linux-kernel - Re: [PATCH/RFC] do not count frozen tasks toward load

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: <1239240103.9869.1.camel@nigel-laptop>
Date:	Thu, 09 Apr 2009 11:21:43 +1000
From:	Nigel Cunningham <ncunningham-lkml@...a.org.au>
To:	Nathan Lynch <ntl@...ox.com>
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org,
	linux-pm@...ts.linux-foundation.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Helsley <matthltc@...ibm.com>
Subject: Re: [PATCH/RFC] do not count frozen tasks toward load

Hi again.

On Wed, 2009-04-08 at 19:45 -0500, Nathan Lynch wrote:
> Freezing tasks via the cgroup freezer causes the load average to climb
> because the freezer's current implementation puts frozen tasks in
> uninterruptible sleep (D state).
> 
> Some applications which perform job-scheduling functions consult the
> load average when making decisions.  If a cgroup is frozen, the load
> average does not provide a useful measure of the system's utilization
> to such applications.  This is especially inconvenient if the job
> scheduler employs the cgroup freezer as a mechanism for preempting low
> priority jobs.  Contrast this with using SIGSTOP for the same purpose:
> the stopped tasks do not count toward system load.
> 
> Change task_contributes_to_load() to return false if the task is
> frozen.  This results in /proc/loadavg behavior that better meets
> users' expectations.
> 
> Signed-off-by: Nathan Lynch <ntl@...ox.com>
> ---
>  include/linux/sched.h |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 011db2f..f8af167 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -202,7 +202,8 @@ extern unsigned long long time_sync_thresh;
>  #define task_is_stopped_or_traced(task)	\
>  			((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)
>  #define task_contributes_to_load(task)	\
> -				((task->state & TASK_UNINTERRUPTIBLE) != 0)
> +				((task->state & TASK_UNINTERRUPTIBLE) != 0 && \
> +				 (task->flags & PF_FROZEN) == 0)
>  
>  #define __set_task_state(tsk, state_value)		\
>  	do { (tsk)->state = (state_value); } while (0)

Tested-by: Nigel Cunningham <nigel@...onice.net>

Looks good to me (though I like Andrew's point about using task_frozen).

nigel@...el-laptop:~$ cat /proc/loadavg 
0.34 0.27 0.12 1/251 9001
nigel@...el-laptop:~$ sudo hibernate
nigel@...el-laptop:~$ cat /proc/loadavg 
0.52 0.33 0.14 2/250 9807
nigel@...el-laptop:~$ 


--
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/