From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> Subject: mm: memcontrol: document the new swap control behavior Link: http://lkml.kernel.org/r/20200508183105.225460-18-hannes@xxxxxxxxxxx Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Roman Gushchin <guro@xxxxxx> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Balbir Singh <bsingharora@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/cgroup-v1/memory.rst | 19 +++++---------- 1 file changed, 7 insertions(+), 12 deletions(-) --- a/Documentation/admin-guide/cgroup-v1/memory.rst~mm-memcontrol-document-the-new-swap-control-behavior +++ a/Documentation/admin-guide/cgroup-v1/memory.rst @@ -199,11 +199,11 @@ An RSS page is unaccounted when it's ful unaccounted when it's removed from radix-tree. Even if RSS pages are fully unmapped (by kswapd), they may exist as SwapCache in the system until they are really freed. Such SwapCaches are also accounted. -A swapped-in page is not accounted until it's mapped. +A swapped-in page is accounted after adding into swapcache. Note: The kernel does swapin-readahead and reads multiple swaps at once. -This means swapped-in pages may contain pages for other tasks than a task -causing page fault. So, we avoid accounting at swap-in I/O. +Since page's memcg recorded into swap whatever memsw enabled, the page will +be accounted after swapin. At page migration, accounting information is kept. @@ -222,18 +222,13 @@ the cgroup that brought it in -- this wi But see section 8.2: when moving a task to another cgroup, its pages may be recharged to the new cgroup, if move_charge_at_immigrate has been chosen. -Exception: If CONFIG_MEMCG_SWAP is not used. -When you do swapoff and make swapped-out pages of shmem(tmpfs) to -be backed into memory in force, charges for pages are accounted against the -caller of swapoff rather than the users of shmem. - -2.4 Swap Extension (CONFIG_MEMCG_SWAP) +2.4 Swap Extension -------------------------------------- -Swap Extension allows you to record charge for swap. A swapped-in page is -charged back to original page allocator if possible. +Swap usage is always recorded for each of cgroup. Swap Extension allows you to +read and limit it. -When swap is accounted, following files are added. +When CONFIG_SWAP is enabled, following files are added. - memory.memsw.usage_in_bytes. - memory.memsw.limit_in_bytes. _
