Date: Fri, 26 Mar 2010 23:47:10 +0100 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: Peter Jeremy <peterjeremy@acm.org> Cc: freebsd-hackers@FreeBSD.org, Andriy Gapon <avg@icyb.net.ua> Subject: Re: periodically save current time to time-of-day hardware Message-ID: <861vf6n1jl.fsf@ds4.des.no> In-Reply-To: <20100326213022.GD32799@server.vk2pj.dyndns.org> (Peter Jeremy's message of "Sat, 27 Mar 2010 08:30:23 %2B1100") References: <4BACC791.70502@icyb.net.ua> <86zl1v84vy.fsf@ds4.des.no> <4BACD88E.2040803@icyb.net.ua> <86vdcj82qx.fsf@ds4.des.no> <20100326213022.GD32799@server.vk2pj.dyndns.org>
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Peter Jeremy <peterjeremy@acm.org> writes: > At least some versions of Linux also save a RTC drift approximation > and "last set" timestamp whenever the RTC is updated. This allows the > kernel to better set the system clock from the RTC at boot (ie, our > inittodr()). The downside is that this needs to store 8-16 bytes of > state somewhere non-volatile. Linux does this using an external > program and a file - but finding a location for a regularly updated > file that is read very early in the rc.d sequence might be problematic. We already do something similar for entropy. > that it _is_ updated. This suggests that an alternative approach > would be for adjtime() / ntp_adjtime() to directly call resettodr() if > it's more than P minutes since resettodr() was last called. ...if we want something like Linux's eleven-minute-mode. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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