linux-kernel - Re: load balancing regression since commit 367456c7

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: <1334681054.3796.28.camel@schen9-DESK>
Date:	Tue, 17 Apr 2012 09:44:14 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Alex Shi <alex.shi@...el.com>, Ying <ying.huang@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: load balancing regression since commit 367456c7

On Tue, 2012-04-17 at 14:09 +0200, Peter Zijlstra wrote:
> On Tue, 2012-04-10 at 18:06 -0700, Tim Chen wrote:
> >                   |--56.52%-- load_balance
> >                   |          idle_balance
> >                   |          __schedule
> >                   |          schedule 
> 
> Ahh, I know why I didn't see it, I have a CONFIG_PREEMPT kernel and
> idle_balancing stops once its gotten a single task over instead of
> achieving proper balance.
> 
> And since hackbench generates insanely long runqueues and the patch that
> caused your regression 'fixed' the lock-breaking it will now iterate the
> entire runqueue if needed to achieve balance, which hurts.
> 
> I think the patch I send ought to work, let me try disabling
> CONFIG_PREEMPT.
> --

yes, CONFIG_PREEMPT is turned off on my side.  With the patch that you
sent, the slowed down went from a factor of 4 down to a factor 2. 

So the run time is now twice as long vs four time as long vs v3.3
kernel.

Tim

--
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/