Re: [Qemu-devel] [PATCH] migration: cache memory region ram ptr

[Paolo Bonzini]

Il 10/05/2014 18:32, Peter Lieven ha scritto:
> What about XEN?

You're right, Xen wouldn't work.  Your original patch would not break it 
just because Xen doesn't use migration (but the code would be broken).

You would have to cache qemu_get_ram_block rather than qemu_get_ram_ptr, 
move RAMBlock to memory-internal.h, and split the RAMBlock + ram_addr_t 
=> void * conversion out of qemu_get_ram_ptr and into a separate 
function (to be used by memory_region_get_ram_ptr).

I'm not sure of the benefit of your patch though.  qemu_get_ram_block 
already has a 1-item cache, are you seeing a low hit rate there?  Or any 
other profiling that shows qemu_get_ram_ptr as hot?

Paolo