sounds good to me. On Tue, Mar 11, 2025 at 10:43 AM Russ Cox <r...@swtch.com> wrote:
> As far as the top-of-stack info, it gets complicated. You have to > hard-code an algorithm that must be implemented in every user binary, and > then it's a pain to change. This is why in Go we've backed away from > reading that info on Mac and why we call into the VDSO on Linux instead of > recreating that code ourselves. Personally, I'm not too worried about the > cost of fetching the time. A system call is fine. > > Based on this discussion, I've abandoned the idea of changing the system > calls, and I've updated Go to open /dev/bintime at startup and abandon > nsec. It also opens /dev/random at startup now too. If we're opening one, > two is not a big deal. That change is pending at https://go.dev/cl/656755. > > However, a change to Plan 9 is still needed to provide monotonic time. At > first I was going to try to recreate it from the ticks and fasthz values in > /dev/bintime, but the value of fasthz can change over time as aux/timesync > deems it necessary, and if fasthz goes up, then 1e9*ticks/fasthz will go > down, making the derived time non-monotonic. It is also annoying to do that > calculation efficiently: more parameters are needed from the kernel. > Instead of exposing all those parameters, it is far easier and cleaner to > have the kernel maintain a monotonic time and simply expose that. I suggest > we add the monotonic time in nanoseconds as an extra field you can read > from /dev/time and /dev/bintime. If you ask for a big enough buffer, you > get it. If not, you don't. The diff is here: > https://github.com/rsc/plan9/commit/baf076425c. > > Best, > Russ > *9fans <https://9fans.topicbox.com/latest>* / 9fans / see discussions > <https://9fans.topicbox.com/groups/9fans> + participants > <https://9fans.topicbox.com/groups/9fans/members> + delivery options > <https://9fans.topicbox.com/groups/9fans/subscription> Permalink > <https://9fans.topicbox.com/groups/9fans/T59810df4fe34a033-M94a3e524e0a77ddfec440be9> > ------------------------------------------ 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/T59810df4fe34a033-M1ca84cc218ac849453eac6b5 Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
