Message-ID: <49F01E8F.80807@cn.fujitsu.com>
Date: Thu, 23 Apr 2009 15:53:51 +0800
From: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
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To: Andrea Righi <righi.andrea@gmail.com>
CC: Paul Menage <menage@google.com>, Balbir Singh <balbir@linux.vnet.ibm.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, agk@sourceware.org,
       akpm@linux-foundation.org, axboe@kernel.dk, baramsori72@gmail.com,
       Carl Henrik Lunde <chlunde@ping.uio.no>, dave@linux.vnet.ibm.com,
       Divyesh Shah <dpshah@google.com>, eric.rannaud@gmail.com,
       fernando@oss.ntt.co.jp, Hirokazu Takahashi <taka@valinux.co.jp>,
       Li Zefan <lizf@cn.fujitsu.com>, matt@bluehost.com,
       dradford@bluehost.com, ngupta@google.com, randy.dunlap@oracle.com,
       roberto@unbit.it, Ryo Tsuruta <ryov@valinux.co.jp>,
       Satoshi UCHIDA <s-uchida@ap.jp.nec.com>, subrata@linux.vnet.ibm.com,
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       fchecconi@gmail.com, paolo.valente@unimore.it,
       containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/7] kiothrottled: throttle buffered (writeback) IO
References: <1240090712-1058-1-git-send-email-righi.andrea@gmail.com> <1240090712-1058-6-git-send-email-righi.andrea@gmail.com>
In-Reply-To: <1240090712-1058-6-git-send-email-righi.andrea@gmail.com>
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Andrea Righi wrote:
> Together with cgroup_io_throttle() the kiothrottled kernel thread
> represents the core of the io-throttle subsystem.
> 
> All the writeback IO requests that need to be throttled are not
> dispatched immediately in submit_bio(). Instead, they are added into an
> rbtree by iothrottle_make_request() and processed asynchronously by
> kiothrottled.
> 
> A deadline is associated to each request depending on the bandwidth
> usage of the cgroup it belongs. When a request is inserted into the
> rbtree kiothrottled is awakened. This thread selects all the requests
> with an expired deadline and submit the bunch of selected requests to
> the underlying block devices using generic_make_request().

  Hi Andrea,

  What if an user issues "sync", will the bios still be buffered in the rb-tree?
  Do we need to flush the whole tree?

-- 
Regards
Gui Jianfeng

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