Date: Tue, 18 Sep 2007 14:22:58 -0700 (PDT) From: Jeff Roberson <jroberson@chesapeake.net> To: Andre Oppermann <andre@freebsd.org> Cc: arch@freebsd.org, Julian Elischer <julian@elischer.org> Subject: Re: Changing p_swtime and td_slptime to ticks Message-ID: <20070918142115.C558@10.0.0.1> In-Reply-To: <46EFE4BD.4030505@freebsd.org> References: <20070917165657.B558@10.0.0.1> <46EF644E.9050207@elischer.org> <20070918012555.G558@10.0.0.1> <46EFE4BD.4030505@freebsd.org>
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On Tue, 18 Sep 2007, Andre Oppermann wrote: > 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. Thanks Andre, this is a good point. For the td_slptime I don't think it's of practical concern. However, for swtime I think I will convert it then to seconds from boot. Jeff > > -- > Andre >
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