From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Przywara Subject: Re: Hypervisor crash(!) on xl cpupool-numa-split Date: Fri, 11 Feb 2011 08:39:10 +0100 Message-ID: <4D54E79E.3000800@amd.com> References: <4D41FD3A.5090506@amd.com> <201102021539.06664.stephan.diestelhorst@amd.com> <4D4974D1.1080503@ts.fujitsu.com> <201102021701.05665.stephan.diestelhorst@amd.com> <4D4A43B7.5040707@ts.fujitsu.com> <4D4A72D8.3020502@ts.fujitsu.com> <4D4C08B6.30600@amd.com> <4D4FE7E2.9070605@amd.com> <4D4FF452.6060508@ts.fujitsu.com> <4D50D80F.9000007@ts.fujitsu.com> <4D517051.10402@amd.com> <4D529BD9.5050200@amd.com> <4D52A2CD.9090507@ts.fujitsu.com> <4D5388DF.8040900@ts.fujitsu.com> <4D53AF27.7030909@amd.com> <4D53F3BC.4070807@amd.com> <4D54D478.9000402@ts.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D54D478.9000402@ts.fujitsu.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Juergen Gross Cc: George Dunlap , "xen-devel@lists.xensource.com" , "Diestelhorst, Stephan" List-Id: xen-devel@lists.xenproject.org Juergen Gross wrote: > On 02/10/11 15:18, Andre Przywara wrote: >> Andre Przywara wrote: >>> On 02/10/2011 07:42 AM, Juergen Gross wrote: >>>> On 02/09/11 15:21, Juergen Gross wrote: >>>>> Andre, George, >>>>> >>>>> >>>>> What seems to be interesting: I think the problem did always occur when >>>>> a new cpupool was created and the first cpu was moved to it. >>>>> >>>>> I think my previous assumption regarding the master_ticker was not >>>>> too bad. >>>>> I think somehow the master_ticker of the new cpupool is becoming active >>>>> before the scheduler is really initialized properly. This could >>>>> happen, if >>>>> enough time is spent between alloc_pdata for the cpu to be moved and >>>>> the >>>>> critical section in schedule_cpu_switch(). >>>>> >>>>> The solution should be to activate the timers only if the scheduler is >>>>> ready for them. >>>>> >>>>> George, do you think the master_ticker should be stopped in >>>>> suspend_ticker >>>>> as well? I still see potential problems for entering deep C-States. >>>>> I think >>>>> I'll prepare a patch which will keep the master_ticker active for the >>>>> C-State case and migrate it for the schedule_cpu_switch() case. >>>> Okay, here is a patch for this. It ran on my 4-core machine without any >>>> problems. >>>> Andre, could you give it a try? >>> Did, but unfortunately it crashed as always. Tried twice and made sure >>> I booted the right kernel. Sorry. >>> The idea with the race between the timer and the state changing >>> sounded very appealing, actually that was suspicious to me from the >>> beginning. >>> >>> I will add some code to dump the state of all cpupools to the BUG_ON >>> to see in which situation we are when the bug triggers. >> OK, here is a first try of this, the patch iterates over all CPU pools >> and outputs some data if the BUG_ON >> ((sdom->weight * sdom->active_vcpu_count) > weight_left) condition >> triggers: >> (XEN) CPU pool #0: 1 domains (SMP Credit Scheduler), mask: fffffffc003f >> (XEN) CPU pool #1: 0 domains (SMP Credit Scheduler), mask: fc0 >> (XEN) CPU pool #2: 0 domains (SMP Credit Scheduler), mask: 1000 >> (XEN) Xen BUG at sched_credit.c:1010 >> .... >> The masks look proper (6 cores per node), the bug triggers when the >> first CPU is about to be(?) inserted. > > Sure? I'm missing the cpu with mask 2000. > I'll try to reproduce the problem on a larger machine here (24 cores, 4 numa > nodes). > Andre, can you give me your xen boot parameters? Which xen changeset are you > running, and do you have any additional patches in use? The grub lines: kernel (hd1,0)/boot/xen-22858_debug_04.gz console=com1,vga com1=115200 module (hd1,0)/boot/vmlinuz-2.6.32.27_pvops console=tty0 console=ttyS0,115200 ro root=/dev/sdb1 xencons=hvc0 All of my experiments are use c/s 22858 as a base. If you use a AMD Magny-Cours box for your experiments (socket C32 or G34), you should add the following patch (removing the line) --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -803,7 +803,6 @@ static void pv_cpuid(struct cpu_user_regs *regs) __clear_bit(X86_FEATURE_SKINIT % 32, &c); __clear_bit(X86_FEATURE_WDT % 32, &c); __clear_bit(X86_FEATURE_LWP % 32, &c); - __clear_bit(X86_FEATURE_NODEID_MSR % 32, &c); __clear_bit(X86_FEATURE_TOPOEXT % 32, &c); break; case 5: /* MONITOR/MWAIT */ This is not necessary (in fact that reverts my patch c/s 22815), but raises the probability to trigger the bug, probably because it increases the pressure of the Dom0 scheduler. If you cannot trigger it with Dom0, try to create a guest with many VCPUs and squeeze it into a small CPU-pool. Good luck ;-) Andre. -- Andre Przywara AMD-OSRC (Dresden) Tel: x29712