Date: Fri, 19 Oct 2001 08:23:46 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Alex Levine <sashkin@home.com> Cc: freebsd-hackers@FreeBSD.org Subject: Re: Possible bug in scheduler. Message-ID: <XFMail.011019082346.jhb@FreeBSD.org> In-Reply-To: <3BCFD1CB.10609@home.com>
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On 19-Oct-01 Alex Levine wrote: > John Baldwin wrote: > >>On 18-Oct-01 Alexander Langer wrote: >> >>>Thus spake Alex Levine (sashkin@asplinux.ru): >>> >>>>resetpriority() calls maybe_resched() at the end after updating p_usrpri >>>>based on changed p_estcpu. >>>>maybe_resched() uses curpriority_cmp to compare priorities of current >>>>and given process and this function ( curpriority_cmp ) uses p_priority >>>>which is unchanged yet - the new p_usrpri is not reflected to p_priority >>>>yet. >>>> >>>In -CURRENT, it's more obvious: >>>maybe_resched() only rescheds, if the resetted process' priority >>>level changes. >>> >>>Since resetpriority() doesn't modify the priority level but >>>only the user priority, the call to maybe_resched() has no >>>effect at all -- only some overhead for the comparisons >>>(curproc will have had the higher or same priority level >>>as the resetted process anyways, otherwise it hadn't been curproc :) >>> >>>So, either >>> - p's priority level in resetpriority has to be re-calculted >>> as well, or >>> - the call to maybe_resched() can be removed w/o loss >>> of functionality. >>> >> >> >>or c) in the preemptive kernel maybe_resched() doesn't exist as it's >>functionality is more properly handled in other places. >> > I took another look in CURRENT. The same call to maybe_resched from > reset_priority is as useless as in STABLE. Only there the recalculation > relies on pri_level, which replaced p_priority as I understand but the > thing which is being changed is usr_pri. So it's the same. Yes, but in the uncommitted (b/c it's not fully stable and I need to update the patches) preemptive kernel, it doesn't exist. :) So it will be fixed in -current by removing it in favor of something else. -- John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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