In message <[EMAIL PROTECTED]>, "M. Warner Losh" writes: >In message: <[EMAIL PROTECTED]> > Ashley Yakeley <[EMAIL PROTECTED]> writes:
>OSes usually deal with timestamps all the time for various things. To >find out how much CPU to bill a process, to more mondane things. >Having to do all these gymnastics is going to hurt performance. One >might scoff at this statement, but research into performance problems >and issues has found time and again timekeeping and timestamps to have >a surprisingly large impact. So for the foreseeable future, >timestamps in OSes will be a count of seconds and a fractional second >part. That's not going to change anytime soon even with faster >machines, more memory, etc. Too many transaction processing >applications demand maximum speed. I will agree with Warner here, but I will add the footnote that since silicon pushers seem to be at a loss for how to gainfully employ silicon these days, we are not particular insistent on any particular aspect of the timestamps, apart from them being cheap to get, add, subtract and compare. If the silicon designers want to build in support for YYYYMMDDHHMMSS.mmmuuunnnppp BCD encoded timestamps, as long as they provide us with cheap instructions to carry out the above operations, we're happy. I should caution any hopes however, by mentioning that at this time I have yet to see any CPU design getting a binary counter running at a predictable rate right in first try. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.