Re: paravirtual drivers?

[Tomasz Chmielewski <mangoo-Nem3ZqsbT/g@public.gmane.org>]

Anthony Liguori schrieb:

(...)

> I don't believe a PV block driver is actually necessary.  Disk devices 
> are actually quite slow (unless you have a large array).  With a few 
> small changes (bump MMU cache up to 1024 and actually enable the aio 
> subsystem), SCSI emulation does as well as Xen's PV block driver (about 
> 210 mb/sec whereas native is around 250 mb/sec).  There's a lot of room 
> to optimize the SCSI emulation too since there are a number of copies in 
> that path.
> 
> The SCSI emulation is a lot like what one would design in a PV driver.  
> It supports multiple outstanding requests and doesn't require a whole 
> lot of exits to submit a request (it uses scripts).

How does one enable SCSI emulation?

"qemu-system-x86_64 -h" gives no hints about SCSI (at least in KVM-18); 
similarly, I didn't find anything in the archive or in the wiki.


Certainly, there is a kvm-18/qemu/hw/scsi-disk.c file, so it's like the 
feature is there...

Is it possible to boot a guest from a "SCSI-emulated" device?


-- 
Tomasz Chmielewski
http://wpkg.org

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