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Date: Tue, 27 Feb 2007 09:54:13 +0100 From: Mike Galbraith <efault@....de> To: Ingo Molnar <mingo@...e.hu> Cc: Michal Piotrowski <michal.k.k.piotrowski@...il.com>, Thomas Gleixner <tglx@...utronix.de>, Adrian Bunk <bunk@...sta.de>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "David P. Reed" <dpreed@...d.com>, Ayaz Abdulla <aabdulla@...dia.com>, jgarzik@...ox.com, netdev@...r.kernel.org, Albert Hopkins <kernel@...duk.letterboxes.org>, Bob Tracy <rct@...rkin.frus.com>, Mark Brown <broonie@...ena.org.uk>, "Michael S. Tsirkin" <mst@...lanox.co.il> Subject: Re: 2.6.21-rc1: known regressions (v2) (part 2) On Tue, 2007-02-27 at 09:33 +0100, Ingo Molnar wrote: > * Michal Piotrowski <michal.k.k.piotrowski@...il.com> wrote: > > > Thomas Gleixner napisaĆ(a): > > > Adrian, > > > > > > On Mon, 2007-02-26 at 23:05 +0100, Adrian Bunk wrote: > > >> Subject : kernel BUG at kernel/time/tick-sched.c:168 (CONFIG_NO_HZ) > > >> References : http://lkml.org/lkml/2007/2/16/346 > > >> Submitter : Michal Piotrowski <michal.k.k.piotrowski@...il.com> > > >> Handled-By : Thomas Gleixner <tglx@...utronix.de> > > >> Status : problem is being debugged > > > > > > The BUG_ON() was replaced by a warning printk(). The BUG_ON() exposed a > > > problem with the SMT scheduler. See below. > > > > > >> Subject : BUG: soft lockup detected on CPU#0 > > >> NOHZ: local_softirq_pending 20 (SMT scheduler) > > >> References : http://lkml.org/lkml/2007/2/20/257 > > >> Submitter : Michal Piotrowski <michal.k.k.piotrowski@...il.com> > > >> Handled-By : Thomas Gleixner <tglx@...utronix.de> > > >> Ingo Molnar <mingo@...e.hu> > > >> Status : problem is being debugged > > > > > > Patch available, not confirmed yet. > > > > > > > I can confirm that the bug is fixed (over 20 hours of testing should > > be enough). > > thanks alot! I think this thing was a long-term performance/latency > regression in HT scheduling as well. Agreed. I was recently looking at that spot because I found that niced tasks were taking latency hits, and disabled it, which helped a bunch. I also can't understand why it would be OK to interleave a normal task with an RT task sometimes, but not others.. that's meaningless to the RT task. IMHO, SMT scheduling should be a buyer beware thing. Maximizing your core utilization comes at a price, but so does disabling it, so I think letting the user decide what he wants is the right thing to do. -Mike - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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