Date: Tue, 18 Sep 2007 01:28:27 -0700 (PDT) From: Jeff Roberson <jroberson@chesapeake.net> To: Julian Elischer <julian@elischer.org> Cc: arch@freebsd.org Subject: Re: Changing p_swtime and td_slptime to ticks Message-ID: <20070918012555.G558@10.0.0.1> In-Reply-To: <46EF644E.9050207@elischer.org> References: <20070917165657.B558@10.0.0.1> <46EF644E.9050207@elischer.org>
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On Mon, 17 Sep 2007, Julian Elischer wrote: > Jeff Roberson wrote: >> Enclosed is a patch that fixes swapping with ULE. ULE has never properly >> set p_swtime and td_slptime which are used by the swapout/swapin code to >> select the appropriate thread to swap. > > I have not looked at in the depth required, but 2 points that I was unable > to check to my satisfaction before I got called away for work.... > > 1/ the source of the ticks is a monotonically increasing count that never > goes backwards or changes? ticks is incremented each time hardclock() is called. That's it. > > 2/ nothing that used to be accounted in seconds becomes accounted for in > ticks? I scale back to seconds where it is required. Really I think ticks would be the better metric in vm_glue.c but didn't want to make any drastic changes. Thanks, Jeff > > >> >> In 4BSD these two variables are increment once per-second as schedcpu() >> iterates over all threads. ULE does not have a once per-second loop >> iterating over all threads. So I have changed p_swtime to p_swtick and >> td_slptime to td_slptick. These record the value of 'ticks' when the >> thread slept or was last swapped in or out. >> >> For backwards compatibility I leave the values in kinfo_proc with the >> legacy meaning by subtracting from ticks and dividing by hz. I perform a >> similar transformation in the swapout code to convert to seconds. This >> change does make it possible to use sub-second granular decisions in the >> swap code, however I'm not sure if that's really necessary. >> >> So that I did not disturb the 4BSD mechanism I kept the original td_slptime >> in the td_sched area. It should be possible to use td_slptick directly but >> especially this close to release I did not want to change 4BSD. >> >> Feedback and testing welcome. >> >> Thanks, >> Jeff >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> freebsd-arch@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-arch >> To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org" >
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