While there is no delay with stable 4.7.15 kernel, there is a delay less than 8 seconds with ubuntu ppa kernel 4.7.15 on amd64. Perhaps this is related to kernel config file, as I used "make defconfig" with scsi virtio enabled manually.
[ 0.905328] scsi host2: Virtio SCSI HBA [ 0.905810] scsi 2:0:0:0: Direct-Access QEMU QEMU HARDDISK 2.5+ PQ: 0 ANSI: 5 [ 0.912323] FDC 0 is a S82078B [ 0.927547] PCI Interrupt Link [LNKC] enabled at IRQ 10 [ 1.250295] e1000 0000:00:03.0 eth0: (PCI:33MHz:32-bit) 52:54:00:12:34:56 [ 1.250452] e1000 0000:00:03.0 eth0: Intel(R) PRO/1000 Network Connection [ 1.251320] e1000 0000:00:03.0 ens3: renamed from eth0 [ 1.600095] tsc: Refined TSC clocksource calibration: 3392.142 MHz [ 1.600250] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x30e54fbd081, max_idle_ns: 440795321209 ns [ 7.696221] random: fast init done [ 9.264477] sd 2:0:0:0: Power-on or device reset occurred [ 9.264743] sd 2:0:0:0: Attached scsi generic sg1 type 0 [ 9.265183] sd 2:0:0:0: [sda] 62914560 512-byte logical blocks: (32.2 GB/30.0 GiB) [ 9.265460] sd 2:0:0:0: [sda] Write Protect is off [ 9.265576] sd 2:0:0:0: [sda] Mode Sense: 63 00 00 08 [ 9.265656] sd 2:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [ 9.266258] sda: sda1 [ 9.266638] sd 2:0:0:0: [sda] Attached SCSI disk Dongli Zhang On 07/12/2018 01:35 PM, Dongli Zhang wrote: > Hi Chris, > > On 07/12/2018 01:45 AM, Chris wrote: >> On Wed, Jul 11, 2018 at 12:43 PM, Greg Kurz <gr...@kaod.org> 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. > > I did not observe any delay with stable 4.17.5 on ubuntu 18.04 (I built the > kernel myself with CONFIG_SCSI_VIRTIO=y): > > # qemu-system-x86_64 -drive > file=/home/zhang/img/ubuntu1804.qcow2,format=qcow2,if=none,id=virt1 -device > virtio-scsi-pci,id=virt1 -device scsi-hd,drive=virt1 -m 4096M -enable-kvm > -smp 6 > -net nic -net user,hostfwd=tcp::5022-:22 -kernel > /home/zhang/test/linux-4.17.5/arch/x86_64/boot/bzImage -append "root=/dev/sda1 > init=/sbin/init text" -enable-kvm > > > # uname -r > 4.17.5 > > [0.190434] scsi host0: Virtio SCSI HBA > [0.190924] scsi 0:0:0:0: Direct-Access QEMU QEMU HARDDISK 2.5+ PQ: > 0 > ANSI: 5 > [0.206282] random: fast init done > [0.216651] sd 0:0:0:0: Power-on or device reset occurred > [0.216907] sd 0:0:0:0: Attached scsi generic sg0 type 0 > [0.217207] ata_piix 0000:00:01.1: version 2.13 > [0.217613] sd 0:0:0:0: [sda] 62914560 512-byte logical blocks: (32.2 GB/30.0 > GiB) > [0.217959] sd 0:0:0:0: [sda] Write Protect is off > [0.218152] sd 0:0:0:0: [sda] Mode Sense: 63 00 00 08 > [0.218193] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, > doesn't > support DPO or FUA > > > In addition, I could not reproduce with '4.18-rc4' or 'v4.17-rc7'. > > > Dongli Zhang > >> >> Definitely seems like it could be something introduced in kernel 4.16. >> >> Chris >> >
