Date: Tue, 18 Sep 2007 15:37:14 -0700 (PDT) From: Jeff Roberson <jroberson@chesapeake.net> To: Andre Oppermann <andre@freebsd.org> Cc: arch@freebsd.org, Julian Elischer <julian@elischer.org> Subject: 64bit ticks, was Re: Changing p_swtime and td_slptime to ticks Message-ID: <20070918153536.D558@10.0.0.1> In-Reply-To: <20070918142115.C558@10.0.0.1> References: <20070917165657.B558@10.0.0.1> <46EF644E.9050207@elischer.org> <20070918012555.G558@10.0.0.1> <46EFE4BD.4030505@freebsd.org> <20070918142115.C558@10.0.0.1>
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On Tue, 18 Sep 2007, Jeff Roberson wrote: > 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. Is there a good reason for not making ticks 64bit? math involving this value is relatively infrequent. Bruce? Any comments? It'd sure let us forget all of these counter wrapping problems. Thanks, Jeff > > Jeff > >> >> -- >> Andre >> > _______________________________________________ > 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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