diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/memory-model.rst | 3 | ||||
| -rw-r--r-- | Documentation/vm/page_owner.rst | 12 | ||||
| -rw-r--r-- | Documentation/vm/unevictable-lru.rst | 22 |
3 files changed, 15 insertions, 22 deletions
diff --git a/Documentation/vm/memory-model.rst b/Documentation/vm/memory-model.rst index 9daadf9faba1..ce398a7dc6cd 100644 --- a/Documentation/vm/memory-model.rst +++ b/Documentation/vm/memory-model.rst @@ -51,8 +51,7 @@ call :c:func:`free_area_init` function. Yet, the mappings array is not usable until the call to :c:func:`memblock_free_all` that hands all the memory to the page allocator. -If an architecture enables `CONFIG_ARCH_HAS_HOLES_MEMORYMODEL` option, -it may free parts of the `mem_map` array that do not cover the +An architecture may free parts of the `mem_map` array that do not cover the actual physical pages. In such case, the architecture specific :c:func:`pfn_valid` implementation should take the holes in the `mem_map` into account. diff --git a/Documentation/vm/page_owner.rst b/Documentation/vm/page_owner.rst index 02deac76673f..4e67c2e9bbed 100644 --- a/Documentation/vm/page_owner.rst +++ b/Documentation/vm/page_owner.rst @@ -41,17 +41,17 @@ size change due to this facility. - Without page owner:: text data bss dec hex filename - 40662 1493 644 42799 a72f mm/page_alloc.o + 48392 2333 644 51369 c8a9 mm/page_alloc.o - With page owner:: text data bss dec hex filename - 40892 1493 644 43029 a815 mm/page_alloc.o - 1427 24 8 1459 5b3 mm/page_ext.o - 2722 50 0 2772 ad4 mm/page_owner.o + 48800 2445 644 51889 cab1 mm/page_alloc.o + 6574 108 29 6711 1a37 mm/page_owner.o + 1025 8 8 1041 411 mm/page_ext.o -Although, roughly, 4 KB code is added in total, page_alloc.o increase by -230 bytes and only half of it is in hotpath. Building the kernel with +Although, roughly, 8 KB code is added in total, page_alloc.o increase by +520 bytes and less than half of it is in hotpath. Building the kernel with page owner and turning it on if needed would be great option to debug kernel memory problem. diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst index 17d0861b0f1d..0e1490524f53 100644 --- a/Documentation/vm/unevictable-lru.rst +++ b/Documentation/vm/unevictable-lru.rst @@ -33,7 +33,7 @@ reclaim in Linux. The problems have been observed at customer sites on large memory x86_64 systems. To illustrate this with an example, a non-NUMA x86_64 platform with 128GB of -main memory will have over 32 million 4k pages in a single zone. When a large +main memory will have over 32 million 4k pages in a single node. When a large fraction of these pages are not evictable for any reason [see below], vmscan will spend a lot of time scanning the LRU lists looking for the small fraction of pages that are evictable. This can result in a situation where all CPUs are @@ -55,7 +55,7 @@ unevictable, either by definition or by circumstance, in the future. The Unevictable Page List ------------------------- -The Unevictable LRU infrastructure consists of an additional, per-zone, LRU list +The Unevictable LRU infrastructure consists of an additional, per-node, LRU list called the "unevictable" list and an associated page flag, PG_unevictable, to indicate that the page is being managed on the unevictable list. @@ -84,15 +84,9 @@ The unevictable list does not differentiate between file-backed and anonymous, swap-backed pages. This differentiation is only important while the pages are, in fact, evictable. -The unevictable list benefits from the "arrayification" of the per-zone LRU +The unevictable list benefits from the "arrayification" of the per-node LRU lists and statistics originally proposed and posted by Christoph Lameter. -The unevictable list does not use the LRU pagevec mechanism. Rather, -unevictable pages are placed directly on the page's zone's unevictable list -under the zone lru_lock. This allows us to prevent the stranding of pages on -the unevictable list when one task has the page isolated from the LRU and other -tasks are changing the "evictability" state of the page. - Memory Control Group Interaction -------------------------------- @@ -101,8 +95,8 @@ The unevictable LRU facility interacts with the memory control group [aka memory controller; see Documentation/admin-guide/cgroup-v1/memory.rst] by extending the lru_list enum. -The memory controller data structure automatically gets a per-zone unevictable -list as a result of the "arrayification" of the per-zone LRU lists (one per +The memory controller data structure automatically gets a per-node unevictable +list as a result of the "arrayification" of the per-node LRU lists (one per lru_list enum element). The memory controller tracks the movement of pages to and from the unevictable list. @@ -196,7 +190,7 @@ for the sake of expediency, to leave a unevictable page on one of the regular active/inactive LRU lists for vmscan to deal with. vmscan checks for such pages in all of the shrink_{active|inactive|page}_list() functions and will "cull" such pages that it encounters: that is, it diverts those pages to the -unevictable list for the zone being scanned. +unevictable list for the node being scanned. There may be situations where a page is mapped into a VM_LOCKED VMA, but the page is not marked as PG_mlocked. Such pages will make it all the way to @@ -328,7 +322,7 @@ If the page was NOT already mlocked, mlock_vma_page() attempts to isolate the page from the LRU, as it is likely on the appropriate active or inactive list at that time. If the isolate_lru_page() succeeds, mlock_vma_page() will put back the page - by calling putback_lru_page() - which will notice that the page -is now mlocked and divert the page to the zone's unevictable list. If +is now mlocked and divert the page to the node's unevictable list. If mlock_vma_page() is unable to isolate the page from the LRU, vmscan will handle it later if and when it attempts to reclaim the page. @@ -603,7 +597,7 @@ Some examples of these unevictable pages on the LRU lists are: unevictable list in mlock_vma_page(). shrink_inactive_list() also diverts any unevictable pages that it finds on the -inactive lists to the appropriate zone's unevictable list. +inactive lists to the appropriate node's unevictable list. shrink_inactive_list() should only see SHM_LOCK'd pages that became SHM_LOCK'd after shrink_active_list() had moved them to the inactive list, or pages mapped |