Date: Tue, 08 Apr 1997 06:15:09 +0800 From: Peter Wemm <peter@spinner.DIALix.COM> To: Terry Lambert <terry@lambert.org> Cc: freebsd-current@freebsd.org Subject: Re: POLL & the Single FreeBSD'r Message-ID: <199704072215.GAA03730@spinner.DIALix.COM> In-Reply-To: Your message of "Mon, 07 Apr 1997 14:41:58 MST." <199704072141.OAA02263@phaeton.artisoft.com>
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Terry Lambert wrote: > > What you want is a high-resolution timer/sleep/schedule system, which we > > don't have, and nobody has offered to implement yet, so it's pretty > > unlikely that we'll see it in the near future. (This doesn't mean that it > > cannot be done, just that nobody has wanted it badly enough to do it. > > Messing with timers and a more precise sleep queue that can deal with the > > next event in microseconds for the timer programming might be enough, > > especially when combined with the RT schedule options) > > Yes; kernel preemtion on timer events before process quantum expiration > is probably 90% of the way to real RT support... > > I don't necessarily want something with high-resoloution timing right > now, but the select() code *will* operate sub-quantum if there's nothing > else in the run queue without "real" high resoloution support. SunOS 4.x > has historically worked that way (down to 4uS on a select/timeout buzz > loop on a SPARCStation 1+, actually... better on faster hardware). Hmm.. this is an interesting suggestion.. I think we can do the same with some careful use of microtime() and mi_switch().. > scheduler can't keep up, then it can't keep up (the part of the man > page I was referrung to was the tv_usec reference). peter@spinner[6:07am]~src/sys/kern-132> man select | col -b | grep tv_ peter@spinner[6:11am]~src/sys/kern-133> What tv_usec reference? Are you on the wrong system? :-) Our 4.4BSD derived man page only says the word "timeout" and mentions nothing about tv_* at all > Regards, > Terry Lambert > terry@lambert.org Cheers, -Peter
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