linux-kernel - Re: [PATCH 3/5] page_cgroup: make page tracking available for blkio

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Date:	Wed, 23 Feb 2011 00:08:40 +0100
From:	Andrea Righi <arighi@...eler.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Greg Thelen <gthelen@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Gui Jianfeng <guijianfeng@...fujitsu.com>,
	Ryo Tsuruta <ryov@...inux.co.jp>,
	Hirokazu Takahashi <taka@...inux.co.jp>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	containers@...ts.linux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] page_cgroup: make page tracking available for blkio

On Tue, Feb 22, 2011 at 04:22:53PM -0500, Vivek Goyal wrote:
> On Tue, Feb 22, 2011 at 06:12:54PM +0100, Andrea Righi wrote:
> > The page_cgroup infrastructure, currently available only for the memory
> > cgroup controller, can be used to store the owner of each page and
> > opportunely track the writeback IO. This information is encoded in
> > the upper 16-bits of the page_cgroup->flags.
> > 
> > A owner can be identified using a generic ID number and the following
> > interfaces are provided to store a retrieve this information:
> > 
> >   unsigned long page_cgroup_get_owner(struct page *page);
> >   int page_cgroup_set_owner(struct page *page, unsigned long id);
> >   int page_cgroup_copy_owner(struct page *npage, struct page *opage);
> > 
> > The blkio.throttle controller can use the cgroup css_id() as the owner's
> > ID number.
> > 
> > Signed-off-by: Andrea Righi <arighi@...eler.com>
> > ---
> >  block/Kconfig               |    2 +
> >  block/blk-cgroup.c          |    6 ++
> >  include/linux/memcontrol.h  |    6 ++
> >  include/linux/mmzone.h      |    4 +-
> >  include/linux/page_cgroup.h |   33 ++++++++++-
> >  init/Kconfig                |    4 +
> >  mm/Makefile                 |    3 +-
> >  mm/memcontrol.c             |    6 ++
> >  mm/page_cgroup.c            |  129 +++++++++++++++++++++++++++++++++++++++----
> >  9 files changed, 176 insertions(+), 17 deletions(-)
> > 
> > diff --git a/block/Kconfig b/block/Kconfig
> > index 60be1e0..1351ea8 100644
> > --- a/block/Kconfig
> > +++ b/block/Kconfig
> > @@ -80,6 +80,8 @@ config BLK_DEV_INTEGRITY
> >  config BLK_DEV_THROTTLING
> >  	bool "Block layer bio throttling support"
> >  	depends on BLK_CGROUP=y && EXPERIMENTAL
> > +	select MM_OWNER
> > +	select PAGE_TRACKING
> >  	default n
> >  	---help---
> >  	Block layer bio throttling support. It can be used to limit
> > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> > index f283ae1..5c57f0a 100644
> > --- a/block/blk-cgroup.c
> > +++ b/block/blk-cgroup.c
> > @@ -107,6 +107,12 @@ blkio_policy_search_node(const struct blkio_cgroup *blkcg, dev_t dev,
> >  	return NULL;
> >  }
> >  
> > +bool blkio_cgroup_disabled(void)
> > +{
> > +	return blkio_subsys.disabled ? true : false;
> > +}
> > +EXPORT_SYMBOL_GPL(blkio_cgroup_disabled);
> > +
> 
> I think there should be option to just disable this asyn feature of
> blkio controller. So those who don't want it (running VMs with cache=none
> option) and don't want to take the memory reservation hit should be
> able to disable just ASYNC facility of blkio controller and not
> the whole blkio controller facility.

Definitely a better choice.

OK, I'll apply all your suggestions and post a new version of the patch.

Thanks for the review!
-Andrea
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