Date: Mon, 7 Sep 2009 01:15:38 -0400 (EDT) From: Garrett Wollman <wollman@hergotha.csail.mit.edu> To: rizzo@iet.unipi.it Cc: arch@freebsd.org Subject: Re: incorrect usleep/select delays with HZ > 2500 Message-ID: <200909070515.n875Fct3048327@hergotha.csail.mit.edu> In-Reply-To: <20090906155154.GA8283@onelab2.iet.unipi.it>
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In article <20090906155154.GA8283@onelab2.iet.unipi.it> you write: >(this problem seems to affect both current and -stable, >so let's see if here i have better luck) > >I just noticed [Note 1,2] that when setting HZ > 2500 (even if it is >an exact divisor of the APIC/CPU clock) there is a significant >drift between the delays generated by usleep()/select() and those >computed by gettimeofday(). In other words, the error grows with >the amount of delay requested. If I may be so bold as to suggest: if you think you want HZ > 1000, you're probably wrong. -GAWollman -- Garrett A. Wollman | What intellectual phenomenon can be older, or more oft wollman@bimajority.org| repeated, than the story of a large research program Opinions not shared by| that impaled itself upon a false central assumption my employers. | accepted by all practitioners? - S.J. Gould, 1993
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