Date: Tue, 5 Mar 2013 09:01:34 +0100 From: Luigi Rizzo <rizzo@iet.unipi.it> To: arch@freebsd.org, Davide Italiano <davide@FreeBSD.org>, Alexander Motin <mav@FreeBSD.org> Subject: tickless design guidelines Message-ID: <20130305080134.GC13187@onelab2.iet.unipi.it>
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Hi, i would like a bit of advice on how to get coarse time estimates (such as "no need to do anything unless at least X msec have elapsed") in a tickless kernel. In the past (and I mean a distant one, i got this habit back in 2.x), rather than calling get*time(), i used to look at "ticks" to see if it had changed, and only fetch the actual time accordingly. This worked well with HZ=1000 or above, when my required accuracy a few milliseconds. With tickless kernels, i am not sure anymore how often ticks gets updated. I may need to do this tests quite frequently (e.g. up to a million times per second), so I'd rather have some lightweight function. Any suggestion ? thanks luigi
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