Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030567AbWBNK4Q (ORCPT ); Tue, 14 Feb 2006 05:56:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030568AbWBNK4Q (ORCPT ); Tue, 14 Feb 2006 05:56:16 -0500 Received: from mtagate3.de.ibm.com ([195.212.29.152]:4135 "EHLO mtagate3.de.ibm.com") by vger.kernel.org with ESMTP id S1030567AbWBNK4P (ORCPT ); Tue, 14 Feb 2006 05:56:15 -0500 Date: Tue, 14 Feb 2006 11:56:08 +0100 From: Heiko Carstens To: Olaf Hering Cc: Ingo Molnar , Hannes Reinecke , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: calibrate_migration_costs takes ages on s390 Message-ID: <20060214105608.GD19896@osiris.boeblingen.de.ibm.com> References: <20060213102634.GA4677@osiris.boeblingen.de.ibm.com> <20060213104645.GA17173@elte.hu> <20060213234254.GA5368@suse.de> <20060214000807.GA6188@suse.de> <20060214080942.GC19896@osiris.boeblingen.de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060214080942.GC19896@osiris.boeblingen.de.ibm.com> User-Agent: mutt-ng/devel-r781 (Linux) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2366 Lines: 58 > I did a quick git bisect search. This is one is the hurting one: > > Author: Ingo Molnar 2006-02-07 21:58:54 > Committer: Linus Torvalds 2006-02-08 01:12:33 > Parent: 8519fb30e438f8088b71a94a7d5a660a814d3872 ([PATCH] mm: compound release fix) > Child: 0d4c3e7a8c65892c7d6a748fdbb4499e988880db ([PATCH] unshare system call -v5: Documentation file) > > The fix is to include a __delay(1) call in the loop, to correctly approximate > the intended delay timeout of 1 second. The code assumes that every > architecture implements __delay(1) to last around 1/(loops_per_jiffy*HZ) > seconds. > > I guess we're once again suffering from being a virtualized platform: the > formerly used call to cpu_relax() informed the underlying hypervisor that > we want to give up the current cpu while __delay() keeps it. > Unless we're scheduled away involuntarily. > The "Detect Soft Lockups" option doesn't make too much sense too on our > platform, since we get a lot of false positives. > Quick fix: turn off the options CONFIG_DEBUG_SPINLOCK and > CONFIG_DETECT_SOFTLOCKUP. Wrong analysis. Our __delay() implementation is broken. This doesn't help for the CONFIG_DETECT_SOFTLOCKUP case, but at least CONFIG_DEBUG_SPINLOCK works again with this. Andrew, could you pick this one up, or should I send it separately? [PATCH] s390: fix __delay implementation From: Heiko Carstens Fix __delay implementation. Called with an argument "1" or "0" it would loop nearly forever (since (1/2)-1 = 0xffffffff). Signed-off-by: Heiko Carstens --- arch/s390/lib/delay.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c index e96c35b..71f0a2f 100644 --- a/arch/s390/lib/delay.c +++ b/arch/s390/lib/delay.c @@ -30,7 +30,7 @@ void __delay(unsigned long loops) */ __asm__ __volatile__( "0: brct %0,0b" - : /* no outputs */ : "r" (loops/2) ); + : /* no outputs */ : "r" ((loops/2) + 1)); } /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/