linux-kernel - Re: [PATCH] sched: fix off-by-one bug in balance

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: <1239795719.22720.2231.camel@laptop>
Date:	Wed, 15 Apr 2009 13:41:59 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	miaox@...fujitsu.com
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: fix off-by-one bug in balance_tasks()

On Wed, 2009-04-15 at 10:49 +0800, Miao Xie wrote:
> If the load that need be moved equals the half weight of a task, I think
> it is unnecessary to move this task. Or this task will be moved back and
> forth.

That's actually desirable. Consider the 3 tasks on 2 cpus statically
infeasible scenario. There you'd want the tasks to bounce around a bit
in order to provide fairness.

> Signed-off-by: Miao Xie <miaox@...fujitsu.com>
> ---
>  kernel/sched.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 5724508..44926c8 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -3085,7 +3085,7 @@ next:
>  	if (!p || loops++ > sysctl_sched_nr_migrate)
>  		goto out;
>  
> -	if ((p->se.load.weight >> 1) > rem_load_move ||
> +	if ((p->se.load.weight >> 1) >= rem_load_move ||
>  	    !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) {
>  		p = iterator->next(iterator->arg);
>  		goto next;

--
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/