linux-kernel - Re: [BUG] sched: fair group's bug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4966BA32.5000400@cn.fujitsu.com>
Date:	Fri, 09 Jan 2009 10:45:06 +0800
From:	Miao Xie <miaox@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] sched: fair group's bug

on 2009-1-8 9:30 Miao Xie wrote:
> I tested fair group scheduler on my hyper-threading x86_64 box(2 CPU * 2 HT)
> and found the deviation of the groups' CPU usage was larger than 2.6.26
> when *offline* a CPU or do hotplug frequently. It is less than 1% On 2.6.26，but
> On current kernel, it is often greater than 4%, even than 10% by accident.
> 

This patch fixed the following problems. But the regression above still exists.

commit 0a582440ff546e2c6610d1acec325e91b4efd313
Author: Mike Galbraith <efault@....de>
Date:   Fri Jan 2 12:16:42 2009 +0100

    sched: fix sched_slice()

    Impact: fix bad-interactivity buglet

    Fix sched_slice() to emit a sane result whether a task is currently
    enqueued or not.

    Signed-off-by: Mike Galbraith <efault@....de>
    Tested-by: Jayson King <dev@...sonking.com>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>

> 
> Besides that, We found other problems by the attached program.
> 1. some tasks are hungry in the fair group.
> 	Steps to reproduce:
> 	# mkdir /dev/cpuctl
> 	# mount -t cgroup -o cpu,noprefix xxx /dev/cpuctl
> 	# ./cpuctl -g 1 -v
> 	--------------------
> 	1th Check Result:
> 	Group	Shares	Actual(%)	Expect(%)
> 	0	1024	100.00		100.00
> 	Each task's usage:
> 		Task in Group 0:
> 			Task	Usage(%)
> 			5395	0.000000
> 			5396	0.000000
> 		 	5397	0.000000
> 			5398	16.677785
> 			5399	16.677785
> 			5400	16.744496
> 			5401	16.611074
> 			5402	33.288859
> 
> 2. some groups broke the limit of the fair group and get more CPU time When
>    the groups is hiberarchy. Such as:
> 		top group
> 		    |
> 		 group 1
> 		/	\
> 	      task1	group 2
> 			   |
> 			task 2
> 	Steps to reproduce:
> 	# mkdir /dev/cpuctl
> 	# mount -t cgroup -o cpu,noprefix xxx /dev/cpuctl
> 	# ./cpuctl -H
> 	-------------------------
> 	Group	Shares	Actual(%)	Expect(%)
> 	0	1024	60.17		88.89
> 	1	1024    39.83		11.11
> 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/