Re: DMA doesn't work since "make ata port as parent device of scsi host"

["Jörg Sommer" <joerg@alea.gnuu.de>]

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Lin Ming hat am Thu 15. Mar, 11:26 (+0800) geschrieben:
> On Thu, 2012-03-15 at 09:59 +0800, Lin Ming wrote:
> > On Thu, 2012-03-15 at 02:48 +0100, Jörg Sommer wrote:
> > > Hi,
> > > 
> > > I'm getting these messages in a KVM virtualized host and the access to
> > > the disks is very slow. Using libata.dma=0 suppresses the warnings, but
> > > the disks are still slow.
> > 
> > Hi Jörg,
> > 
> > Let me try to reproduce this issue first.
> 
> I tried below commands on x86_32, but can't reproduce it.
> 
> qemu-system-i386 -kernel /root/vmlinuz-3.3.0-rc7 -append "root=/dev/sda1
> zcache" -hda /root/debian-32.img -hdb /root/data.img
> 
> Maybe because i386 uses different ata controller than ppc(ata_piix vs
> pata-macio).
> 
> I'll try qemu-system-ppc.
> 
> Did you need to run some workload to trigger these warings?
> Or did you get these warnings right after booting the VM?

These warnings come up before »INIT started«. I don't have to do
anything, just wait and see.

# truncate -s100M /mnt/data/new
# mke2fs -Fq /mnt/data/new
# mount -o loop /mnt/data/new /mnt/other
# cp --parents /bin/zsh-static /mnt/other/zsh
# umount /mnt/other
# qemu-system-ppc -enable-kvm -M mac99 -cpu G4 -k de -kernel /boot/vmlinuz-3.3.0-rc5-04520-g8d233c0 -append 'root=/dev/sda ro console=ttyPZ0 init=/zsh' -hda /mnt/data/new

I've uploaded my config and the kernel:
http://alioth.debian.org/~jo-guest/config-3.3.0-rc5-04520-g8d233c0
http://alioth.debian.org/~jo-guest/vmlinuz-3.3.0-rc5-04520-g8d233c0

You have to switch to the serial console (Ctrl-Alt-3 or with -nographic
Ctrl-a c). All kernel messages arrive there.

> Would you please try to disable ata port runtime pm?
> You can disable it by, for example,

Is this also possible with a kernel parameter? It takes very long until I
get a shell prompt.

Bye, Jörg.
-- 
But in the case of "git revert", it should be an ancestor (or the user
is just insane, in which case it doesn't matter - insane people can do
insane things)
Linus Torvalds <alpine.LFD.1.00.0801041031590.2811@woody.linux-foundation.org>

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