Re: [Libvir] Start NUMA work

On Tue, Sep 11, 2007 at 04:28:00PM +0100, Richard W.M. Jones wrote: > Daniel Veillard wrote: > > Okay enclosed is a first patch to add the new entry point for getting > >the available memeory in the NUMA cells: > > > >/** > > * virNodeGetCellFreeMemory: > > * @conn: pointer to the hypervisor connection > > * @freeMems: pointer to the array of unsigned long > > * @nbCells: number of entries available in freeMems > > * > > * This call allows to ask the amount of free memory in each NUMA cell. > > * The @freeMems array must be allocated by the caller and will be filled > > * with the amounts of free memory in kilobytes for each cell starting > > * from cell #0 and up to @nbCells -1 or the number of cell in the Node > > * (which can be found using virNodeGetInfo() see the nodes entry in the > > * structure). > > * > > * Returns the number of entries filled in freeMems, or -1 in case of > > error. > > */ > > > >int > >virNodeGetCellsFreeMemory(virConnectPtr conn, unsigned long *freeMems, > > int nbCells) > > So you're using "unsigned long" here to mean 32 bits on 32 bit archs, > and 64 bits on 64 bit archs? > > A purely 32 bit freeMem will allow up to 4095 GB of RAM per cell. But > in reality up to 2047 GB of RAM because mappings in other languages will > probably be signed. > > High-end users are already decking out PCs with 128 GB of RAM. If they > double the RAM every year, we'll hit this limit in 4 years[1]. So is it > worth using an explicit 64 bit quantity here, or using another base (MB > instead of KB for example)? Or do we just think that all such vast > machines will be 64 bit? Well we already use unsigned long in KB for memory quantities in libvirt, I just reused that, I doubt we will see more than 64GB for 32bits CPU ever, that's already stretching the limits