From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>,
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: Re: [PATCHSET v3] writeback, memcg: Implement foreign inode flushing
Date: Tue, 27 Aug 2019 09:23:09 -0600 [thread overview]
Message-ID: <15a5a6e8-90bf-726b-f68c-db91f1afc651@kernel.dk> (raw)
In-Reply-To: <20190826160656.870307-1-tj@kernel.org>
On 8/26/19 10:06 AM, Tejun Heo wrote:
> 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.
>
> Changes from v2[2]:
>
> * Added livelock avoidance and applied other smaller changes suggested
> by Jan.
>
> 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 | 130 ++++++++++++++++++++++++++++---------
> 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 | 134 +++++++++++++++++++++++++++++++++++++++
> mm/page-writeback.c | 4 +
> 8 files changed, 404 insertions(+), 53 deletions(-)
Applied for 5.4, thanks Tejun.
--
Jens Axboe
prev parent reply other threads:[~2019-08-27 15:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 16:06 [PATCHSET v3] writeback, memcg: Implement foreign inode flushing Tejun Heo
2019-08-26 16:06 ` [PATCH 1/5] writeback: Generalize and expose wb_completion Tejun Heo
2019-08-26 16:06 ` [PATCH 2/5] bdi: Add bdi->id Tejun Heo
2019-08-26 16:06 ` [PATCH 3/5] writeback: Separate out wb_get_lookup() from wb_get_create() Tejun Heo
2019-08-26 16:06 ` [PATCH 4/5] writeback, memcg: Implement cgroup_writeback_by_id() Tejun Heo
2019-08-26 16:06 ` [PATCH 5/5] writeback, memcg: Implement foreign dirty flushing Tejun Heo
2019-08-27 14:47 ` Jan Kara
2019-08-27 15:23 ` Jens Axboe [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=15a5a6e8-90bf-726b-f68c-db91f1afc651@kernel.dk \
--to=axboe@kernel.dk \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=guro@fb.com \
--cc=hannes@cmpxchg.org \
--cc=jack@suse.cz \
--cc=kernel-team@fb.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=tj@kernel.org \
--cc=vdavydov.dev@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).