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Date: Mon, 30 Nov 2015 23:55:09 +0100 From: Sander Eikelenboom <linux@...elenboom.it> To: Boris Ostrovsky <boris.ostrovsky@...cle.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, david.vrabel@...rix.com, linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org Subject: Re: [Xen-devel] linux 4.4 Regression: 100% cpu usage on idle pv guest under Xen with single vcpu. On 2015-11-30 23:54, Boris Ostrovsky wrote: > On 11/30/2015 04:46 PM, Sander Eikelenboom wrote: >> On 2015-11-30 22:45, Konrad Rzeszutek Wilk wrote: >>> On Sat, Nov 28, 2015 at 04:47:43PM +0100, Sander Eikelenboom wrote: >>>> Hi all, >>>> >>>> I have just tested a 4.4-rc2 kernel (current linus tree) + the tip >>>> tree >>>> pulled on top. >>>> >>>> Running this kernel under Xen on PV-guests with multiple vcpus goes >>>> well (on >>>> idle < 10% cpu usage), >>>> but a guest with only a single vcpu doesn't idle at all, it seems a >>>> kworker >>>> thread is stuck: >>>> root 569 98.0 0.0 0 0 ? R 16:02 12:47 >>>> [kworker/0:1] >>>> >>>> Running a 4.3 kernel works fine with a single vpcu, bisecting would >>>> probably >>>> quite painful since there were some breakages this merge window with >>>> respect >>>> to Xen pv-guests. >>>> >>>> There are some differences in the diff's from booting a 4.3, >>>> 4.4-single, >>>> 4.4-multi cpu boot: >>> >>> Boris has been tracking a bunch of them. I am attaching the latest >>> set of >>> patches I've to carry on top of v4.4-rc3. >> >> Hi Konrad, >> >> i will test those, see if it fixes all my issues and report back > > They shouldn't help you ;-( (and I just saw a message from you > confirming this) > > The first one fixes a 32-bit bug (on bare metal too). The second fixes > a fatal bug for 32-bit PV guests. The other two are code > improvements/cleanup. One of these patches also fixes a bug i was having with a pci-passthrough device in a HVM that wasn't working (depending on which dom0-kernel i was using (4.3 or 4.4)), but didn't report yet. Fingers crossed but i think this pv-guest single vcpu issue is the last i'm troubled by for now ;) -- Sander > >> >> Thanks :) >> >> -- Sander >> >>>> Between 4.3 and 4.4-single: >>>> >>>> -NR_IRQS:4352 nr_irqs:32 16 >>>> +Using NULL legacy PIC >>>> +NR_IRQS:4352 nr_irqs:32 0 > > This is fine, as long as you have > b4ff8389ed14b849354b59ce9b360bdefcdbf99c. > >>>> >>>> -cpu 0 spinlock event irq 17 >>>> +cpu 0 spinlock event irq 1 > > This is strange. I wouldn't expect spinlocks to use legacy irqs. > >>>> >>>> and later on: >>>> >>>> -hctosys: unable to open rtc device (rtc0) >>>> +rtc_cmos rtc_cmos: hctosys: unable to read the hardware clock >>>> >>>> +genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 >>>> (rtc0) >>>> +hvc_open: request_irq failed with rc -16. >>>> +Warning: unable to open an initial console. >>>> >>>> >>>> between 4.4-single and 4.4-multi: >>>> >>>> Using NULL legacy PIC >>>> -NR_IRQS:4352 nr_irqs:32 0 >>>> +NR_IRQS:4352 nr_irqs:48 0 > > This is probably OK too since nr_irqs depend on number of CPUs. > > I think something is messed up with IRQ. I saw last week something > from setup_irq() generating a stack dump (warninig) for rtc_cmos but > it appeared harmless at that time and now I don't see it anymore. > > -boris > > >>>> >>>> and later on: >>>> >>>> -rtc_cmos rtc_cmos: hctosys: unable to read the hardware clock >>>> +hctosys: unable to open rtc device (rtc0) >>>> >>>> -genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 >>>> (rtc0) >>>> -hvc_open: request_irq failed with rc -16. >>>> -Warning: unable to open an initial console. >>>> >>>> attached: >>>> - dmesg with 4.3 kernel with 1 vcpu >>>> - dmesg with 4.4 kernel with 1 vpcu >>>> - dmesg with 4.4 kernel with 2 vpcus >>>> - .config of the 4.4 kernel is attached. >>>> >>>> -- Sander >>>> >>>> -- 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/
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