Poor virtio performance on Scaleway ARM systems

[Peter Jeremy]

On 2018-Oct-23 10:04:04 -0700, John Baldwin <jhb at FreeBSD.org> wrote:
>On 10/23/18 8:46 AM, Greg V wrote:
>> On Sun, Sep 16, 2018 at 9:46 PM, Peter Jeremy <peter at rulingia.com> 
>> wrote:
>>> I have been playing with the 4-core ARM64 VPSs on 
>>> https://www.scaleway.com
>>> and notice that the disk I/O performance (using virtio_blk) is 
>>> abyssmal.
>>>
>>> The only oddity I've found is that FreeBSD is reporting very high 
>>> interrupt
>>> rates on gic0,p11, gic0,s4 and gic0,s5 whilst disk I/O is occurring.
>>> Unfortunately, I can't tell what is attached to those interrupts (it's
>>> not obvious from the dmesg and reported as "+").
>> gic0,s4 correlates to network activity.
>> gic0,s5 correlates to disk activity.
>> 
>> echo 'hw.pci.honor_msi_blacklist="0"' >> /boot/loader.conf

>Can you make 'pciconf -lc' output available?  There is a "generic"
>blacklist that assumes we will see a host bridge device with PCI-e
>or PCI-X and if neither of those is present we also blacklist MSI.
>However, we can certainly figure out how to make this work out of
>the box.

$ sudo pciconf -lc
hostb0 at pci0:0:0:0:      class=0x060000 card=0x11001af4 chip=0x00081b36 rev=0x00 hdr=0x00
virtio_pci0 at pci0:0:1:0: class=0x020000 card=0x00011af4 chip=0x10001af4 rev=0x00 hdr=0x00
    cap 11[98] = MSI-X supports 3 messages
                 Table in map 0x14[0x0], PBA in map 0x14[0x800]
    cap 09[84] = vendor (length 20)
    cap 09[70] = vendor (length 20)
    cap 09[60] = vendor (length 16)
    cap 09[50] = vendor (length 16)
    cap 09[40] = vendor (length 16)
virtio_pci1 at pci0:0:2:0: class=0x010000 card=0x00021af4 chip=0x10011af4 rev=0x00 hdr=0x00
    cap 11[98] = MSI-X supports 2 messages
                 Table in map 0x14[0x0], PBA in map 0x14[0x800]
    cap 09[84] = vendor (length 20)
    cap 09[70] = vendor (length 20)
    cap 09[60] = vendor (length 16)
    cap 09[50] = vendor (length 16)
    cap 09[40] = vendor (length 16)

-- 
Peter Jeremy
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