Date: Sun, 6 May 2007 19:58:03 -0400 From: Garance A Drosehn <gad@FreeBSD.org> To: Peter Jeremy <peterjeremy@optushome.com.au>, Diomidis Spinellis <dds@aueb.gr> Cc: arch@FreeBSD.org Subject: Re: Accounting changes Message-ID: <p0624080bc26419ede26f@[128.113.24.47]> In-Reply-To: <20070506101020.GL825@turion.vk2pj.dyndns.org> References: <19235.1178303887@critter.freebsd.dk> <463BB88F.4020804@aueb.gr> <p06240809c262e5d7ac79@[128.113.24.47]> <463D9A7A.1080800@aueb.gr> <20070506101020.GL825@turion.vk2pj.dyndns.org>
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At 8:10 PM +1000 5/6/07, Peter Jeremy wrote: > > Garance A Drosehn wrote: > >>>I also wonder about using a time_t for ac_btime (starting time). >>>Now that we're running freebsd on very fast, multi-processor systems, >>>we might care whether "<this>-command" executed before "<that>-command", >>>and we might wish to have better resolution for the start-time of a >>>given command. > >On a multi-processor machine, both commands may have begun at the >same time (measured to whatever precision you want). Hmm. Well, that is a good point... >There are >occasional discussions regarding file timestamps (lack of precision >can confuse make) - which is a related issue. The decision as to >whether make ac_time a time_t or (eg) struct timespec is not obvious: >There is a definite space disadvantage to increasing ac_time precision >(though there's only one instance per accounting record so the problem >isn't as serious as comp_t). OTOH, I can see theoretical reasons for >wanting to know which command came first. > >This is probably a question that needs wider discussion: Has there >been any request for greater precision within the FreeBSD user >community? Not that I know of, but it might be that everyone is so used to the current resolution that they don't think much about changing it. Recently I have had a few cases where I was debugging something, and I did need time-resolution better than the nearest second. Admittedly those cases had nothing to do with these accounting records. However, I have had three separate cases where I've needed this in the past six months or so, and I don't think I've ever needed sub-second resolution before that. I don't know that we need better resolution for this version of the accounting-record format, but I suspect we will want it at some point in the future. -- Garance Alistair Drosehn = drosehn@rpi.edu Senior Systems Programmer or gad@FreeBSD.org Rensselaer Polytechnic Institute; Troy, NY; USA
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