|From:||Greg Thelen <firstname.lastname@example.org>|
|To:||Andrew Morton <email@example.com>|
|Subject:||[PATCH v9 00/13] memcg: per cgroup dirty page limiting|
|Date:||Wed, 17 Aug 2011 09:14:52 -0700|
|Cc:||firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, KAMEZAWA Hiroyuki <firstname.lastname@example.org>, Balbir Singh <email@example.com>, Daisuke Nishimura <firstname.lastname@example.org>, Minchan Kim <email@example.com>, Johannes Weiner <firstname.lastname@example.org>, Wu Fengguang <email@example.com>, Dave Chinner <firstname.lastname@example.org>, Vivek Goyal <email@example.com>, Andrea Righi <firstname.lastname@example.org>, Ciju Rajan K <email@example.com>, David Rientjes <firstname.lastname@example.org>, Greg Thelen <email@example.com>|
This patch series provides the ability for each cgroup to have independent dirty page usage limits. Limiting dirty memory fixes the max amount of dirty (hard to reclaim) page cache used by a cgroup. This allows for better per cgroup memory isolation and fewer memcg OOMs. Three features are included in this patch series: 1. memcg dirty page accounting 2. memcg writeback 3. memcg dirty page limiting 1. memcg dirty page accounting Each memcg maintains a dirty page count and dirty page limit. Previous iterations of this patch series have refined this logic. The interface is similar to the procfs interface: /proc/sys/vm/dirty_*. It is possible to configure a limit to trigger throttling of a dirtier or queue background writeback. The root cgroup memory.dirty_* control files are read-only and match the contents of the /proc/sys/vm/dirty_* files. 2. memcg writeback Having per cgroup dirty memory limits is not very interesting unless writeback is also cgroup aware. There is not much isolation if cgroups have to writeback data from outside the affected cgroup to get below the cgroup dirty memory threshold. Per-memcg dirty limits are provided to support isolation and thus cross cgroup inode sharing is not a priority. This allows the code be simpler. To add cgroup awareness to writeback, this series adds an i_memcg field to struct address_space to allow writeback to isolate inodes for a particular cgroup. When an inode is marked dirty, i_memcg is set to the current cgroup. When inode pages are marked dirty the i_memcg field is compared against the page's cgroup. If they differ, then the inode is marked as shared by setting i_memcg to a special shared value (zero). When performing per-memcg writeback, move_expired_inodes() scans the per bdi b_dirty list using each inode's i_memcg and the global over-limit memcg bitmap to determine if the inode should be written. This inode scan may involve skipping many unrelated inodes from other cgroup. To test the scanning overhead, I created two cgroups (cgroup_A with 100,000 dirty inodes under A's dirty limit, cgroup_B with 1 inode over B's dirty limit). The writeback code then had to skip 100,000 inodes when balancing cgroup_B to find the one inode that needed writing. This scanning took 58 msec to skip 100,000 foreign inodes. 3. memcg dirty page limiting balance_dirty_pages() calls mem_cgroup_balance_dirty_pages(), which checks the dirty usage vs dirty thresholds for the current cgroup and its parents. As cgroups exceed their background limit, they are marked in a global over-limit bitmap (indexed by cgroup id) and the bdi flusher is awoke. As a cgroup hits is foreground limit, the task is throttled while performing foreground writeback on inodes owned by the over-limit cgroup. If mem_cgroup_balance_dirty_pages() is unable to get below the dirty page threshold writing per-memcg inodes, then downshifts to also writing shared inodes (i_memcg=0). I know that there is some significant IO-less balance_dirty_pages() changes. I am not trying to derail that effort. I have done moderate functional testing of the newly proposed features. The memcg aspects of this patch are pretty mature. The writeback aspects are still fairly new and need feedback from the writeback community. These features are linked, so it's not clear which branch to send the changes to (the writeback development branch or mmotm). Here is an example of the memcg OOM that is avoided with this patch series: # mkdir /dev/cgroup/memory/x # echo 100M > /dev/cgroup/memory/x/memory.limit_in_bytes # echo $$ > /dev/cgroup/memory/x/tasks # dd if=/dev/zero of=/data/f1 bs=1k count=1M & # dd if=/dev/zero of=/data/f2 bs=1k count=1M & # wait - Killed dd if=/dev/zero of=/data/f1 bs=1M count=1k + Killed dd if=/dev/zero of=/data/f1 bs=1M count=1k Changes since -v8: - Reordered patches for better more readability. - No longer passing struct writeback_control into memcontrol functions. Instead the needed attributes (memcg_id, etc.) are explicitly passed in. Therefore no more field additions to struct writeback_control. - Replaced 'Andrea Righi <firstname.lastname@example.org>' with 'Andrea Righi <email@example.com>' in commit descriptions. - Rebased to mmotm-2011-08-02-16-19 Greg Thelen (13): memcg: document cgroup dirty memory interfaces memcg: add page_cgroup flags for dirty page tracking memcg: add dirty page accounting infrastructure memcg: add kernel calls for memcg dirty page stats memcg: add mem_cgroup_mark_inode_dirty() memcg: add dirty limits to mem_cgroup memcg: add cgroupfs interface to memcg dirty limits memcg: dirty page accounting support routines memcg: create support routines for writeback writeback: pass wb_writeback_work into move_expired_inodes() writeback: make background writeback cgroup aware memcg: create support routines for page writeback memcg: check memcg dirty limits in page writeback Documentation/cgroups/memory.txt | 70 ++++ fs/buffer.c | 2 +- fs/fs-writeback.c | 113 ++++-- fs/inode.c | 3 + fs/nfs/write.c | 4 + fs/sync.c | 2 +- include/linux/cgroup.h | 1 + include/linux/fs.h | 9 + include/linux/memcontrol.h | 64 +++- include/linux/page_cgroup.h | 23 ++ include/linux/writeback.h | 9 +- include/trace/events/memcontrol.h | 207 ++++++++++ kernel/cgroup.c | 1 - mm/backing-dev.c | 3 +- mm/filemap.c | 1 + mm/memcontrol.c | 760 ++++++++++++++++++++++++++++++++++++- mm/page-writeback.c | 44 ++- mm/truncate.c | 1 + mm/vmscan.c | 5 +- 19 files changed, 1265 insertions(+), 57 deletions(-) create mode 100644 include/trace/events/memcontrol.h -- 188.8.131.52 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to firstname.lastname@example.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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