In the latter case, +hence, support of the filter types depends on the DAMON operations set. In +case of the core layer-handled filters, the memory regions that excluded by the +filter are not counted as the scheme has tried to the region. In contrast, if +a memory regions is filtered by an operations set layer-handled filter, it is +counted as the scheme has tried. This difference affects the statistics. + +Below types of filters are currently supported. + +- anonymous page + - Applied to pages that containing data that not stored in files. + - Handled by operations set layer. Supported by only ``paddr`` set. +- memory cgroup + - Applied to pages that belonging to a given cgroup. + - Handled by operations set layer. Supported by only ``paddr`` set. +- young page + - Applied to pages that are accessed after the last access check from the + scheme. + - Handled by operations set layer. Supported by only ``paddr`` set. +- address range + - Applied to pages that belonging to a given address range. + - Handled by the core logic. +- DAMON monitoring target + - Applied to pages that belonging to a given DAMON monitoring target. + - Handled by the core logic. Application Programming Interface diff --git a/Documentation/mm/damon/maintainer-profile.rst b/Documentation/mm/damon/maintainer-profile.rst index 5a306e4de22e..8213cf61d38a 100644 --- a/Documentation/mm/damon/maintainer-profile.rst +++ b/Documentation/mm/damon/maintainer-profile.rst @@ -20,9 +20,10 @@ management subsystem maintainer. After more sufficient tests, the patches will be queued in mm-stable [3]_ , and finally pull-requested to the mainline by the memory management subsystem maintainer. -Note again the patches for review should be made against the mm-unstable -tree [1]_ whenever possible. damon/next is only for preview of others' works -in progress. +Note again the patches for mm-unstable tree [1]_ are queued by the memory +management subsystem maintainer. If the patches requires some patches in +damon/next tree [2]_ which not yet merged in mm-unstable, please make sure the +requirement is clearly specified. Submit checklist addendum ------------------------- @@ -48,9 +49,9 @@ Review cadence -------------- The DAMON maintainer does the work on the usual work hour (09:00 to 17:00, -Mon-Fri) in PST. The response to patches will occasionally be slow. Do not -hesitate to send a ping if you have not heard back within a week of sending a -patch. +Mon-Fri) in PT (Pacific Time). The response to patches will occasionally be +slow. Do not hesitate to send a ping if you have not heard back within a week +of sending a patch. .. [1] https://git.kernel.org/akpm/mm/h/mm-unstable diff --git a/Documentation/mm/index.rst b/Documentation/mm/index.rst index 31d2ac306438..48b9b559ca7b 100644 --- a/Documentation/mm/index.rst +++ b/Documentation/mm/index.rst @@ -26,6 +26,7 @@ see the :doc:`admin guide <../admin-guide/mm/index>`. page_cache shmfs oom + allocation-profiling Legacy Documentation ==================== diff --git a/Documentation/mm/page_table_check.rst b/Documentation/mm/page_table_check.rst index c12838ce6b8d..c59f22eb6a0f 100644 --- a/Documentation/mm/page_table_check.rst +++ b/Documentation/mm/page_table_check.rst @@ -14,7 +14,7 @@ Page table check performs extra verifications at the time when new pages become accessible from the userspace by getting their page table entries (PTEs PMDs etc.) added into the table. -In case of detected corruption, the kernel is crashed. There is a small +In case of most detected corruption, the kernel is crashed. There is a small performance and memory overhead associated with the page table check. Therefore, it is disabled by default, but can be optionally enabled on systems where the extra hardening outweighs the performance costs. Also, because page table check @@ -22,6 +22,13 @@ is synchronous, it can help with debugging double map memory corruption issues, by crashing kernel at the time wrong mapping occurs instead of later which is often the case with memory corruptions bugs. +It can also be used to do page table entry checks over various flags, dump +warnings when illegal combinations of entry flags are detected. Currently, +userfaultfd is the only user of such to sanity check wr-protect bit against +any writable flags. Illegal flag combinations will not directly cause data +corruption in this case immediately, but that will cause read-only data to +be writable, leading to corrupt when the page content is later modified. + Double mapping detection logic ============================== diff --git a/Documentation/mm/transhuge.rst b/Documentation/mm/transhuge.rst index 93c9239b9ebe..1ba0ad63246c 100644 --- a/Documentation/mm/transhuge.rst +++ b/Documentation/mm/transhuge.rst @@ -116,14 +116,14 @@ pages: succeeds on tail pages. - map/unmap of a PMD entry for the whole THP increment/decrement - folio->_entire_mapcount and also increment/decrement - folio->_nr_pages_mapped by ENTIRELY_MAPPED when _entire_mapcount - goes from -1 to 0 or 0 to -1. + folio->_entire_mapcount, increment/decrement folio->_large_mapcount + and also increment/decrement folio->_nr_pages_mapped by ENTIRELY_MAPPED + when _entire_mapcount goes from -1 to 0 or 0 to -1. - map/unmap of individual pages with PTE entry increment/decrement - page->_mapcount and also increment/decrement folio->_nr_pages_mapped - when page->_mapcount goes from -1 to 0 or 0 to -1 as this counts - the number of pages mapped by PTE. + page->_mapcount, increment/decrement folio->_large_mapcount and also + increment/decrement folio->_nr_pages_mapped when page->_mapcount goes + from -1 to 0 or 0 to -1 as this counts the number of pages mapped by PTE. split_huge_page internally has to distribute the refcounts in the head page to the tail pages before clearing all PG_head/tail bits from the page diff --git a/Documentation/mm/vmemmap_dedup.rst b/Documentation/mm/vmemmap_dedup.rst index 593ede6d314b..b4a55b6569fa 100644 --- a/Documentation/mm/vmemmap_dedup.rst +++ b/Documentation/mm/vmemmap_dedup.rst @@ -180,27 +180,7 @@ this correctly. There is only **one** head ``struct page``, the tail ``struct page`` with ``PG_head`` are fake head ``struct page``. We need an approach to distinguish between those two different types of ``struct page`` so that ``compound_head()`` can return the real head ``struct page`` when the -parameter is the tail ``struct page`` but with ``PG_head``. The following code -snippet describes how to distinguish between real and fake head ``struct page``. - -.. code-block:: c - - if (test_bit(PG_head, &page->flags)) { - unsigned long head = READ_ONCE(page[1].compound_head); - - if (head & 1) { - if (head == (unsigned long)page + 1) - /* head struct page */ - else - /* tail struct page */ - } else { - /* head struct page */ - } - } - -We can safely access the field of the **page[1]** with ``PG_head`` because the -page is a compound page composed with at least two contiguous pages. -The implementation refers to ``page_fixed_fake_head()``. +parameter is the tail ``struct page`` but with ``PG_head``. Device DAX ========== |