> >
> > This translates to the following resctrltool-style reservations:
> >
> >         res.vm-a.vcpu-2
> >
> >                 type=both,size=VM-A-RESSIZE,cache-id=0
> >
> >         res.vm-b.vcpu-2
> >
> >                 type=both,size=VM-B-RESSIZE,cache-id=0
> >
> > Which translate to the following in resctrlfs:
> >
> >         res.vm-a.vcpu-2
> >
> >                 type=both,size=VM-A-RESSIZE,cache-id=0
> >                 type=both,size=default-size,cache-id=1
> >                 ...
> >
> >         res.vm-b.vcpu-2
> >
> >                 type=both,size=VM-B-RESSIZE,cache-id=0
> >                 type=both,size=default-size,cache-id=1
> >                 ...
> >

> > Which is what we want, since the VCPUs are pinned.
> >
> >
> > res.vm-a.vcpu-1 and res.vm-b.vcpu-1 don't need to
> > be assigned to any reservation, which means they'll
> > remain on the default group.
>
> You've showing type=both here which IIUC, means data
> and instruction cache.

No, type=both is non-cdp hosts (data and instructions
reservations shared).

type=data,type=code is for cdp hosts (data and instructions
reservations separate).

> Is that configuring one cache
> that serves both purposes ?

Yes.

> Do we need to be able
> to configure them independantly.

Yes.

> > RESTRICTIONS TO THE SYNTAX ABOVE
> > ================================
> >
> > Rules for the parameters:
> > * type=code must be paired with type=data entry.
>
> What does this mean exactly when configuring guests ? Do
> we have to configure data + instruction cache on the same
> cache ID, do they have to be the same size, or are they
> completely independant ?

This means that a user can't specify this reservation:

        type=data,size=10mb,cache-id=1

They have to specify _both_ code and data
sizes:

        type=data,size=10mb,cache-id=1;
        type=code,size=2mb,cache-id=1

Now a single both reservation is valid:

        type=both,size=10mb,cache-id=1

> > ABOUT THE LIST INTERFACE
> > ========================
> >
> > About an interface for listing the reservations
> > of the system to OpenStack.
> >
> > I think that what OpenStack needs is to check, before
> > starting a guest on a given host, that there is sufficient
> > space available for the reservation.
> >
> > To do that, it can:
> >
> >         1) resctrltool list (the end of the output mentions
> >            how much free space available there is), or
> >            via resctrlfs directly (have to lock the filesystem,
> >            read each directory, AND each schemata, and count
> >            number of zero bits).
> >         2) Via libvirt
> >
> > Should fix resctrltool/API to list amount of contiguous free space
>
> OpenStack, should just use libvirt APIs exclusively - there should not
> be any need for it to use other tools if we've designed the libvirt API
> correctly.

Got it.

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