Your document is not accessible to me. (Google-internal?) On Wed, Feb 1, 2017 at 5:18 PM, 'Keith Randall' via golang-nuts <golang-nuts@googlegroups.com> wrote: > I wrote up a proto-proposal for something like this a while ago. > > https://docs.google.com/a/google.com/document/d/18nu6QTr-ACYr5AiyP6x31SkXvuJZZaZ12lnvPTEQfgQ/pub > > It has a few numbers worth looking at in it. > > This proposal was before the fully precise GC we have today. It needs to > have special GC marking bits for string pointer words (like we did for > interface data words so long ago: go1.3ish). I'm not sure we could get it > to work today. > > On Wednesday, February 1, 2017 at 10:46:05 AM UTC-8, Ian Lance Taylor wrote: >> >> On Wed, Feb 1, 2017 at 10:38 AM, Eliot Hedeman >> <eliot.d...@gmail.com> wrote: >> > Ok, I'm going to try to restate the issues raised and answer them one by >> > one. If I misunderstand, please let me know. >> > >> > 1. The GC needs to know if a pointer is actually a pointer. >> > Solution: Check if the high bit is set. If it is, you know for sure that >> > it >> > is not a pointer. >> > It actually doesn't matter if the cpu ignores the top 16 bits or not. >> > The >> > point is that the top 8 bits will never be used in an actual pointer, >> > and >> > that is all we care about for this implementation. >> >> It's not that simple. At least on Solaris amd64, the high bit will be >> set for a pointer into the stack. >> >> > 2. This only works for x86-64 >> > Solution: I don't even think it is hyperbolic to say that 99% of all go >> > running in production is on x86-64. So even if this optimization is only >> > implemented for x86-64, it is well worth it. The rest could be take care >> > of >> > by a stubbed out isSmallString(s string) bool that always returns false, >> > and >> > let the compiler remove all the small string code from the resulting >> > binary. >> >> I suppose we could do that but I would consider it very unfortunate. >> >> Ian > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout.
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