Date: Tue, 18 Sep 2007 16:46:21 +0200 From: Andre Oppermann <andre@freebsd.org> To: Jeff Roberson <jroberson@chesapeake.net> Cc: arch@freebsd.org, Julian Elischer <julian@elischer.org> Subject: Re: Changing p_swtime and td_slptime to ticks Message-ID: <46EFE4BD.4030505@freebsd.org> In-Reply-To: <20070918012555.G558@10.0.0.1> References: <20070917165657.B558@10.0.0.1> <46EF644E.9050207@elischer.org> <20070918012555.G558@10.0.0.1>
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Jeff Roberson wrote: > 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. ticks is 2^31 on x86 and at HZ=1000 is wraps within a reasonable short uptime. You have to make sure that your code handles that correctly or you run into lots of strange effects which are almost impossible to reproduce. In TCP we've got bitten by that. -- Andre
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