24c8af8da8
The previous fix was unnecessarily very slow up to 105 hours where the simple formula used previously worked, and unnecessarily slow by a factor of about 5/3 up to 388 days, and didn't work above 388 days. 388 days is not a long time, since it is a reasonable uptime, and for processes the times being calculated are aggregated over all threads, so with N CPUs running the same thread a runtime of 388 days is reachable after only 388 / N physical days. The PRs document overflow at 388 days, but don't try to fix it. Use the simple formula up to 76 hours. Then use a complicated general method that reduces to the simple formula up to a bit less than 105 hours, then reduces to the previous method without its extra work up to almost 388 days, then does more complicated reductions, usually many bits at a time so that this is not slow. This works up to half of maximum representable time (292271 years), with accumulated rounding errors of at most 32 usec. amd64 can do all this with no avoidable rounding errors in an inline asm with 2 instructions, but this is too special to use. __uint128_t can do the same with 100's of instructions on 64-bit arches. Long doubles with at least 64 bits of precision are the easiest method to use on i386 userland, but are hard to use in the kernel. PR: 76972 and duplicates Reviewed by: kib |
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| kerberos5 | ||
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| release | ||
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| sys | ||
| targets | ||
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| usr.bin | ||
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| .arcconfig | ||
| .arclint | ||
| .gitattributes | ||
| .gitignore | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.libcompat | ||
| Makefile.sys.inc | ||
| ObsoleteFiles.inc | ||
| README | ||
| README.md | ||
| UPDATING | ||
FreeBSD Source:
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