From: Tejun Heo <tj@kernel.org>
To: axboe@kernel.dk, jack@suse.cz, hannes@cmpxchg.org,
mhocko@kernel.org, vdavydov.dev@gmail.com
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, guro@fb.com, akpm@linux-foundation.org
Subject: [PATCHSET] writeback, memcg: Implement foreign inode flushing
Date: Sat, 3 Aug 2019 07:01:51 -0700 [thread overview]
Message-ID: <20190803140155.181190-1-tj@kernel.org> (raw)
Hello,
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-memcg-Implement-cgroup_writeback_by_id.patch
0004-writeback-memcg-Implement-foreign-dirty-flushing.patch
0001-0003 are prep patches which expose wb_completion and implement
bdi->id and flushing by bdi and memcg IDs.
0004 implement foreign inode flushing.
Thanks. diffstat follows.
fs/fs-writeback.c | 111 ++++++++++++++++++++++++----------
include/linux/backing-dev-defs.h | 23 +++++++
include/linux/backing-dev.h | 3
include/linux/memcontrol.h | 35 ++++++++++
include/linux/writeback.h | 4 +
mm/backing-dev.c | 65 +++++++++++++++++++-
mm/memcontrol.c | 125 +++++++++++++++++++++++++++++++++++++++
mm/page-writeback.c | 4 +
8 files changed, 335 insertions(+), 35 deletions(-)
--
tejun
next reply other threads:[~2019-08-03 14:02 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-03 14:01 Tejun Heo [this message]
2019-08-03 14:01 ` [PATCH 1/4] writeback: Generalize and expose wb_completion Tejun Heo
2019-08-15 14:41 ` Jan Kara
2019-08-03 14:01 ` [PATCH 2/4] bdi: Add bdi->id Tejun Heo
2019-08-03 15:39 ` Matthew Wilcox
2019-08-03 15:53 ` Tejun Heo
2019-08-03 16:17 ` Matthew Wilcox
2019-08-06 23:01 ` Andrew Morton
2019-08-07 18:31 ` Tejun Heo
2019-08-07 19:00 ` Andrew Morton
2019-08-07 20:34 ` Tejun Heo
2019-08-09 0:57 ` Rik van Riel
2019-08-15 14:46 ` Jan Kara
2019-08-15 17:34 ` Tejun Heo
2019-08-03 14:01 ` [PATCH 3/4] writeback, memcg: Implement cgroup_writeback_by_id() Tejun Heo
2019-08-15 14:05 ` Jan Kara
2019-08-15 15:43 ` Tejun Heo
2019-08-15 14:54 ` Jan Kara
2019-08-15 16:12 ` Tejun Heo
2019-08-03 14:01 ` [PATCH 4/4] writeback, memcg: Implement foreign dirty flushing Tejun Heo
2019-08-06 23:03 ` Andrew Morton
2019-08-07 18:34 ` Tejun Heo
2019-08-15 14:34 ` Jan Kara
2019-08-15 17:31 ` Tejun Heo
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