RE: [Qemu-devel] does ext4 cause problems? (not data loss)

[Laurent Vivier]

Hi,

>I have the latest version of Ubuntu, Jaunty, and I have converted my fs to
>ext4.  Attempting to run a qcow image of WinXP Pro, backed by a qcow
>image, on 0.10.3, even with kernel-kqemu is near impossible.  Commands:
>
>#!/bin/sh
>
>export QEMU_AUDIO_DRV=sdl
>export SDL_VIDEODRVER=dga
>sudo chmod 666 /dev/kqemu
>/opt/qemu-0.10.3/bin/qemu -L /opt/qemu-0.10.3/share/qemu/ -kernel-kqemu
>-hda winxp-200905.qcow -m 512 -usbdevice tablet -localtime -net
>nic,model=rtl8139 -net user -soundhw sb16 -redir tcp:103389::3389
>
>My host computer spends most of its time doing disk writes and my guest is
>impossible to use.  The computer begins to boot, requests re-activation
>(which I deny until I can get this straightened out) and then runs
>slooooowly.  It does run, but I don't know why it is so slow.  One of the
>reasons I upgraded to ext4 was to enjoy better Qemu performance.
>
>I have instead created a sparse file and formatted it with reiserfs (which
>on my crappy laptop gives very good qemu performance) and mounted it as a
>loop filesystem.  Performance returns as expected and massive disk writing
>ceases.
>
>Anyone know what's up here?  Please CC me as I'm not on the list.  Thanks.

Perhaps a link with that :

http://lwn.net/Articles/327107/

try to change your journaling mode to use "data=ordered".
(see man mount(8) or tune2fs(8))

Regards,
Laurent



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