From: Lennart Poettering <mzxreary@0pointer.de>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Tejun Heo <tj@kernel.org>,
axboe@kernel.dk, ctalbott@google.com, rni@google.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/17] blkcg: shoot down blkio_groups on elevator switch
Date: Mon, 23 Jan 2012 21:40:17 +0100 [thread overview]
Message-ID: <20120123204016.GA21822@tango.0pointer.de> (raw)
In-Reply-To: <20120123182745.GK25986@redhat.com>
On Mon, 23.01.12 13:27, Vivek Goyal (vgoyal@redhat.com) wrote:
> > Why can't systemd order elevator switch before other actions?
>
> Because systemd does not know. For systemd it is just launching services
> and what services are doing is not known to systemd.
>
> I think systemd does have some facilities so that services can express
> dependency on other services and dependent service blocks on completion
> of service it is depenent on. So may be in this case any service dealing
> with cgroups shall have to be dependent on this service which tunes
> the system and changes elevator.
>
> CCing lennart for more info on systemd.
Yes, the dependency logic is quite elaborate in systemd. If a service
really needs to it can plug itself into the early-boot phase, instead of
normal boot. It's where we usually load drivers via udev and apply
sysctl and these things, hence before any of the "real" services. So far
only udev itself (and plymouth in some way) are of this special kind
that run this early, but other services may move themselves this
early as well, if they want to.
Note that sticking code in the early boot phase means you need to know
what you do, i.e. not rely on device nodes being there, drivers probed,
access modes fixed, temporary files set up and so on, after all it's
where we do all those things in the first place. You can order yourself
individually after those tasks however, if needed.
Lennart
--
Lennart Poettering - Red Hat, Inc.
next prev parent reply other threads:[~2012-01-23 20:40 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-22 3:25 [PATCHSET] blkcg: kill policy node and blkg->dev, take#2 Tejun Heo
2012-01-22 3:25 ` [PATCH 01/17] blkcg: make CONFIG_BLK_CGROUP bool Tejun Heo
2012-01-23 15:00 ` Vivek Goyal
2012-01-23 15:34 ` Tejun Heo
2012-01-22 3:25 ` [PATCH 02/17] cfq: don't register propio policy if !CONFIG_CFQ_GROUP_IOSCHED Tejun Heo
2012-01-22 3:25 ` [PATCH 03/17] elevator: clear auxiliary data earlier during elevator switch Tejun Heo
2012-01-22 3:25 ` [PATCH 04/17] elevator: make elevator_init_fn() return 0/-errno Tejun Heo
2012-01-22 3:25 ` [PATCH 05/17] block: implement blk_queue_bypass_start/end() Tejun Heo
2012-01-22 3:25 ` [PATCH 06/17] block: extend queue bypassing to cover blkcg policies Tejun Heo
2012-01-22 3:25 ` [PATCH 07/17] blkcg: make blkio_list_lock irq-safe Tejun Heo
2012-01-22 3:25 ` [PATCH 08/17] blkcg: shoot down blkio_groups on elevator switch Tejun Heo
2012-01-23 15:20 ` Vivek Goyal
2012-01-23 15:36 ` Vivek Goyal
2012-01-23 15:49 ` Tejun Heo
2012-01-23 15:39 ` Tejun Heo
2012-01-23 15:52 ` Vivek Goyal
2012-01-23 15:57 ` Tejun Heo
2012-01-23 16:10 ` Vivek Goyal
2012-01-23 16:13 ` Vivek Goyal
2012-01-23 16:20 ` Tejun Heo
2012-01-23 16:28 ` Vivek Goyal
2012-01-23 16:32 ` Tejun Heo
2012-01-23 16:16 ` Tejun Heo
2012-01-23 16:25 ` Vivek Goyal
2012-01-23 17:10 ` Tejun Heo
2012-01-23 18:27 ` Vivek Goyal
2012-01-23 18:43 ` Tejun Heo
2012-01-23 19:33 ` Tejun Heo
2012-01-23 19:57 ` Vivek Goyal
2012-01-23 20:33 ` Tejun Heo
2012-01-23 20:43 ` Lennart Poettering
2012-01-23 20:47 ` Tejun Heo
2012-01-23 21:03 ` Vivek Goyal
2012-01-23 20:40 ` Lennart Poettering [this message]
2012-01-23 18:32 ` Vivek Goyal
2012-01-23 18:51 ` Tejun Heo
2012-01-22 3:25 ` [PATCH 09/17] blkcg: move rcu_read_lock() outside of blkio_group get functions Tejun Heo
2012-01-22 3:25 ` [PATCH 10/17] blkcg: update blkg get functions take blkio_cgroup as parameter Tejun Heo
2012-01-22 3:25 ` [PATCH 11/17] blkcg: use q and plid instead of opaque void * for blkio_group association Tejun Heo
2012-01-22 3:25 ` [PATCH 12/17] blkcg: add blkio_policy[] array and allow one policy per policy ID Tejun Heo
2012-01-22 3:25 ` [PATCH 13/17] blkcg: use the usual get blkg path for root blkio_group Tejun Heo
2012-01-22 3:25 ` [PATCH 14/17] blkcg: factor out blkio_group creation Tejun Heo
2012-01-22 3:25 ` [PATCH 15/17] blkcg: don't allow or retain configuration of missing devices Tejun Heo
2012-01-22 3:25 ` [PATCH 16/17] blkcg: kill blkio_policy_node Tejun Heo
2012-01-22 3:25 ` [PATCH 17/17] blkcg: kill the mind-bending blkg->dev Tejun Heo
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