Date: Sat, 14 Aug 1999 17:02:35 +1000 From: Bruce Evans <bde@zeta.org.au> To: BMCGROARTY@high-voltage.com, peter@netplex.com.au Cc: alc@cs.rice.edu, blanquer@cs.ucsb.edu, freebsd-smp@FreeBSD.ORG Subject: Re: Questions Message-ID: <199908140702.RAA16805@godzilla.zeta.org.au>
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>This lack of granularity really sucks and hurts a lot when running things like >rc5des etc in the background, even on a single cpu system. It's very >spectacular when you have a graphical program running. For one second, it >runs at full speed. The next second, it runs at half speed as it's sharing >the top run queue with rc5des. Then, it's back to full speed again, and so >on every second. > >I made a few tweaks here a while ago to enable speeding up the scheduler >that fixed this, but bde said he had other patches to fix it properly. I Other patches to fix other scheduling bugs. I was still looking for the major bug that let rc5des (or any process) run in preference to higher priority processes on systems with shared PCI, EISA) irqs. >ended up frying my patch set somehow and never got back to it. When bde >committed his changes, it made little difference here. I think it now takes I never got back to committing my other patches. >1/4 of a second for the lower priority process to loose the top priority now. >I think the SMP "BETTER_CLOCK" stuff does similar things. statclock() calls resetpriority() for every 4 user-mode calls, i.e., every 1/32 seconds while user processes are active. Perhaps it takes 8 calls for the changes to affect the run queues (maybe 4 for the priority granularity and 1 for a bug that I haven't committed the fix for yet?). 1/4 second isn't as long as it used to be :). The magic mask of 3 in statclock() should depend on the frequency of statclock(). Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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