[libvirt] [v4 0/9] Support cache tune in libvirt

[Marcelo Tosatti]

On Mon, Feb 13, 2017 at 03:42:04PM +0800, Eli Qiao wrote:
> > > L3data:0=0xff00;...
> > > L3code:0=0xff00;...
> > >  
> > > * Would you please help to test if the functions work.
> >  
> > Setting up CDP machine.
> >  
> > Unrelated:
> >  
> > Found a bug:
> >  
> > The code should scan for all directories in resctrlfs,
> > and then find free CBM space from that:
> >  
> >  
> > free_cbm_space = ~(resctrldir1.CBM_bits &
> > resctrldir2.CBM_bits &
> > ...
> > resctrldirN.CBM_bits)
> >  
> > For all resctrlfs directories.
> >  
> > The bug is as follows:
> >  
> > Create a directory in resctrlfs by hand:
> >  
> > # mkdir newres
> 
> Libvirt will not aware this after it starts running, so we should not allow operate /sys/fs/.

Are you saying that usage of the resctrlfs filesystem should not be
allowed after libvirt starts? I don't think this is correct.

> we will scan for all directors while the libvirt daemon begin running, and libvirt will remove exist directories if no tasks inside of it.  



> 
>   
> > # cd newres
> > # echo "L3:0=3;1=f0000" > schemata
> > # virsh start guest
> > # cd ../b4c270b5-e0f9-4106-a446-69032872ed7e
> > # cat schemata
> > L3:0=3;1=f0000
> >  
> > That is, it is using the same CBM space as the "newres"
> > reservation.
> >  
> >  
> 
> 
> As user create a new directory after libvirt running, it don’t notice newly created directory under /sys/fs/resctrl.
> 
> That will lead mess, this should be forbidden.  

Well, this means that only libvirt can use the resctrlfs filesystem.

This forbids other applications which require allocation
of CAT resources from being used. 

Its simple to fix it: move the scanning of resctrlfs data from libvirt
initialization time to:

	- VM initialization time
	and
	- virConnectGetCapabilities time

The second case is necessary to get updated free space information.