Re: slow disk in NetBSD-7.0 under qemu

[Swift Griggs <swiftgriggs%gmail.com@localhost>]

On Thu, 24 Mar 2016, coypu%SDF.ORG@localhost wrote:
> Hi, I'm running NetBSD-7.0 in qemu with host being Debian Linux. Disk 
> operations are very slow (1MB/s unpacking local files, a bit better for 
> the disk ones).

It's totally un-accelerated. No kqemu or other kernel modules are available 
for NetBSD, AFAIK. It's just plain slow. There isn't much you can do about 
it since all the I/O is being done via CPU dynamic translation.

You could try to use a different IO subsystem driver, but I doubt it would 
help. While qemu is a nice stable tool, it's slower than frozen molasses 
on NetBSD. It's barely usable for most OS's even on a 4.0Ghz i7.

> I am invoking it with: qemu-system-x86_64 -m 512 -hda netbsd.img -cdrom 
> NetBSD-7.0-amd64.iso -curses

You already are doing -curses, which often helps a bit. The only other 
thing I can think of is that you might try with more memory. Perhaps a 
bigger cache for the buffer-cache will help. You could also try to run the 
image file in a RAM disk, though again, I doubt it'll help too much since 
the problem is just that qemu is 100% software emulation.

Since it doesn't look like folks have ever taken on getting something like 
FreeBSD's kernel module ported over (and I'm sure it'd be a lot of work), 
I'm just hoping hard that FreeBSD's Behyve or OpenBSD's new "Native 
Hypervisor" will be ready at some point and turn out to be portable. 
NetBSD's Xen support is pretty good, but it's still Xen, which I find to 
be unstable (even on Linux), invasive due to too much kernel futzing 
without modularity, and too painful to use on the desktop (no direct 
graphics options). The Python scripts they ship for management and service 
daemons like to blow up with a lot with tracebacks for me, but YMMV. I'm 
not trying to slam Xen. I'm sure some people have a decent time with it, 
just not me.

I'd prefer to use qemu over Xen, but I'm not skilled enough to port the 
kernel module so I acknowledge I have no right to that desire.

-Swift