Date: Mon, 26 Mar 2007 21:29:38 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: deeptech71@gmail.com Cc: freebsd-chat@freebsd.org Subject: Re: 64bit timestamp Message-ID: <20070326182938.GA18096@kobe.laptop> In-Reply-To: <4607D66B.4070800@gmail.com> References: <200703251900.l2PJ0Z8w058298@lurza.secnetix.de> <4606D88E.4080503@gmail.com> <20070325215731.GA1517@kobe.laptop> <4607D66B.4070800@gmail.com>
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On 2007-03-26 16:19, deeptech71@gmail.com wrote: >Giorgos Keramidas wrote: >>On 2007-03-25 22:16, deeptech71@gmail.com wrote: >>> Actually, my intend wasn't to use it in filesystems, but >>> server-client apps, such as games, where 32bit integer timers >>> must be restarted every 3 weeks >> >> That's a bug in the applications themselves. The >> gettimeofday() call in any modern UNIX returns a `struct >> timeval', which contains *both* a time_t value of the current >> time with second-level accuracy and a tv_usec member with >> millisecond accuracy (or at least an approximation of a >> timestamp with millisecond accuracy). >> >> Any userlevel application which uses userlevel time counters >> and requires a restart every two or three weeks, because these >> userlevel timecounters have rolled back to zero, is broken and >> should be fixed. > > No, it's not a bug, the server and client communicates with > lots of packets timestamped with a synchronized time, and > sending 64bit timestamps would be too much bandwidth > consuming. There's a restart demand every hour or so, so it's > not a problem... but the server is limited for max 3 weeks. Well, if timestamps are required and the bandwidth is not enough to send 128 bits of timestamp data every few nanoseconds, then the operating system cannot do a lot of things to help. The best the OS can do is provide you *locally* with extra-fine timestamps, and let a smart algorithm of time synchronization between the two remote hosts handle the rest. It's not going to be easy, but someone has to do the "hard work" :)
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