Hello, Changes from v1[1]: * More comments explaining the parameters. * 0003-writeback-Separate-out-wb_get_lookup-from-wb_get_create.patch added and avoid spuriously creating missing wbs for foreign flushing. There's an inherent mismatch between memcg and writeback. The former trackes ownership per-page while the latter per-inode. This was a deliberate design decision because honoring per-page ownership in the writeback path is complicated, may lead to higher CPU and IO overheads and deemed unnecessary given that write-sharing an inode across different cgroups isn't a common use-case. Combined with inode majority-writer ownership switching, this works well enough in most cases but there are some pathological cases. For example, let's say there are two cgroups A and B which keep writing to different but confined parts of the same inode. B owns the inode and A's memory is limited far below B's. A's dirty ratio can rise enough to trigger balance_dirty_pages() sleeps but B's can be low enough to avoid triggering background writeback. A will be slowed down without a way to make writeback of the dirty pages happen. This patchset implements foreign dirty recording and foreign mechanism so that when a memcg encounters a condition as above it can trigger flushes on bdi_writebacks which can clean its pages. Please see the last patch for more details. This patchset contains the following four patches. 0001-writeback-Generalize-and-expose-wb_completion.patch 0002-bdi-Add-bdi-id.patch 0003-writeback-Separate-out-wb_get_lookup-from-wb_get_create.patch 0004-writeback-memcg-Implement-cgroup_writeback_by_id.patch 0005-writeback-memcg-Implement-foreign-dirty-flushing.patch 0001-0004 are prep patches which expose wb_completion and implement bdi->id and flushing by bdi and memcg IDs. 0005 implements foreign inode flushing. Thanks. diffstat follows. fs/fs-writeback.c | 114 +++++++++++++++++++++++---------- include/linux/backing-dev-defs.h | 23 ++++++ include/linux/backing-dev.h | 5 + include/linux/memcontrol.h | 39 +++++++++++ include/linux/writeback.h | 2 mm/backing-dev.c | 120 +++++++++++++++++++++++++++++------ mm/memcontrol.c | 132 +++++++++++++++++++++++++++++++++++++++ mm/page-writeback.c | 4 + 8 files changed, 386 insertions(+), 53 deletions(-) -- tejun [1] http://lkml.kernel.org/r/20190803140155.181190-1-tj@xxxxxxxxxx
