Il 30/07/2012 01:50, Rusty Russell ha scritto: >> Also, being the first user of chained scatterlist doesn't exactly give >> me warm fuzzies. > > We're far from the first user: they've been in the kernel for well over > 7 years. They were introduced for the block layer, but they tended to > ignore private uses of scatterlists like this one. Yeah, but sg_chain has no users in drivers, only a private one in lib/scatterlist.c. The internal API could be changed to something else and leave virtio-scsi screwed... > Yes, we should do this. But note that this means an iteration, so we > might as well combine the loops :) I'm really bad at posting pseudo-code, but you can count the number of physically-contiguous entries at the beginning of the list only. So if everything is contiguous, you use a single non-indirect buffer and save a kmalloc. If you use indirect buffers, I suspect it's much less effective to collapse physically-contiguous entries. More elaborate heuristics do need a loop, though. Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
