Hollis Blanchard wrote: > On Fri, 2007-11-30 at 18:03 +0800, Zhang, Xiantao wrote: > >> Avi Kivity wrote: >> >>> Zhang, Xiantao wrote: >>> >>>>> Ah, I see. It isn't just the alignment. How do you allocate >>>>> kvm_vcpu, then? >>>>> >>>>> >>>> For evevy vm, we allocate a big chunk of memory for structure >>>> allocation. For vcpu, it should be always 64k aligned through our >>>> allocation mechanism. So, we don't care about its aligment issue :) >>>> >>>> >>> I see. Can you explain why you do that? Do you have a special >>> allocator in your guest-resident vmm module? >>> >> Since our VMM module and KVM module will share the kvm and vcpu >> structure, but VMM module has a different address space, so we have to >> use fixed allocation method to handle this share. For example, we >> allocates 1M memory(1M align) for every vm for this purpose in kvm >> module, and the first 64k is used for first vcpu of guest, and the >> second 64 for the second vcpu, and same for other vcpus. You can call >> it as special allocator or other names:) This is determined by IA64 >> virtualization architecture, and hard to workaround it in this >> host-based vm model. :( >> > > We're doing something similar with very large allocations. > > Currently, PowerPC's "vcpu" is actually a copy of the exception > handlers, plus the real vcpu data structure at a higher offset. Since > our exception handlers can't span 64KB regions, we allocate a full 64KB > for each vcpu. I'm not sure what benefit a kmem_cache would have in this > situation... > >
A kmem_cache is useful for specifying alignment, and as a general bookkeeping system. It's nice to see how many objects you have allocated in /proc/slabinfo, and it will automatically inform you if you have a leak when you unload the module. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
