linux-kernel - Re: [RFC] [PATCH 0/6] Provide cgroup isolation for buffered writes.

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Date:	Tue, 8 Mar 2011 17:50:59 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Justin TerAvest <teravest@...gle.com>
Cc:	m-ikeda@...jp.nec.com, jaxboe@...ionio.com,
	linux-kernel@...r.kernel.org, ryov@...inux.co.jp,
	taka@...inux.co.jp, kamezawa.hiroyu@...fujitsu.com,
	righi.andrea@...il.com, guijianfeng@...fujitsu.com,
	balbir@...ux.vnet.ibm.com, ctalbott@...gle.com, nauman@...gle.com,
	mrubin@...gle.com
Subject: Re: [RFC] [PATCH 0/6] Provide cgroup isolation for buffered writes.

On Tue, Mar 08, 2011 at 05:43:25PM -0500, Vivek Goyal wrote:
> On Tue, Mar 08, 2011 at 01:20:50PM -0800, Justin TerAvest wrote:
> > This patchset adds tracking to the page_cgroup structure for which cgroup has
> > dirtied a page, and uses that information to provide isolation between
> > cgroups performing writeback.
> > 
> 
> Justin,
> 
> So if somebody is trying to isolate a workload which does bunch of READS
> and lots of buffered WRITES, this patchset should help in the sense that
> all the heavy WRITES can be put into a separate cgroup of low weight?
> 
> Other application which are primarily doing READS, direct WRITES or little
> bit of buffered WRITES should still get good latencies if heavy writer
> is isolated in a separate group?
> 
> If yes, then this piece standalone can make sense. And once the other
> piece/patches of memory cgroup dirty ratio and cgroup aware buffered
> writeout come in, then one will be able to differentiate buffered writes
> of different groups.

Thinking more about it, currently anyway SYNC preempts the ASYNC. So the
question would be will it help me enable get better isolation latencies
of READS agains buffered WRITES?

Thanks
Vivek 

> 
> Thanks
> Vivek
> 
> > I know that there is some discussion to remove request descriptor limits
> > entirely, but I included a patch to introduce per-cgroup limits to enable
> > this functionality. Without it, we didn't see much isolation improvement.
> > 
> > I think most of this material has been discussed on lkml previously, this is
> > just another attempt to make a patchset that handles buffered writes for CFQ.
> > 
> > There was a lot of previous discussion at:
> >   http://thread.gmane.org/gmane.linux.kernel/1007922
> > 
> > Thanks to Andrea Righi, Kamezawa Hiroyuki, Munehiro Ikeda, Nauman Rafique,
> > and Vivek Goyal for work on previous versions of these patches.
> > 
> > 
> >  Documentation/block/biodoc.txt |   10 +
> >  block/blk-cgroup.c             |  204 +++++++++++++++++++++-
> >  block/blk-cgroup.h             |    9 +-
> >  block/blk-core.c               |  216 +++++++++++++++--------
> >  block/blk-settings.c           |    2 +-
> >  block/blk-sysfs.c              |   60 ++++---
> >  block/cfq-iosched.c            |  390 +++++++++++++++++++++++++++++++---------
> >  block/cfq.h                    |    6 +-
> >  block/elevator.c               |   11 +-
> >  fs/buffer.c                    |    2 +
> >  fs/direct-io.c                 |    2 +
> >  include/linux/blk_types.h      |    2 +
> >  include/linux/blkdev.h         |   81 ++++++++-
> >  include/linux/blkio-track.h    |   89 +++++++++
> >  include/linux/elevator.h       |   14 ++-
> >  include/linux/iocontext.h      |    1 +
> >  include/linux/memcontrol.h     |    6 +
> >  include/linux/mmzone.h         |    4 +-
> >  include/linux/page_cgroup.h    |   12 +-
> >  init/Kconfig                   |   16 ++
> >  mm/Makefile                    |    3 +-
> >  mm/bounce.c                    |    2 +
> >  mm/filemap.c                   |    2 +
> >  mm/memcontrol.c                |    6 +
> >  mm/memory.c                    |    6 +
> >  mm/page-writeback.c            |   14 ++-
> >  mm/page_cgroup.c               |   29 ++-
> >  mm/swap_state.c                |    2 +
> >  28 files changed, 985 insertions(+), 216 deletions(-)
> > 
> > [PATCH 1/6] Add IO cgroup tracking for buffered writes.
> > [PATCH 2/6] Make async queues per cgroup.
> > [PATCH 3/6] Modify CFQ to use IO tracking information.
> > [PATCH 4/6] With per-cgroup async, don't special case queues.
> > [PATCH 5/6] Add stat for per cgroup writeout done by flusher.
> > [PATCH 6/6] Per cgroup request descriptor counts
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