From: Vivek Goyal <vgoyal@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>,
containers@lists.linux-foundation.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, fweisbec@gmail.com, rni@google.com,
ctalbott@google.com, Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>,
Balbir Singh <bsingharora@gmail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCH 2/2] cgroup: make css->refcnt clearing on cgroup removal optional
Date: Sun, 1 Apr 2012 15:48:23 -0400 [thread overview]
Message-ID: <20120401194823.GB6116@redhat.com> (raw)
In-Reply-To: <20120330223606.GK28934@google.com>
On Fri, Mar 30, 2012 at 03:36:06PM -0700, Tejun Heo wrote:
> Currently, cgroup removal tries to drain all css references. If there
> are active css references, the removal logic waits and retries
> ->pre_detroy() until either all refs drop to zero or removal is
> cancelled.
>
> This semantics is unusual and adds non-trivial complexity to cgroup
> core and IMHO is fundamentally misguided in that it couples internal
> implementation details (references to internal data structure) with
> externally visible operation (rmdir). To userland, this is a behavior
> peculiarity which is unnecessary and difficult to expect (css refs is
> otherwise invisible from userland), and, to policy implementations,
> this is an unnecessary restriction (e.g. blkcg wants to hold css refs
> for caching purposes but can't as that becomes visible as rmdir hang).
Good to see this patch. Now annyoying rmdir hang with blkcg should be
gone.
Thanks
Vivek
prev parent reply other threads:[~2012-04-01 19:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-30 22:34 [PATCH 1/2] cgroup: use negative bias on css->refcnt to block css_tryget() Tejun Heo
2012-03-30 22:36 ` [PATCH 2/2] cgroup: make css->refcnt clearing on cgroup removal optional Tejun Heo
2012-03-31 21:28 ` Hiroyuki Kamezawa
2012-04-01 2:00 ` Li Zefan
2012-04-01 18:54 ` Tejun Heo
2012-05-16 22:33 ` Sasha Levin
2012-05-18 17:55 ` Tejun Heo
2012-05-18 18:28 ` Sasha Levin
2012-05-23 22:22 ` Tejun Heo
2012-05-24 13:21 ` Sasha Levin
2012-05-24 15:41 ` [PATCH] cgroup: superblock can't be released with active dentries Tejun Heo
2012-05-28 0:18 ` Li Zefan
2012-04-01 19:48 ` Vivek Goyal [this message]
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