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Re: [Qemu-devel] Performance regression "ioport: Switch dispatching to m
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] Performance regression "ioport: Switch dispatching to memory core layer" |
Date: |
Mon, 15 Jul 2013 22:31:53 +0800 |
On Mon, Jul 15, 2013 at 7:01 PM, Jan Kiszka <address@hidden> wrote:
> On 2013-07-15 12:52, Stefan Hajnoczi wrote:
>> The following qemu.git commit adds a ~2 minute regression in boot time
>> to a x86_64 live CD:
>>
>> commit b40acf99bef69fa8ab0f9092ff162fde945eec12
>> Author: Jan Kiszka <address@hidden>
>> Date: Mon Jun 24 10:45:09 2013 +0200
>>
>> ioport: Switch dispatching to memory core layer
>>
>> After the ISOLINUX menu, the display goes white and sits there for about
>> 2 minutes on my laptop before the usual Linux boot screen appears.
>>
>> $ qemu-system-x86_64 -enable-kvm -cpu host -m 1024 -cdrom ~/iso/livecd.iso
>>
>> The parent commit immediately goes to the usual boot screen after
>> ISOLINUX. Unfortunately I don't have a ISO download link for the live
>> CD.
>
> Can you share it otherwise (before I spend time on recreating something
> that does not trigger it)?
I reproduced this now with an installed RHEL 6.4 guest (no ISO).
>>
>> Any ideas?
>
> What does perf say during that time? What ftrace regarding the port
> numbers and access types?
The guest kernel prints the following IPMI initialization output:
acpiphp: Slot [31] registered
ipmi message handler version 39.2
IPMI System Interface driver.
ipmi_si: Adding default-specified kcs state machine
ipmi_si: Trying default-specified kcs state machine at i/o address
0xca2, slave address 0x0, irq 0
ipmi_si: There appears to be no BMC at this location
ipmi_si: Adding default-specified smic state machine
ipmi_si: Trying default-specified smic state machine at i/o address
0xca9, slave address 0x0, irq 0
ipmi_smic_drv: smic hosed: state = SMIC_OP_OK, status != SMIC_SC_SMS_READY
ipmi_si: There appears to be no BMC at this location
ipmi_si: Adding default-specified bt state machine
ipmi_si: Trying default-specified bt state machine at i/o address
0xe4, slave address 0x0, irq 0
Refined TSC clocksource calibration: 2895.094 MHz.
[...wait...]
IPMI BT: timeout in RD_WAIT [ ] 1 retries left
Before this commit the guest boots immediately and does not get stuck
in IPMI initialization.
kvmstat:
kvm_exit 2567180 3007
kvm_entry 2567180 3007
kvm_inj_virq 16226 1002
kvm_emulate_insn 2044389 1001
kvm_userspace_exit 538441 1001
kvm_pio 502055 1001
kvm_msr 16182 1001
kvm_apic 15994 1001
kvm_eoi 15876 1001
kvm_apic_accept_irq 15876 1001
kvm_pv_eoi 15763 1001
kvm_mmio 2006613 0
vcpu_match_mmio 1970359 0
kvm_cr 144706 0
kvm_cpuid 33451 0
kvm_set_irq 1032 0
kvm_pic_set_irq 1024 0
kvm_ioapic_set_irq 1024 0
kvm_page_fault 1020 0
kvm_ack_irq 277 0
kvm_inj_exception 33 0
kvm_fpu 6 0
kvm_track_tsc 2 0
kvm_apic_ipi 2 0
kvm_update_master_clock 2 0
IPMI seems like the smoking gun. perf shows a number of mmio/pio/msr
accesses, the longest repeated sequence is:
qemu-system-x86 7318 [003] 4188.001381: kvm:kvm_pio: pio_read at
0xe4 size 1 count 1
qemu-system-x86 7318 [003] 4188.002343: kvm:kvm_msr: msr_write 838 = 0xd6ff
Stefan