linux-kernel - Re: [RFC/PATCH] Add sysfs control to modify a user's cpu share

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Message-ID: <20071001144402.GA3505@elte.hu>
Date:	Mon, 1 Oct 2007 16:44:02 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>
Cc:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Mike Galbraith <efault@....de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	lkml <linux-kernel@...r.kernel.org>, maneesh@...ux.vnet.ibm.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sudhir Kumar <skumar@...ux.vnet.ibm.com>
Subject: Re: [RFC/PATCH] Add sysfs control to modify a user's cpu share


hi Dhaval,

* Dhaval Giani <dhaval@...ux.vnet.ibm.com> wrote:

> Hi Ingo,
> 
> Adds tunables in sysfs to modify a user's cpu share.
> 
> A directory is created in sysfs for each new user in the system.
> 
> 	/sys/kernel/uids/<uid>/cpu_share
> 
> Reading this file returns the cpu shares granted for the user.
> Writing into this file modifies the cpu share for the user. Only an 
> administrator is allowed to modify a user's cpu share.
> 
> Ex: 
> 	# cd /sys/kernel/uids/
> 	# cat 512/cpu_share
> 	1024
> 	# echo 2048 > 512/cpu_share
> 	# cat 512/cpu_share
> 	2048
> 	#

looks good to me! I think this API is pretty straightforward. I've put 
this into my tree and have updated the sched-devel git tree:

 git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-devel.git

but there seems to be a bug in it, i get this:

 kobject_add failed for 500 with -EEXIST, don't try to register things with the same name in the same directory.
  [<c01e1730>] kobject_shadow_add+0x13b/0x169
  [<c01e1795>] kobject_set_name+0x28/0x91
  [<c01299d5>] user_kobject_create+0x6a/0x90
  [<c0129d3c>] alloc_uid+0x141/0x181
  [<c012d05c>] set_user+0x1c/0x91
  [<c012e4c7>] sys_setresuid+0xd9/0x17d
  [<c0103cf6>] sysenter_past_esp+0x5f/0x85
  =======================

	Ingo
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