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] [day] [month] [year] [list]
Message-ID: <alpine.DEB.1.10.0810110952190.12625@gandalf.stny.rr.com>
Date:	Sat, 11 Oct 2008 09:55:37 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <clark.williams@...il.com>
Subject: Re: [PATCH] sched: fair scheduler should not resched rt tasks


On Sat, 11 Oct 2008, Peter Zijlstra wrote:

> On Sat, 2008-10-11 at 03:01 -0400, Steven Rostedt wrote:
> > Using ftrace, I noticed latencies in real-time tasks where they were
> > needlessly calling schedule due to sched_fair sending out time slices.
> > 
> > This patch prevents a call to resched_task by the sched fair class if
> > the task it wants to reschedule is an rt task.
> 
> Right, thats not a good thing, however this patch looks wrong, we should
> never call hrtick_start_fair() on a rt task to begin with.

Great! I don't care which way we fix this. This was making noticeable
latencies against rt tasks.

> 
> The way I can see that happening is through enqueue/dequeue_task_fair()
> where we want to re-programm the hrtick because nr_running changes (and
> thus the current tasks desired runtime).

My original patch was more like this one, but I wasn't sure if I was 
skipping any calculations that were assumed to be made. Thus, I wrote the 
bare minimum and sent it out CC'ing the experts. Looks like my plan worked 
;-)

-- Steve


> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

Acked-by: Steven Rostedt <srostedt@...hat.com>

--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ