Re: [Qemu-discuss] virtio-scsi really slow init with ArchLinux kernel

[Chris]

On Wed, Jul 11, 2018 at 12:43 PM, Greg Kurz <address@hidden> wrote:
> I've been observing a similar delay on ppc64 with fedora28 guests:
>
> # dmesg | egrep 'scsi| sd '
> [    1.530946] scsi host0: Virtio SCSI HBA
> [    1.532452] scsi 0:0:0:0: Direct-Access     QEMU     QEMU HARDDISK    2.5+ 
> PQ: 0 ANSI: 5
> [   21.928378] sd 0:0:0:0: Power-on or device reset occurred
> [   21.930012] sd 0:0:0:0: Attached scsi generic sg0 type 0
> [   21.931554] sd 0:0:0:0: [sda] 83886080 512-byte logical blocks: (42.9 
> GB/40.0 GiB)
> [   21.931929] sd 0:0:0:0: [sda] Write Protect is off
> [   21.933110] sd 0:0:0:0: [sda] Mode Sense: 63 00 00 08
> [   21.934084] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, 
> doesn't support DPO or FUA
> [   21.943566] sd 0:0:0:0: [sda] Attached SCSI disk
>
> Kernel version is 4.16.16-300.fc28.ppc64. And I cannot reproduce the
> issue with other distros that have an older kernel, eg, ubuntu 18.04
> with kernel 4.15.0-23-generic.
>
> My first guess is that it might be a kernel-side regression introduced
> in 4.16... maybe bisect ?

Interesting. I just tried kernel 4.17.5 from the mainline ppa on
Ubuntu 18.04 and now there is a delay. It's only 7.5 seconds but still
noticeable. There was previously no delay with the 4.15 kernel.

Definitely seems like it could be something introduced in kernel 4.16.

Chris