Re: [Qemu-devel] [v8 Patch 0/6]Qemu: Host pagecache setting from cmdline and monitor

[Supriya Kannery]

On 11/07/2011 02:19 PM, Zhi Yong Wu wrote:
> On Mon, Nov 7, 2011 at 4:38 PM, Supriya Kannery
> <address@hidden>  wrote:
> > On 11/04/2011 07:59 AM, Zhi Yong Wu wrote:
> > > On Sun, Oct 30, 2011 at 6:33 PM, Supriya Kannery
> > > <address@hidden>    wrote:
> > > > Currently cache setting of a block device cannot be changed
> > > > without restarting a running VM. Following patchset is for
> > > > enabling dynamic change of cache setting for block devices
> > > > through qemu monitor. Code changes are based on patches
> > > > from Christoph Hellwig and Prerna Saxena.
> > > >
> > > > This patchset introduces
> > > > a. monitor command 'block_set_hostcache' using which host
> > > >    pagecache setting for a block device can be changed
> > > >    dynamically.
> > >
> > > I got a bit confusion. Is it used to change host pagecache setting on
> > > hyperviser or on guest?
> > > This block device said by you is for guest, right?
> >
> >   This command is used for changing pagecache setting of
> > the image files in host which are acting as block devices
> > for guest.
> So what is the difference between it and cache option?

Cache=xx sets a combination of status flags for image files
among which host pagecache is just one. Intention here is
to gradually replace cache=xx with more explicit settings
like hostcache, flush, WCE.