On Wed, 17 Oct 2007, David Miller wrote: > > I believe that we have enough of a limited set of accessors to > sg->page that we can more aggressively encode things in the lower > bits. > > I'm thinking of encoding the low two bits of sg->page as > follows: > > 1) bits == 0 > > then the SG list is linear and sg_next() is sg++ > > 2) bits == 1 > > the nest SG is an indirect chunk, sg_next() is > therefore something like: > > next = *((struct scatterlist **)(sg + 1)); > > 3) bits == 2 > > this is the last entry in the scatterlist, sg_next() is NULL > > So for the cases of ARCH_HAS_SG_CHAIN not being set (ie. back > compatible), we can do no bit encoding in page->flags and just do > sg_next() == sg++, as is done now.
Yes, that sounds sane. Although I also wonder whether we want one global per-arch ARCH_HAS_SG_CHAIN, or perhaps have something more dynamic, which allows a per-SG-list choice (which in turn would require some kind of "head" entry that is passed into sg_next(), and in general descibes the SG list) Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/